Deboer v Kolyn: Missed Breast Cancer, Discordant Biopsies, and the Tumour Biology Defence

Janice DeBoer was 45 years old in the summer of 2009 when she noticed a lump in her right breast. She had felt lumps before; she had even had two fibroadenomas removed from her breasts in 2002 under the care of the same surgeon, Dr. Kolyn. She went for imaging. A radiologist assessed her mammogram as “probably benign.” Her surgeon, relying on that assessment, did not order further imaging. When a new lump appeared in the same breast, the surgeon biopsied it without image guidance, got a discordant result, and did not act on it. In the meantime, Mrs. DeBoer went ahead with breast augmentation surgery. During that surgery, both lumps were removed and sent for pathology. The pathology returned: invasive ductal carcinoma.

Nine months had passed since her first mammogram. In those nine months, Mrs. DeBoer’s cancer had progressed from a highly curable Stage I tumour to a Stage II, multifocal, lymph node positive disease. The breast augmentation surgery complicated the mastectomy that followed. Scar tissue and fibrous adhesions made it impossible to achieve clear surgical margins. Chemotherapy was made less effective. There was local chest wall recurrence. Then bone metastases. By the time of trial, Mrs. DeBoer had incurable Stage IV breast cancer. She had been forced to resign from the career as a flight attendant she had held for over 30 years.

She was going to die of this disease.

Deboer v Kolyn is a case about two physicians who failed at sequential points in the diagnosis of breast cancer, and about what the law requires when defendants argue that biology, not negligence, was the real cause of the patient’s outcome.

The Parties and the Clinical History

Janice DeBoer had been a patient of the general surgeon Dr. D. M. Kolyn since 2001, when she was first referred for what turned out to be a benign breast lump. Dr. Kolyn performed an excision of two fibroadenomas in May 2002 at Cambridge Memorial Hospital. There were no problems.

In mid-2009, at the age of 45, Mrs. DeBoer again noticed a lump, this time in the right breast at approximately the five o’clock position (Morissette J. described clock positions as viewed from the front, twelve at the top, three at the right, six at the bottom, nine at the left). Her family doctor, Dr. Hankinson, referred her for a mammogram and ultrasound, performed on July 22, 2009. Dr. Tsin, a radiologist, reviewed the imaging and produced his report on August 1, 2009.

Dr. Tsin’s report noted that Mrs. DeBoer had dense breasts and that there were “coarse cluster microcalcifications in the right breast on the medial lateral view only along the inferior right breast adjacent to the chest wall and not seen on craniocaudal view.” Using the American College of Radiology’s BI-RADS (Breast Imaging Reporting and Data System) scale (which runs from 0 (indeterminate) through 5 (highly suspicious)), he rated the imaging as BI-RADS 3: “probably benign.” He recommended a follow-up ultrasound in six months and a follow-up mammogram in a year.

Mrs. DeBoer attended her family doctor on September 23, 2009 to review the results. She wanted the lump removed because of discomfort. Dr. Hankinson referred her back to Dr. Kolyn, whose referral note read: “Lady with R sided breast lump that is causing some pain. Your management please.”

Dr. Kolyn received the referral and Dr. Tsin’s imaging report. She relied on the report’s “likely benign” characterization and scheduled an appointment with Mrs. DeBoer for December 21, 2009, almost three months later.

December 2009 to May 2010: A Series of Missed Opportunities

December 21, 2009: The First Appointment

When Mrs. DeBoer presented to Dr. Kolyn in December 2009, she described the lump as “hard and lumpy” and as “different than the fibroadenomas that she had in the past.” She had had the lump for over five to six months. Dr. Kolyn performed a physical examination and formed a plan to remove the lump under local anesthesia on February 16, 2010. She did not believe further imaging was required, given that plan. She took Dr. Tsin’s imaging report “at face value.”

February 16, 2010: A New Lump and a Blind Biopsy

When Mrs. DeBoer returned on February 16, 2010, she reported a new area of concern, at approximately the seven o’clock position in the right breast. Dr. Kolyn examined the new area and could palpate it. She decided to perform a Trucut needle biopsy of this new lump. She did not use real-time ultrasound guided imaging to confirm she was biopsying the correct lesion. She deferred excision of the original five o’clock lump pending pathology results from the seven o’clock biopsy.

