Cytokeratin expression patterns in multiple infundibulocystic basal cell carcinoma

Infundibulocystic basal cell carcinoma (IBCC) is a variant of basal cell carcinoma. Sporadic cases usually represent a solitary tumor and multiple IBCC is rare. There have been no reports in which the tumor differentiation is characterized immunohistochemically. We report a case of multiple IBCC which developed on a patient's scalp by performing histopathological and immunohistochemical examinations, using monoclonal antibodies against cytokeratins (CKs). A 76‐year‐old female had noticed multiple small papules on her scalp. She noticed that the tumors were growing when she underwent systemic chemotherapy for metastatic lung cancer. Routine histopathological specimens from skin biopsies revealed findings typical of IBCC. The tumor cells expressed CK14 and CK17. However, CK1 and CK10 were expressed only in a few cells in the inner area of the tumors. The present case is unique in two points. First, multiple tumors developed on the patient's scalp during the systemic chemotherapy for the lung cancer. Second, the tumor showed CK expression patterns characteristic to infundibular and trichilemmal epithelia. Hida T, Saga K, Kimura T. Cytokeratin expression patterns in multiple infundibulocystic basal cell carcinoma.