Pigmented adenoid cystic carcinoma of the ear skin arising from the epidermis: a case report with immunohistochemical studies.

Adenoid cystic carcinoma (ACC) in the skin is very rare; only about 60 cases have been reported. Herein presented is a case of pigmented ACC arising from epidermis of the ear skin. An 85-year-old man presented black tumor of the right ear. Dermatologists' diagnosis was basal cell carcinoma (BCC). Large biopsy was obtained. The biopsy showed proliferation of atypical basaloid cells arranged in a cribriform pattern. The tumor cells were continuous with epidermis, as if it arose from the epidermis. Focal areas show melanin deposition in the tumor cells. Mucin stains showed that the tumor cells and tubular lumens contained acidic mucin. Immunohistochemically, the tumor cells were positive for cytokeratin (CK) AE1/3, CK34BE12, CK5/6, CK7, CK14, p63, alpha-smooth muscle actin (ASMA), S100 protein, p53, Ki-67 (labeling 85%), KIT, PDGFRA and CD56. The tumor cells were negative for CK CAM5.2, CK8, CK18, CK19, CK20, EMA, desmin, CEA, HMB45, CD10, CD34, neuron-specific enolase, chromogranin, synaptophysin, CDX2, MUC1, MUC2, MUC5AC and MUC6. HMB-positive and S100-positive melanocytes were seen in a very few areas. Since characteristic cribriform pattern was recognized in the tumor and the tumor showed epithelial markers, myoepithelial markers (CD14, p63, ASMA, S100 protein) and KIT, the pathological diagnosis of ACC was made. No distant and lymph node metastasis is now seen. The patient will be treated by complete resection. The present cutaneous ACC was unique in that the ACC arose from the epidermis, had melanin pigment, and occurred in ear skin.