The three cores of tissue obtained in the blind biopsy produced a pathology report showing “benign breast tissue without specific abnormality.” Critically, the pathologist added a note: “clinical and radiographical correlation is required to determine if the appropriate lesion has been biopsied.”

Dr. Kolyn did not order further imaging. She did not biopsy the five o’clock lump. She did not seek the correlation the pathologist had specifically required. She scheduled Mrs. DeBoer for a clinical follow-up on March 23, 2010, a date that was later rescheduled to April 22, 2010 for surgical removal of both lumps.

April and May 2010: The Breast Augmentation

In early April 2010, Mrs. DeBoer called Dr. Kolyn’s office to ask about the risk of infection from the scheduled April 22 lump removal, because she had breast augmentation surgery planned with Dr. Kaila, a plastic surgeon, on May 3, 2010. Dr. Kolyn’s secretary recorded the call. Dr. Kolyn decided the augmentation surgery was too close to the scheduled lump removal and rescheduled the lump removal to August 9, 2010. She did not advise against the breast augmentation surgery. She did not order further imaging before the rescheduled removal date. She did not biopsy the five o’clock lump.

Mrs. DeBoer went ahead with the breast augmentation on May 3, 2010. During that surgery, Dr. Kaila identified the two lumps Mrs. DeBoer had described and removed them, sending both in the same container for pathology. The pathology report identified invasive ductal carcinoma. The lumps that Dr. Kolyn had been planning to address “eventually” had contained cancer all along.

The Cancer and Its Consequences

Dr. Kolyn was shocked when she reviewed the pathology. She met with Mrs. DeBoer and her husband on May 20, 2010. Fine needle aspiration of the right axillary lymph node on June 1, 2010 confirmed metastatic carcinoma in the lymph nodes. An MRI on June 17, 2010 showed enhancing nodules in all four quadrants of the right breast, suspicious for multicentric malignancy.

Dr. Kolyn performed a right modified radical mastectomy on June 30, 2010. The surgery was complicated. Mrs. DeBoer had wanted to keep her implants if possible. Dr. Kolyn encountered significant scar tissue and fibrosis from the prior breast augmentation surgery, with extreme adherence of breast tissue to the implant capsule. Positive margins were left at the end of the mastectomy. The pathology revealed cancer in multiple areas of the right breast, along with ductal carcinoma in situ (DCIS) and lymph node involvement.

Mrs. DeBoer’s cancer was hormone receptor positive (estrogen and progesterone receptor positive) and HER2neu negative, tumour characteristics that, in a different world, would have been excellent prognostic markers for a fully curative outcome. She was referred to medical oncology and radiation oncology for further treatment.

What followed was a prolonged, painful, and ultimately unsuccessful course of treatment. Chemotherapy until November 2010. Side effects including hospitalizations and depression. A prescribed course of Tamoxifen (an anti-estrogen therapy) that Mrs. DeBoer did not take as directed: she filled one prescription, started it briefly in 2011, and did not take it at all in 2012, despite repeated recommendations from her oncologist. Radiation in July 2011 for a local chest wall recurrence: she completed 21 of the 25 planned treatments. Bone metastases in November 2013. Her ovaries removed in 2014. Shoulder metastases in 2016. By the time of trial, Mrs. DeBoer had incurable Stage IV breast cancer, had resigned from her job as an Air Canada flight attendant, and was living with chronic pain and disability.

The Standard of Care Findings

The Radiologist: Dr. Tsin

The plaintiffs called Dr. Sparrow, with 40 years of radiological practice, founding membership in the Ontario Breast Cancer Screening Program, and the Chair of the Canadian Association of Radiologists Mammography Accreditation Program. He was the only expert who testified on the radiologist’s standard of care. The defence called no radiology expert.

