Abstract:

Primary apocrine adenocarcinoma (AA) is a rare cutaneous malignancy with only approximately 50 cases documented worldwide. We present an 81-year-old Hispanic female with a 5 x 5 cm exophytic, slightly necrotic mass adherent to the upper chest wall. The lesion had slowly been enlarging over the previous year. Shave biopsy revealed nests and cords of atypical cells within the dermis some forming glands with apocrine snouts and decapitation secretion. The tumor was predominantly apocrine with a minor cribiform pattern. Also multiple connections to the epidermis with focal epidermotropic spread were noted. Immunohistochemical (IHC) stains were strongly positive for CK-7, Ber-EP4, and GATA-3. Additionally, P63 was focally positive. While connections to the epidermis and focal areas of p63 positivity favored a primary apocrine adenocarcinoma of the skin, breast carcinoma could not be completely excluded. Mammogram was then performed without evidence of malignancy and the lesion of concern was discrete from the breast tissue. CT Chest/Abdomen/Pelvis was remarkable for an 8mm lymph node (LN) within the left axilla but sentinel LN biopsy was negative. Our case serves as a reminder of primary AA as a rare cutaneous malignancy with metastatic potential. Additionally, we aim to emphasize that a diagnosis of primary AA cannot be rendered without ruling out metastatic breast carcinoma due to significant diagnostic overlap. Positive staining with CK-7, mammaglobin, and GATA-3 is suggestive of breast adenocarcinoma while staining with GCDFP-15 and p63 is strongly suggestive of primary cutaneous AA. In conclusion, the histologic criteria for diagnosis of primary cutaneous AA are poorly defined due to the rarity of this disease and further research is warranted.

Financial Disclosure:
No current or relevant financial relationships exist.

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Anna Catinis