ABSTRACT
Carcinoma of the breast with apocrine differentiation also known as apocrine adenocarcinomas is special histological subtypes comprising approximately 1% of breast cancers. They are estrogen receptor/progesterone receptor-negative and androgen receptor-positive tumors having more than 90% population of tumor cells with apocrine morphology. We present a 49-year-old woman with a breast lump in the right upper outer quadrant clinically and radiologically diagnosed as malignancy and histologically proven as apocrine adenocarcinoma of the breast owing to the morphology comprising tumor cells having abundant granular cytoplasm, central to the eccentric nucleus and prominent nucleoli. On immunohistochemistry, it was a triple-negative tumor with AR positivity. As apocrine adenocarcinoma of the breast has an uncertain prognosis, variable HER2/neu overexpression, debatable responses to neoadjuvant therapy, and probable response to androgen therapy, the onus of diagnosing and reporting these tumors accurately lies with the pathologist. Moreover, as the presentation of these tumors is similar to invasive breast carcinoma, no special type but with potentially different and useful theranostic markers, an emphasis on specifying this histological subtype is becoming increasingly essential.