Dr. Sparrow testified that Dr. Tsin’s BI-RADS 3 rating was a breach of the standard of care. The appropriate rating was BI-RADS 4 (“suspicious”) for four cumulative reasons: this was a diagnostic mammogram (ordered in response to a palpable lump), not a routine screening mammogram; Mrs. DeBoer was premenopausal and under 50; she had a palpable lump; and she had dense breasts. In combination, these factors required heightened clinical concern. The calcifications themselves were heterogeneous (irregular in shape rather than the uniform appearance of benign calcifications), and their distribution was segmental, following a ductal pattern toward the nipple, rather than diffuse or bilateral.

Dr. Tsin defended his rating by characterizing the calcification distribution as “regional,” flowing downward against the chest wall rather than in a segmental ductal pattern. Morissette J. rejected this evidence. The only way to make that determination reliably was through additional magnification imaging that Dr. Tsin had not ordered. Significantly, the imaging report sent to Dr. Kolyn had incorrectly indicated that a “coned mag bilateral view” had been conducted, an annotation made by a clerk that was not accurate. Dr. Tsin only became aware of this inaccuracy when producing his file for litigation.

The court found Dr. Tsin’s evidence about the calcification distribution could not stand as reasonable. It preferred Dr. Sparrow’s opinion that the calcifications appeared to be segmental along a ductal pattern. Dr. Tsin breached the standard of care by failing to request further imaging (supplemental cranial caudal images and magnification views) and by assigning a BI-RADS 3 rating when a BI-RADS 4 was required. Had further imaging been ordered, it would have occurred within two to three weeks of July 30, 2009. A subsequent biopsy would have followed. Mrs. DeBoer would have been diagnosed approximately eight months before she was.

The Surgeon: Dr. Kolyn

Dr. Holliday, plaintiff’s expert, had 36 years of general surgical practice in London, Ontario, including the last ten focused on breast cancer. He was Professor Emeritus at Western, had treated 1,500 to 2,000 breast cancer patients, and held senior roles in national surgical credentialing. Dr. Davison, defence expert, practised in a community setting in Brampton with no academic appointment and publications not related to breast cancer.

Morissette J. noted the contrast without elaborate comment; the difference in credentials was relevant context for weighing their competing opinions. She accepted Dr. Holliday’s evidence on each point of dispute.

Three distinct failures were established against Dr. Kolyn. First, the blind biopsy. Using real-time ultrasound guidance when biopsying a small, deep lump is required because the biopsy needle can push an unanchored lump away rather than penetrate it. A blind Trucut biopsy of a small deep lesion cannot confirm the correct lesion has been sampled. Dr. Holliday’s evidence was that image localization was required; Dr. Davison’s that an immediate blind biopsy was reasonable. The court preferred Dr. Holliday.

Second, and critically, the discordant findings. The pathology report from the blind biopsy showed only benign breast tissue: no microcalcifications, no features of fibroadenoma, no suspicious tissue. And the pathologist had explicitly noted that “clinical and radiographical correlation is required to determine if the appropriate lesion has been biopsied.” These were discordant findings. The pathology results were inconsistent with the clinical presentation (a new hard lump) and with the ultrasound findings. A result showing only non-specific benign tissue, combined with an explicit pathologist’s note that correlation was required, should have prompted Dr. Kolyn to recognize that she may not have biopsied the correct lesion. Instead, she took the benign result as confirmation of her prior clinical impression and scheduled the lumps for eventual removal. She attributed the benign result at trial to her belief that the new lump was “hormonal thickening,” but Morissette J. rejected this post-hoc explanation. The word “lump” appears three times in Dr. Kolyn’s contemporaneous notes. “Thickening” and “hormonal” appear nowhere.

Third, the five o’clock lump received no further investigation after the July 2009 imaging; over six months passed with no repeat imaging or biopsy of the original lesion. When the breast augmentation surgery was approaching, Dr. Kolyn had every reason to ensure the clinical picture was clear before May 3. The knowledge of the upcoming augmentation should have been an additional trigger for imaging in February or early March 2010. Instead, Dr. Kolyn’s attention had been diverted to the new seven o’clock lump, with the original five o’clock lump simply scheduled for removal “eventually.”

How the Breast Augmentation Surgery Complicated Everything

Both surgical experts agreed that the breast augmentation surgery materially complicated the management of Mrs. DeBoer’s cancer. Dr. Kolyn’s operative notes from the mastectomy described extreme fibrosis and adherence of the breast tissue to the implant capsule. The scar tissue and fibrous adhesions created a technically difficult dissection, made clear margins harder to achieve, and resulted in positive margins being left behind, meaning cancer cells remained on the chest wall. Positive margins contributed directly to the local recurrence in 2011.

