Primary Cutaneous Adenoid Cystic Carcinoma of the Leg

Summary: Adenoid cystic carcinoma (ACC) is a rare tumor that arises at sites including the salivary gland, breast and skin. Cutaneous metastases secondary to breast ACC is an extremely rare occurrence. We describe a 49-year-old woman presenting with a palpable left breast mass. Biopsy confirmed the diagnosis of ACC, high-grade (>30% solid areas). She underwent lumpectomy and chemotherapy with no response. Sixteen months after initial breast ACC diagnosis, she developed a new, enlarging skin lesion on her left shoulder. Microscopic examination showed a relatively well-circumscribed lesion with an infiltrative border involving the dermis and subcutis. The tumor was comprised of islands, trabecular, and cribriform pattern with a solid-basaloid appearance. It also showed expression of MYB1 and CD117. Overall findings are consistent with metastatic ACC. Although ACC generally is an indolent disease and is managed with complete excision, it has been reported that the prognosis of ACC of the breast with solid pattern is associated with an aggressive clinical course and has the potential to metastasize, as shown in the case here reported.