Primary Cutaneous Apocrine Carcinoma: Diagnostic and Management Difficulties of an Uncommon Neoplasm

Primary cutaneous apocrine carcinoma (PCAC) is a rare adnexal neoplasm. Due to its clinical presentation, it can mimic other tumors, especially metastasis. We present a case of primary apocrine carcinoma of the axilla mimicking breast carcinoma metastasis in a 54-year-old woman. The patient presented with a painless, lobed, and erythematous nodule in the left axilla of one year duration. We suspected an adnexal neoplasm but also considered metastasis from breast carcinoma. Histological examination revealed apocrine proliferation. Immunohistochemistry stains of tumor cells were positive for AE1/AE3, and negative for CK7, CK20, p63 and GATA3. Radiological explorations did not reveal any signs of malignancy. Considering all these features, the conclusive diagnosis was primary cutaneous apocrine carcinoma. Treatment was wide excision without adjuvant therapy, and no recurrence was noted. Due to the rarity of this carcinoma, its various clinical presentations, and histological overlaps with breast cancer metastasis, making the diagnosis may be challenging. A comprehensive evaluation of all findings is necessary to rule out other tumors. There is any consensus on the management strategy. The standard treatment is surgical excision, but adjuvant therapies such as radiotherapy or chemotherapy can be proposed in advanced stage disease.