The complications ran deeper than the surgical difficulty. Dr. Potvin explained that systemic chemotherapy works by reaching tumour cells through the blood supply. The scarring and fibrosis caused by the augmentation surgery, compounded by the mastectomy through already-altered tissue planes, resulted in a poor blood supply to the tumour bed. This reduced the tumoricidal effectiveness of chemotherapy. Anti-hormonal therapy was similarly compromised in its ability to reach residual cancer cells.

The counterfactual was stark: had Mrs. DeBoer been diagnosed in the fall of 2009 and had her mastectomy at that point (before the augmentation surgery), the tissue planes would have been clean and identifiable. Clear margins would have been achievable. Systemic therapies would have been effective. The cancer was curable.

The Causation Battle: Tumour Biology vs. the Clinical Evidence

The Defence Theory: Aggressive Biology

The core of the defence causation case was that Mrs. DeBoer’s cancer had an inherently aggressive biology: that it had already spread microscopically into the bloodstream at a level undetectable by any available test as early as July 2009. On this theory, earlier diagnosis would have caught the same disease at essentially the same stage of systemic spread, and the difference in outcome would have been minimal or non-existent, certainly not enough to cross the balance of probabilities threshold.

Dr. Fine, the defendants’ expert, supported this theory by pointing to the relatively rapid local recurrence in 2011, only about a year after the mastectomy. He also relied on the cancer’s histological grade 3 classification. In his view, a recurrence that early indicated a cancer with aggressive biological behaviour, one that had probably already seeded distant micrometastases before any diagnosis date that might have been achieved through proper care. He calculated the difference in ten-year survival rate as minimal (perhaps less than ten percent) and submitted this did not reach the balance of probabilities required for causation in law.

The court rejected this theory, for reasons rooted in the specific clinical evidence of Mrs. DeBoer’s cancer.

The Plaintiff’s Evidence: The Biology Said Otherwise

Mrs. DeBoer’s cancer was estrogen and progesterone receptor positive (ER+PR+) and HER2neu negative. These are biological markers associated with hormone-sensitive cancer, a type that responds well to anti-hormonal treatment (such as Tamoxifen), tends to grow more slowly than hormone-insensitive variants, and tends, when it does spread, to go to bones rather than to vital organs like the liver or lungs. All of this was consistent with what Mrs. DeBoer actually experienced: her cancer spread to her bones but not to her vital organs; she was still alive seven years post-diagnosis; when she finally took Tamoxifen consistently in 2013, it was effective. As Dr. Potvin explained, truly aggressive, biologically high-grade cancers typically metastasize to vital organs and cause death within the first couple of years following diagnosis. Mrs. DeBoer’s disease trajectory was inconsistent with the aggressive biology Dr. Fine described.

Furthermore, no Onco-Type DX test had been conducted, the genetic profiling test that would have provided objective evidence of the cancer’s biological aggressiveness. Morissette J. drew an adverse inference from the defendants’ failure to obtain this evidence. The aggressive biology theory was Dr. Fine’s central argument. The Onco-Type DX test could have supported or undermined that argument. It was within the defendants’ power to have the test done. They did not. Dr. Fine acknowledged in cross-examination that a histological grade 3 tumour (which Mrs. DeBoer had) can have a low Onco-Type DX score, meaning histological grade alone does not establish the aggressive biology he theorized. In the absence of testing that could have confirmed his theory, and in the presence of clinical evidence inconsistent with aggressive behaviour, the court found his opinion was founded on speculation.

The “Loss of Chance” Argument: Statistical Evidence and Legal Causation

The defence also argued that even accepting an earlier diagnosis would have produced a better outcome for Mrs. DeBoer, the statistical difference in survival probability was too small (perhaps ten percent or less) to constitute causation on the balance of probabilities. Loss of chance is not compensable in Canadian medical malpractice law (the principle from Lawson v Laferriere), and a ten percent difference does not rise to a fifty percent threshold.

