Cutaneous cylindroma with malignant transformation

Background. Malignant cutaneous cylindroma is a rare tumor. It has been described in 26 cases, both in the solitary form and in the autosomal dominant inherited multiple tumor form. The authors present two new cases that occurred in one family with a history of multiple cylindromas. Methods. Clinical and histopathologic data of both tumors were compared with those of 26 other cases in the literature. Immunohistochemical examinations were performed. Results. The malignant tumors were distinguished from the benign lesions by rapid growth, long‐standing ulceration, or bleeding. Histopathologic examination showed a well‐differentiated carcinoma in one patient and a poorly differentiated tumor in the other. In the latter, lymph node metastasis developed, and the patient died 2.5 years later. Histopathologic criteria of malignancy included cell pleomorphism, frequent mitoses and loss of jigsaw pattern, peripheral palisading, hyaline sheaths, and dual cell population. Conclusions. These observations are in accord with those in the literature. Malignant cutaneous cylindroma developed more often in the multiple tumor form than in the single tumor form. Malignant cylindroma is an aggressive carcinoma with a tendency to local destructive growth and metastases.