Primary cutaneous adenoid cystic carcinoma: a clinicopathologic and immunohistochemical study of 27 cases.

This study examines clinical and pathologic features of primary cutaneous adenoid cystic carcinoma (ACC), with emphasis on biological behavior of these tumors. A total of 27 cases of primary cutaneous ACC with detailed follow-up information were evaluated. Clinically, these were solitary, slow-growing lesions, half of which were in the head and neck area. The median age was 62 years with a male predilection. Surgical excision was the treatment of choice. Histologically, the lesions were similar to those seen in the salivary glands. Tumors were classified as grade 1 (17), grade 2 (3), and grade 3 (7). The mitotic count was generally low (mean=1.9/mm), except in 2 high-grade tumors (>10 mitotic figures/mm). Sixteen cases showed perineural invasion. Immunohistochemically, cytokeratin positivity was noted in 13/13 cases, and CD117 was observed in 10/10 cases, with luminal/cytoplasmic staining for epithelial membrane antigen (14/16) and at least focal luminal expression for carcinoembryonic antigen (11/16), smooth muscle actin (10/13), and S100 staining (9/13). Eighteen cases had follow-up data (median 54 mo), 9 of which had local recurrences (50%). Three cases showed metastatic disease. No statistical difference was noted between tumor grade and local recurrence (P=0.77). Primary cutaneous ACC is a distinct entity with a more indolent behavior compared with its salivary counterpart. The cutaneous lesions tend to recur locally but have a low metastatic potential.