Morissette J. addressed this directly. Statistical evidence, while informative in the medical oncological context, is less helpful in determining legal causation. Where statistical evidence does not rise to a scientific balance of probabilities, causation in law may nonetheless exist where the totality of evidence in the specific case supports a finding of causation on the balance of probabilities. The court cited Laferriere v Lawson, 1991 CanLII 87 (SCC), [1991] 1 SCR 541 at para 164 for this proposition.

The causation conclusion in Deboer v Kolyn did not rest on population statistics. It rested on the specific evidence about this specific patient: Stage I cancer in the summer of 2009 that was diagnosable, treatable, and curable; nine months of delay; Stage II cancer with lymph node involvement and multicentric disease at diagnosis; augmentation surgery that complicated the mastectomy and compromised chemotherapy effectiveness; local recurrence; bone metastases; and a woman who was now dying of a disease she should have survived. The finding was that but for the defendants’ negligence, Mrs. DeBoer would not be suffering from bone metastases. She would still be working. She would not die prematurely from this disease.

Failure to Mitigate: The 18% Reduction

The defendants raised failure to mitigate in respect of two post-diagnosis treatment decisions. Mrs. DeBoer had been prescribed Tamoxifen (an anti-estrogen therapy known to be effective against her hormone receptor positive cancer), but she filled only one prescription, started it briefly in 2011, and did not take it at all in 2012, contrary to repeated advice from her oncologist. She eventually started consistent Tamoxifen in 2013, at which point her cancer showed good control. She also received only 21 of the 25 planned radiation treatments for the 2011 chest wall recurrence.

The court acknowledged that there were reasons for these decisions: her oncologist, Dr. Chouinard, had initially held off on Tamoxifen because of her pre-existing depression and the known risk of depression as a side effect of the medication. But by 2012, her oncologist had made clear that she needed to start it. She understood the advice and declined to follow it. Morissette J. applied an 18% reduction to general damages for failure to mitigate the post-diagnosis consequences of the negligence.

The Damages Award

Non-Pecuniary General Damages

Before the negligence, Mrs. DeBoer had been an active person who ran, biked, played volleyball, and loved her work as an Air Canada flight attendant. She had a marriage and a family. Even with a pre-existing history of mild depression, she was engaged in life. The diagnosis transformed that picture. She endured chemotherapy with severe side effects including hospitalizations, fatigue, and exacerbated depression. She lived with the chronic pain of metastatic bone disease. She underwent multiple surgeries. She was forced to resign from a career of over 30 years in the summer of 2016 because her shoulder metastases made it impossible to close overhead bins or lift heavy items. The dismal prognosis overshadowed her daily life.

General damages were assessed at $275,000 and reduced by 18% for failure to mitigate, producing an award of $225,500.

Income Loss

The parties agreed on a number of parameters: Mrs. DeBoer would have retired at age 63; normal life expectancy of 86; reduced life expectancy of five years from trial; she would have been unable to work for 18 months even with an earlier diagnosis (for mastectomy and cancer treatment), so no income loss claim was advanced for that period. Past income loss from 2010 to trial was agreed at $30,000. Future income loss was agreed at $650,260, consisting of employment income loss from trial to assumed life expectancy ($290,935), employment income loss from assumed life expectancy to assumed retirement at 63 ($140,000), and pension income loss from retirement to normal life expectancy of 86 ($229,325).

Ministry of Health and Family Law Act Claims

The Ministry of Health’s subrogated claims were $40,000 for past care and $60,000 for future care, both allowed.

Family Law Act claims were allowed for the family members. Kenneth DeBoer’s claim was assessed at $50,000 for the loss of his wife’s companionship and care over the years of her illness and during the premature death she faced. Each of the children (Kevin and Krista) was assessed at $15,000. The court noted that Krista had not testified, but saw no reason to treat her differently from her brother Kevin on this basis.

