Adequate Core Biopsy Samples from Stereotactic Biopsies Needed for Today’s Breast Pathology
Background: There is a paradigm shift in breast biopsy philosophy. In the past radiologists and clinicians used to collect as little tissue as possible for pathologists to render a diagnosis on conventional histologic H&E sections. Precision medicine has changed this philosophy in such a way that more optimal core biopsy specimens are now required to provide more data for personalizing the therapy.
Methods: Two cases are presented in this study to illustrate the importance of adequate stereotactic breast biopsy samples. In each case digital mammography revealed grouped heterogeneous calcifications in a postmenopausal woman. A core biopsy was performed using stereotactic 8 gauge vacuum-assisted biopsy equipment. Cores were collected in touch-free collection chambers; and the specimen radiograph confirmed the targeted calcifications. Core biopsy samples were completely submitted for paraffin embedding into two cassettes. Cores bearing microcalcifications on specimen radiography were submitted for paraffin embedding in one cassette; the remainder cores were submitted in another cassette.
Results: In one case, microscopic examination revealed ductal carcinoma in situ grade 1 (DCIS grade 1) measuring more than 2 mm in linear extent involving multiple ducts on a single core with microcalcifications. In another case, microscopic examination revealed ductal carcinoma in situ grade 2 with microcalcifications (DCIS grade 2) mixed with moderately-differentiated invasive ductal carcinoma. P63 and calponin immunostains delineated the size of invasive carcinoma (2.5 mm, pT1a) and DCIS (> 6 mm) on a single core.
Conclusions: An important diagnostic criterion for classification of low nuclear grade atypical ductal proliferations is the size/extent of the lesion. Larger, intact, unfragmented biopsy samples enable atypical ductal hyperplasia (ADH) versus DCIS grade 1 distinction possible as seen in first case. The distinction between these two diagnoses often mean a difference in how the patient proceeds with treatment, reinforcing the need to acquire high quality and quantity of biopsy samples. Adequate, unfragmented samples provide high quality tissue for accurate diagnosis and further ancillary studies as seen in the second case.
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Histopathologic examination of adequate, minimallyinvasive breast core biopsy samples corresponding to an abnormal radiological finding is the standard of care prior to any therapeutic intervention or mammographic surveillance decision.
Excision of breast (breast conserving surgery, mastectomy) without prior minimally-invasive core biopsy diagnosis is almost an obsolete clinical practice.
It is imperative to have a quantitatively and qualitatively adequate sample in order for a pathologist to formulate an ironclad diagnosis. Majority of patients with imaging abnormality who have undergone minimally-invasive breast core biopsy with benign diagnosis are spared further excision and excision-related complications. Many of these patients are managed with radiological surveillance only.
Quality of the individual tissue sample should be optimal to provide a confident radiological-pathological correlation. Undersampling of clinically significant lesions (invasive / in situ carcinoma, atypical ductal hyperplasia, complex radial scars, papillary neoplasms with or without atypia) and fragmented inadequate samples could easily lead to a false negative “benign breast tissue” histologic diagnosis. According to a recent article published in the Journal of Clinical Oncology, insufficient cancer tissue for biomarker testing occurred across 4 out of 5 cancer types reported on. The majority of tissue samples in which insufficient tissue was present were acquired through core biopsies (67% of all cases) or FNAs (22% of all cases).1
Quantity of the tissue of interest should be optimal to perform ancillary diagnostic studies (P63, calponin, CK903, E-cadherin, CK5/6, CK 7, MNF 116, S100, reticulin stains etc.) or prognostic predictive markers (ER, PR, AR, Ki67,