Breast hamartoma: reassessment of an under-recognised breast lesion.

AIMS: Breast hamartomas are an under-recognised lesion because they lack a distinctive microscopic appearance. Microscopic diagnosis can often conclude 'no significant lesion' or 'normal breast tissue', leading to repeated biopsies and diagnostic delay. We describe the histological, immunohistochemical and radiological features of breast hamartomas with the aim of identifying specific signs to facilitate their diagnosis and to differentiate them from normal breast and fibroepithelial lesions. METHODS AND RESULTS: Forty-seven breast hamartomas were reassessed (histological diagnosis and imaging features). An immunohistochemical study [oestrogen receptor (ER), progesterone receptor (PR), CD34, high-mobility group A2 (HMGA2)] was performed. On breast imaging, hamartomas most often presented as probably benign solid masses with circumscribed margins and variable densities. Histologically, breast hamartomas resembled normal breast, although their stromal component was predominant, separating randomly scattered epithelial elements with areas of pure collagenous stroma. Pseudoangiomatous stromal hyperplasia (PASH) was present in 93.6% of cases and CD34 antibody highlighted intralobular, perilobular and interlobular distribution of CD34-positive fibroblasts. By comparison, CD34 was mainly expressed in the intralobular normal breast tissue stroma. Hamartoma stromal cells expressed HMGA2, ER and PR in 79%, 66% and 76.3% of our cases, respectively, compared to 7.7%, 23% and 19% in normal breast tissue, respectively (P < 0.0001; P = 0.0005; P < 0.0001). CONCLUSIONS: After ascertaining that core needle biopsy is effectively intralesional, breast hamartomas can be diagnosed with confidence by taking into account the presence of stromal changes, PASH, interlobular distribution of CD34-positive fibroblasts, HMGA2 and hormonal receptor stromal expression.

Impact of Obtaining a Digital Breast Tomosynthesis (DBT) Spot Compression View on Assessment of Equivocal DBT Findings.

BACKGROUND. A recently introduced digital breast tomosynthesis (DBT) device allows acquisition of DBT spot compression views with a small paddle during DBT acquisition. OBJECTIVE. The purpose of this study was to evaluate the impact on diagnostic performance of obtaining a DBT spot compression view for assessment of equivocal DBT findings. METHODS. This retrospective study included 102 women (mean age, 60 years) in whom a DBT spot compression view was obtained to characterize an equivocal finding on DBT at the performing radiologist's discretion. The DBT examinations were performed from December 14, 2018, to December 18, 2019. Two fellowship-trained breast radiologists and one breast imaging fellow, who were aware of the location of the equivocal lesions, independently reviewed the examinations. Readers first assigned a BI-RADS category using standard DBT views and then immediately assigned a category using the DBT spot compression view. BI-RADS categories 2 and 3 were considered negative, and categories 4A and greater were considered positive. Histology and at least 1 year of imaging follow-up served as the reference standard. Intrareader agreement for one reader and interreader agreement among all readers were evaluated with kappa coefficients. Diagnostic performance was compared between DBT with and DBT without spot compression views by use of McNemar tests. RESULTS. Intrareader agreement increased from 0.43 to 0.72, and interreader agreement increased from 0.21 to 0.45 on the basis of kappa coefficients for DBT without and with spot compression views. Eighteen cancers were present. Compared with standard DBT views, DBT spot compression views yielded significantly increased accuracy for all three readers (75% vs 90%, 74% vs 94%, 72% vs 94%); significantly increased specificity for all three readers (69% vs 90%, 75% vs 94%, 68% vs 93%); and significantly increased sensitivity for one reader (67% vs 94%) without significant change in sensitivity for the two other readers (89% vs 100%, 100% vs 89%). Radiation dose was 1.97 mGy for the DBT spot compression view versus 1.78-1.81 mGy for standard DBT craniocaudal and medio-lateral oblique views. CONCLUSION. Use of the DBT spot compression view increased intrareader agreement, interreader agreement, and diagnostic accuracy (primarily owing to improved specificity); the supplemental dose for the spot compression view was slightly higher than that for a standard DBT view. CLINICAL IMPACT. DBT spot compression may help characterize equivocal DBT findings, reducing further workup for benign findings.