Tubulopapillary Apocrine Carcinoma Arising in the Knee: A Case Report. (21st September 2018) - Patel, Krutika
Abstract: Apocrine carcinoma is an extremely rare cutaneous adnexal malignancy. Distinctive clinical features, sex preponderance, and clinical course are not clearly defined. The most common site is the axilla, although it is also occasionally found in the anogenital area, nipple, and neck. Although controversy exists regarding its treatment, use of multimodal therapy with wide local excision and adjuvant radiotherapy has shown beneficial outcomes. We present here a case of a 39-year-old female who presented with a 0.6-cm solid-appearing fixed nodular lesion on the knee, with crusting of the overlying skin. The cut surface had a fibrous appearance. Histopathological examination of the resected specimen showed a poorly circumscribed adenocarcinoma forming tubular and cystic lumina in a complex papillary arrangement. Some glandular lumina were cystically dilated and contained eosinophilic necrotic material. Variable nuclear pleomorphism and mitotic activity were noted. An infiltrative growth pattern into the surrounding adnexal structures and nerves was observed. There was no evidence of coexisting accessory mammary glands or any underlying occult malignancy. Based on these histomorphological findings, the diagnosis of apocrine carcinoma was made. Apocrine carcinoma of the cutaneous appendages is the malignant counterpart of tubular apocrine adenoma and hidradenoma papilliferum, with some reports having explored the possible association between apocrine hyperplasia, apocrine adenoma, and carcinoma. The presence of decapitation secretion or a benign apocrine component on the periphery distinguishes it from the common differential diagnoses, which include metastatic breast carcinoma and eccrine ductal carcinoma. Metastases to locoregional lymph nodes and distant viscera have been reported in 40% of cases. Our case exhibits multiple unique characteristics: a rare tumor, in an unusual location, diagnosed on a biopsy specimen. This case highlights the need for a definitive diagnosis in such rare entities to establish standard management guidelines.