Primary adenoid cystic carcinoma of the skin metastatic to the lymph nodes: immunohistochemical study of a new case and literature review.

Primary cutaneous adenoid cystic carcinoma (PCACC) is a rare adnexal skin tumor first described in 1975, of which merely 62 cases have so far been studied in detail and reported in the English literature. PCACC is usually regarded as apocrine in origin/differentiation, but its precise histogenesis is still not well known. PCACC has in most cases a rather indolent course but can produce local recurrences and, more rarely, regional (lymph node) and distant (pulmonary) metastases. We report herein a Greek woman with a long-standing PCACC that grew slowly over several years and produced metastasis in the regional lymph nodes, highlighting the potentially aggressive course of this tumor. The primary and metastatic tumors were studied immunohistochemically and proved to express several (sweat gland-related) antigens (such as keratin 7, epithelial membrane antigen, CD10, and CD117) but neither hormonal receptors nor p63 or Gross Cystic disease Fluid Protein 15. The salient clinicopathologic features of this rare cutaneous adnexal tumor are reviewed.