What Deboer v Kolyn Establishes

Principle One: BI-RADS Scoring and What Requires a Rating of 4

The analysis of Dr. Tsin’s breach establishes the combination of factors that, in a diagnostic (not screening) mammography, should elevate a BI-RADS rating to 4 (suspicious). A premenopausal patient under 50 with a palpable lump and dense breasts presenting for a diagnostic study is not the same clinical picture as a routine population screening. Heterogeneous, clustered calcifications in a segmental distribution are not the same as diffuse bilateral uniform calcifications. And where the imaging is insufficient to characterize the distribution of calcifications confidently, because supplementary and magnification views have not been obtained, the answer is not to assign a “probably benign” rating: it is to obtain the additional imaging. A BI-RADS 4 rating triggers a biopsy. A BI-RADS 3 rating does not. The difference in the rating given to Janice DeBoer’s 2009 mammogram was the difference between early diagnosis and nine months of delay.

Principle Two: Discordant Biopsy Findings Must Be Acted Upon

The handling of the February 2010 Trucut biopsy is the most instructive passage in the decision for practising surgeons and their defence counsel alike. A pathology result showing only “benign breast tissue without specific abnormality,” with no microcalcifications, no specific features of fibroadenoma, and an explicit pathologist’s note that clinical and radiographical correlation was required, is not a clean bill of health. It is a signal that the correct tissue may not have been sampled. The blind biopsy (without image guidance) of a small deep lump compounded this concern: a biopsy needle can push a small deep lump away, and without imaging confirmation, the needle’s path cannot be verified.

The obligation when biopsy results are discordant with clinical presentation is not to rationalize the benign result and move on. It is to order further imaging and to biopsy again until concordance is established, until the pathology result actually explains what the clinician sees on physical examination. Dr. Kolyn’s failure at this juncture was fatal to the management of Mrs. DeBoer’s case.

Principle Three: The “Tumour Biology” Defence Must Be Proved, Not Assumed

Deboer v Kolyn is one of the most detailed judicial treatments in Ontario of the “aggressive tumour biology” defence in breast cancer malpractice cases. The defence argument, that the cancer had already spread microscopically before any earlier diagnosis was possible, so the outcome would have been the same, is legitimate in principle but requires affirmative evidentiary support. It cannot be established by inference from histological grade alone or by asserting that recurrence proves pre-existing micrometastasis.

The markers that actually reflect biological aggressiveness (hormone receptor status, HER2neu status, timing and location of metastases, response to treatment) must be examined in their totality. In this case, they were. And they pointed away from the aggressive biology the defence argued. A cancer that is ER+PR+, HER2neu negative, bone-metastatic rather than visceral-organ metastatic, and responsive to both Tamoxifen and radiation is not behaving like the highly aggressive, micrometastatic-at-diagnosis cancer Dr. Fine described. His theory was speculative and the available clinical evidence contradicted it.

Principle Four: The Adverse Inference from Failure to Conduct Available Genetic Testing

The court’s drawing of an adverse inference from the defendants’ failure to conduct Onco-Type DX testing is a principle with broad implications. Where a defendant’s causation theory depends on a proposition (such as the biological aggressiveness of a tumour) that could have been objectively tested using available genetic technology, and the defendant had both the means and the reason to conduct that testing, the failure to do so permits an adverse inference. The inference is not that the testing would have shown the opposite of what the defendant claims; it is that the defendant’s speculative oral opinion is not supported by the objective evidence they could have obtained and chose not to. This principle will be increasingly significant as genetic tumour profiling becomes more routine in oncological practice.

Principle Five: Statistics and Legal Causation in Cancer Cases

The court’s handling of Dr. Fine’s statistical survival-rate analysis confirms a distinction that practitioners must understand: the legal standard of causation on the balance of probabilities is not the same as a fifty percent threshold on a single statistical measure. Where all the evidence in a specific case (the clinical trajectory, the biological markers, the staging progression, the complications, the treatment complications) cumulatively supports a finding that this patient, in this particular situation, would on the balance of probabilities have had a better outcome with proper care, that finding can sustain liability even if no single survival statistic alone reaches fifty percent. The loss of chance doctrine (no liability where the probability of a better outcome was below fifty percent) does not defeat causation where the totality of case-specific evidence establishes causation on a balance of probabilities.

