A 33-year-old woman with a prior history significant for a breast carcinoma nine years ago, presented with a palpable lump in her breast. Imaging showed a 0.7 x 0.6 x 0.3 cm oval hypoechoic mass with internal vascularity at 6 o’clock position, 4-5 cm away from the nipple, corresponding to the palpable area of concern.
The correct answer is ...
Secretory carcinoma of the breast.
Secretory carcinomas of the breast are very rare. However, they are the most common primary pediatric breast malignancy. On histology, they show circumscribed margins, solid nests, cysts and gland formation with PAS+ intraluminal secretions. Tumor cells with abundant vacuolated or granular cytoplasm and low nuclear grade are seen. They are generally negative for estrogen receptor, progesterone receptor, and HER2 (triple negative). Most tumors have translocation yielding ETV6-NTRK3 fusion gene and are associated with a favorable prognosis in younger patients.
Apocrine carcinomas of the breast are rare tumors and comprise of up to 1% of all breast carcinomas. Tumor cells have distinct cell margins, abundant acidophilic cytoplasm with eosinophilic granules, central to eccentric vesicular nuclei with prominent nucleoli. They may also have glandular features with apocrine snouts. Apocrine carcinomas of the breast are typically negative for estrogen and progesterone receptors and can show expression for androgen receptor. HER2 positivity may be seen in one-third of apocrine carcinomas.
Primary acinic cell carcinomas are exceedingly rare in the breast and only a handful of cases have been reported in the medical literature. They are morphologically identical to their salivary gland counterparts and have a serous differentiation.
These carcinomas show diffuse infiltrative growth patterns of small glandular structures and are composed of cells with a coarse granular or clear cytoplasm resembling acinar cells of the salivary glands or Paneth cells. Although similar in some respects to secretory carcinoma, they lack its characteristic ETV6 gene rearrangement. Acinic cell carcinomas are usually triple negative and show expression for amylase and the granules are PAS positive diastase resistant.
Cystic hypersecretory hyperplasia can present as a palpable mass or occasionally can be asymptomatic. It is a benign lesion with good prognosis when not associated with atypia or carcinoma. Microscopically, cystically dilated ducts of various sizes with colloid-like material can be seen. Ducts are lined by flat, orderly, columnar epithelial cells with eosinophilic cytoplasm. The nuclei are bland, round or oval. They can be associated with pregnancy-like (pseudolactational) changes. Wide excision of the lesion is the recommended treatment for this lesion.
Muhammad Ahmad, M.B.B.S.
Fellow, Multidisciplinary Breast Pathology
Malvika Solanki, M.B.B.S., Ph.D.
Senior Associate Consultant, Anatomic Pathology
Assistant Professor of Laboratory Medicine and Pathology
Mayo Clinic College of Medicine and Science