College of American Pathologists
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What went wrong? Learn to confirm—lessons from a core needle case

May 2002
Susan Tannenbaum, MD

Marva West Tan, RN, ARM

Following is an analysis of a closed breast pathology claim managed by The St. Paul and MMICompanies Inc., St. Paul, Minn., the CAP-endorsed professional liability insurer. Some facts may have been changed in the following case to protect confidentiality. Analyses of two other breast pathology claims appeared in the April issue.

Allegation: Failure to properly diagnose core needle biopsy, failure to abide by the proper pathological standard of care, misdiagnosis of invasive ductal carcinoma with unnecessary right breast mastectomy, axilla and sentinel lymph node biopsy and removal, lymphedema of right arm, and pain and suffering.

Defendants: Pathologist, pathology group practice, surgeon, and surgical group practice.

Facts of case: Mrs. B, a 55-year-old woman, was seen by her family physician on April 27, 1999. The physician discovered a small lump in her right breast and referred her for a mammogram and ultrasonogram. The family history was positive for breast cancer in the patient’s mother.

Following is the sequence of events:

  • April 27, 1999. A radiologist completed the mammogram and ultrasonogram and reported to the family physician the presence of a suspicious lesion in the right breast.
  • April 27, 1999. The family physician referred the patient to a general surgeon who performed a right core needle biopsy in the office. At the time the surgeon performed the core needle biopsy, she was participating in a university-sponsored sentinel node certification program, which required that the surgeon complete 30 mastectomies with sentinel node level 1 and level 2 lymph node excisions following university protocol.
  • April 29, 1999. The patient alleges that prior to receiving the pathology report of the core needle biopsy, the surgeon told her she had breast cancer and scheduled her for a mastectomy and axillary node removal. The patient further alleges that the surgeon did not discuss other treatment options with her but did explain possible breast reconstruction postmastectomy. The surgeon also requested that the patient participate in the sentinel node study, with the understanding that the findings might help future cancer patients. The patient apparently agreed to participate and signed the appropriate study consent forms.
  • April 29, 1999. The pathologist issued a report on the right breast core needle biopsies with the diagnosis of invasive ductal carcinoma with apocrine features.
  • May 3, 1999. The patient had sentinel node identification, with right breast modified radical mastectomy and lymph node excisions.
  • May 12, 1999. Outside consultant Pathologist No. 1 received a request to provide a second opinion.
  • May 17, 1999. Outside consultant Pathologist No. 1 issued a report on the case: breast, right, mastectomy-adenomyoepithelioma.
  • May 21, 1999. The pathologist issued a report on the case: right breast, modified right mastectomy-adenomyoepithelioma, margins negative for tumor; background breast with proliferative fibrocystic changes (moderate duct hyperplasia, sclerosing adenosis, and fibrosis); skin and nipple-negative for malignancy; 21 lymph nodes-negative for malignancy; first, second, and third sentinel lymph nodes-negative for malignancy.
  • June 29, 1999. Outside consultant Pathologist No. 2 issued the following report after the patient’s discharge: right breast, core biopsy-atypical papillary proliferation with apocrine differentiation; right breast, mastectomy specimen-intraductal carcinoma, apocrine cell type with focal sebaceous and squamous metaplasia arising in a papilloma; fibrocystic change with apocrine metaplasia; duct ectasia (chronic periductal mastitis); microcalcifications.

Expert pathology consultant No. 2 indicated in the report that since the original core biopsy revealed only a small sample of the neoplasm, it could best be described as an atypical papillary proliferation but could not be definitively classified and that he would have recommended complete excision of the lesion with clinical followup.

Postoperatively, the patient had swelling in her right arm, visited the emergency room to have fluid drained, and used a lymphedema pump at home. At a postoperative office visit (date unclear), the surgeon told the patient that she never had cancer and a laboratory error had occurred.

Legal action: Approximately one-and-a-half years after the mastectomy, the patient filed a suit naming the pathologist, pathology group practice, surgeon, and surgical group practice as defendants. The defendant’s expert pathology witness interpreted the core needle biopsy slides as complex papillary lesion but described in the mastectomy specimen an intraductal carcinoma, apocrine type, arising in a papilloma. The plaintiff’s expert pathology witness noted that the core samples, although rather incomplete, showed the characteristics of a benign lesion. The plaintiff’s position was that no final diagnosis should have been made based on the core sample alone and that additional tissue samples or a frozen section were the standard of care. The case was eventually settled in the mid ranges,* with approximately half the settlement allocated to the pathologist and half to the surgeon.

Clinical issues and standard of care: This claim might have been avoided if the surgeon had adhered more closely to standard clinical guidelines for evaluating and treating a breast lump. The surgeon who read the pathologist’s core biopsy report overzealously performed a mastectomy when the findings, including the pathologist’s report of infiltrating duct carcinoma, would have led a more conservative surgeon to a lumpectomy. The clinical history indicates the plaintiff’s family physician discovered a "small lump" in her right breast on April 27, 1999. An intraoperative frozen section was not performed, and although the three sentinel nodes showed no tumor, as clearly stated in the pathology report, the surgeon removed 21 additional lymph nodes.

The pathology report of the mastectomy specimen does not reveal the exact size of the mass; however, the gross description of "portion tumor right breast" describes a "2.5- by 1.3- by 1.1-cm portion of tissue with an indurated gray cut surface." It must be deduced that the surgeon did not have an exact measurement of the tumor, whatever its classification, or a frozen section diagnosis. The surgeon performed the mastectomy without this information.