Principle Six: Breast Augmentation as a Complicating Intervening Factor

Deboer v Kolyn presents a specific factual configuration that may arise again: a patient with undiagnosed breast cancer undergoes aesthetic breast surgery in the period of delayed diagnosis, and that surgery directly worsens the management of the cancer when it is eventually identified. Both experts agreed on the mechanical point: the fibrosis and adhesions from augmentation made the mastectomy technically more difficult and increased the likelihood of positive margins. Dr. Potvin extended the analysis further: the scarring reduced the effectiveness of chemotherapy by compromising the blood supply to the tumour bed. A failure to diagnose that enables an intervening aesthetic procedure to complicate the cancer’s management is part of the chain of harm attributable to the original negligence.

Principle Seven: Failure to Mitigate and the Depression Complication

The 18% reduction for failure to mitigate is a measured response to a genuinely complex situation. Mrs. DeBoer’s pre-existing depression was a real factor; her oncologist had specifically held off on Tamoxifen because it risked aggravating her depression, a recognized side effect. But by 2012, she understood the importance of the medication and chose not to take it. The court’s approach, recognizing the complexity of post-diagnosis treatment decisions while still applying a failure-to-mitigate reduction, provides a model for similar situations. Depression and anxiety arising in the context of a cancer diagnosis may explain some non-compliance, but they do not eliminate the plaintiff’s obligation to take reasonable steps to mitigate harm. Where non-compliance is deliberate and informed, a reduction is appropriate.

Deboer v Kolyn in the Cancer Diagnosis Series

This case is cited in the Cancer Diagnosis Claims Guide and the General Medical Malpractice Guide in this series. It is a comprehensive trial-level decision on missed breast cancer involving two defendants (a radiologist and a surgeon) at sequential points in the diagnosis pathway. It illustrates how negligence at an early diagnostic step (the radiologist’s BI-RADS rating) can cascade through subsequent clinical decisions (the surgeon’s reliance on the imaging report, the blind biopsy, the failure to act on discordant findings) to produce a harm far greater than any single step alone would have caused.

It pairs with the discussion of causation principles in the series article on Benhaim v St-Germain and on Snell v Farrell, and with the cancer-specific analysis in the Cancer Diagnosis Claims Guide. For the breast-specific standard of care analysis, the discussion of BI-RADS ratings, the “triple assessment” standard for breast lumps (clinical examination, imaging, and biopsy), and the obligation to act on discordant findings are developed in the practical guidance sections of that guide.

Quick Reference: Deboer v Kolyn

Case Details

• Deboer v Dr. D. M. Kolyn, 2016 ONSC 7108 (CanLII) — https://canlii.ca/t/gwll8 | File: 6805/12 | Morissette J. | Heard September–October 2016 (13 days) | Released December 23, 2016
• Outcome: Plaintiffs successful on liability and causation; 18% failure-to-mitigate reduction applied to general damages

The Key Parties

• Plaintiff: Janice Nicole Deboer, age 45 at time of events; Air Canada flight attendant (30+ years); married with two children (Kevin and Krista)
• Defendant 1: Dr. D. M. Kolyn, general surgeon, Cambridge Memorial Hospital
• Defendant 2: Dr. T. Tsin — radiologist
• Family plaintiffs: Kenneth Anthony Deboer (husband), Kevin Daniel Deboer and Krista Lee Deboer (children)

The Timeline

• Mid-2009 (age 45): Right breast lump detected at 5 o’clock position
• July 22, 2009: Mammogram and ultrasound conducted; dense breasts; cluster of coarse heterogeneous microcalcifications noted
• August 1, 2009: Dr. Tsin’s report: BI-RADS 3 (“probably benign”); BREACH; should have been BI-RADS 4; no supplemental or magnification views ordered; false annotation that “coned mag bilateral view” had been done
• December 21, 2009: Dr. Kolyn appointment; lump described as “hard and lumpy” and “different than past fibroadenomas”; plans excision for February 2010; no further imaging ordered
• February 16, 2010: New 7 o’clock lump; Dr. Kolyn performs blind Trucut biopsy without image guidance: BREACH; pathology returns benign with discordant note; Dr. Kolyn does not act on discordant findings: BREACH; 5 o’clock lump not investigated: BREACH
• May 3, 2010: Breast augmentation surgery by Dr. Kaila (plastic surgeon); both lumps removed; pathology: invasive ductal carcinoma
• June 2010: Lymph node metastasis confirmed; mastectomy performed; complicated by augmentation scar tissue; positive margins
• July 2011: Local chest wall recurrence; radiation
• November 2013: Bone metastases
• 2016 (time of trial): Stage IV incurable metastatic breast cancer; Mrs. DeBoer resigned from Air Canada

The Breaches

• Dr. Tsin: BI-RADS 3 instead of BI-RADS 4; failure to request supplemental cranial caudal images and magnification views; inaccurate annotation of imaging performed
• Dr. Kolyn: Blind Trucut biopsy without real-time ultrasound image guidance; failure to act on discordant pathology findings (benign result plus explicit correlation note); failure to investigate 5 o’clock lump with imaging or biopsy; failure to order further imaging before breast augmentation surgery

Causation

• Cancer was Stage I in summer 2009: diagnosable, treatable, and curable
• By May 2010 diagnosis: Stage II, multifocal, lymph node positive
• Breast augmentation surgery complicated mastectomy (scar tissue, positive margins) and reduced chemotherapy effectiveness
• Tumour biology was NOT aggressively high-risk: ER+PR+ and HER2neu negative; bone metastases (not visceral); responsive to Tamoxifen and radiation; alive 7 years post-diagnosis
• Adverse inference drawn from defendants’ failure to conduct Onco-Type DX genetic testing
• But for negligence: Mrs. DeBoer would not have bone metastases; would still be working; would not die prematurely

Damages

• Non-pecuniary general damages: $275,000 → reduced by 18% for failure to mitigate (not taking Tamoxifen as directed; incomplete radiation) = $225,500
• Past income loss (2010–trial): $30,000
• Future income loss: $650,260 (employment and pension losses combined)
• Ministry of Health subrogated: $40,000 past care + $60,000 future care
• Mr. DeBoer Family Law Act: $50,000
• Kevin DeBoer Family Law Act: $15,000
• Krista Lee Deboer Family Law Act: $15,000

Key Legal Principles

• BI-RADS 4 is required (not BI-RADS 3) where a patient is premenopausal, under 50, has a palpable lump, dense breasts, and heterogeneous calcifications in a segmental distribution on diagnostic (not screening) mammography
• Discordant biopsy findings (benign result inconsistent with clinical presentation, accompanied by a pathologist’s explicit note requiring clinical/radiographical correlation) must be actively investigated; a benign blind biopsy result is not a clean bill of health
• The “tumour biology” defence requires affirmative evidentiary support through specific biological markers; histological grade alone is insufficient; clinical trajectory, hormone receptor status, HER2neu status, and metastatic pattern must be assessed in totality
• Adverse inference can be drawn from a defendant’s failure to conduct available genetic testing (Onco-Type DX) where the defendant’s theory depends on the result of such testing and it was within their power to obtain it
• Statistical survival differences do not control legal causation where the totality of case-specific evidence establishes causation on the balance of probabilities
• Intervening aesthetic surgery during a period of delayed cancer diagnosis, which complicates subsequent cancer management, is part of the chain of harm attributable to the original negligence
• Failure to take prescribed Tamoxifen (when not contraindicated) and incomplete radiation therapy constitute failure to mitigate; an 18% reduction was applied to general damages
• Family Law Act claims for loss of guidance, care and companionship are compensable for a spouse and children in cancer malpractice cases; a child who did not testify can still have their claim assessed (no reason to treat children differently from each other)

Related Cases in This Series

• Snell v Farrell, 1990 CanLII 70 (SCC) — https://canlii.ca/t/1fstw — the “but for” test and the robust and pragmatic approach to causation; article in this series
• Benhaim v St-Germain, 2016 SCC 48 (CanLII) — adverse inference and the “but for” test in missed cancer diagnosis; article in this series
• Clements v Clements, 2012 SCC 32 (CanLII) — https://canlii.ca/t/frvld — material contribution to risk; article in this series
• Ter Neuzen v Korn, [1995] 3 SCR 674 — https://canlii.ca/t/1frhk — professional standard of care at the time of the events; article in this series
• Hopp v Lepp / Reibl v Hughes — informed consent and disclosure obligations; articles in this series