Further compounding the complexity of this case, the lesion was diagnosed by the first of the defense’s expert pathologists as an adenomyoepithelioma, a very uncommon lesion that has components that may mimic and be confused with tubular and ductal adenomas, sclerosing papillomas, and, with limited material from a core needle biopsy, presumably infiltrating carcinoma.

The second expert pathologist for the defense, who was part of a reputable and world-class pathology group, found in the mastectomy specimen a malignant component within the otherwise benign lesion, calling it intraductal carcinoma, apocrine cell type, with focal sebaceous and squamous metaplasia arising in a papilloma. This consultant group stated in its letter that review of the core biopsy material showed an atypical papillary proliferation, not definitely classifiable, and that the group would have recommended complete excision with clinical followup. The group considered the diagnosis of adenomyoepithelioma but did not classify the lesion as such due to lack of demonstration by the myoepithelial cells of solid, confluent areas of hyperplastic growth.

The first expert consultant reported S-100 and smooth muscle actin positivity, while the second expert pathologist did not perform these immunoperoxidase stains, citing lack of sufficient myoepithelial overgrowth to warrant pursuing the diagnosis of adenomyoepithelioma.

The plaintiff’s expert consultant pathologist gave yet another opinion. He called the lesion an encysted adenotic papilloma, a benign process, yet disagreed with the diagnosis of adenomyoepithelioma. The defense stressed the differing opinions among the experts, but the fact remained that only the defendant pathologist issued a diagnosis of invasive carcinoma.

Adenomyoepitheliomas usually present as solitary lesions that could be confused clinically with carcinoma. There occasionally are microscopic marginal irregularities with extension into breast tissue and an array of growth patterns, including metaplasias and tubule and papillary formations. These can be confused with tubular and ductal adenomas and sclerosing papillomas but differ in the presence of prominent and hyperplastic myoepithelial cells, which may compress and obliterate the tubular lumens. S-100 protein (or actin) and cytokeratin stains are complementary, alternately revealing the myoepithelial and epithelial components. Tubule formation might lead to an erroneous impression of cancer, especially when a core biopsy does not reveal the entire lesion or when the myoepithelial component is not represented.

Tavassoli’s latest edition of Pathology of the Breast reports only 27 cases of adenomyoepithelioma in the Armed Forces Institute of Pathology series.1

In a core biopsy, a clue to the diagnosis of adenomyoepithelioma is finding vacuolated myoepithelial cells, which would not be found in a carcinoma.2

Regardless of whether the lesion represented an adenomyoepithelioma, in situ carcinoma, or complex papillary lesion, performing a mastectomy without documentation by intraoperative frozen section or measurement of the entire mass was regarded as excessive by all the expert witnesses.

Pathologists are at the mercy of overzealous surgeons in some cases—no matter what pathologists say in a report, clinicians can do as they please. Pathologists, therefore, must practice defensively, using terminology such as "suspicious for malignancy, suggest excisional biopsy." While the pathologist could not know the surgeon would perform a mastectomy based on the core biopsy diagnosis, he or she would have been well advised to perform a confirmatory frozen section at the time of surgery. If the surgeon had performed a lumpectomy rather than mastectomy, the patient may have sued on the basis of inaccurate diagnosis, even though a benign diagnosis would have resulted in the same procedure. But the settlement might have been lower in such a case, and the ordeal probably would have been less traumatic for the pathologist.

Informed consent: While lack of informed consent was not a separate allegation, the plaintiff’s deposition indicated that she was dissatisfied with two aspects of the informed consent process. First was that, given the preoperative diagnosis of breast cancer, she was not offered any treatment options other than mastectomy. Second was that the possibility of a postoperative complication of lymphedema was never discussed with her. Another possible consent issue that the client did not raise was that the sentinel node biopsy study protocol required more extensive node dissection than the patient otherwise may have required, even if she had breast cancer. Research study consent forms typically are complex and should be completely and carefully explained to the patient. Some states have specific requirements for discussing treatment options for breast cancer with patients. Nonetheless, informed consent should include a discussion of risks and benefits of treatment alternatives, as well as the risks of forgoing treatment.

Patient with unanticipated outcomes: The surgeon apparently had a frank discussion with the plaintiff regarding the diagnostic error in her case. He attempted to emphasize the positive news that the patient had never had cancer. It is not clear if the patient received any formal counseling following the news of her unanticipated outcome.

As we become experienced at disclosing medical errors, physicians’ use of the best documented approaches for conveying bad news hopefully will help reduce patients’ anger and grief and thus lessen the frequency and severity of malpractice claims.3

1.  Tavassoli F. Pathology of the Breast. 2nd ed. New York, NY: McGraw Hill Health Professions Division; 1999:772.

2.  Rosen P. Breast Pathology Diagnosis by Needle Core Biopsy. Philadelphia, Pa.: Lippincott Williams & Wilkins; 1999: 45.

3.  Frankel R. Challenges and opportunities in delivering bad news. Physicians Quarterly. St. Paul, Minn.: The St. Paul; 2000; 25(3):1-6.

Dr. Tannenbaum is a pathologist at Quest Diagnostics Inc., Teterboro, NJ, and chair of the CAP Insurance Committee. Tan is senior communicator, health care risk services, The St. Paul. The authors would like to thank Helen Feiner, MD, a pathologist specializing in breast pathology, for her expert review of this article.