上唇部皮下に発症したｍｉｃｒｏｃｙｓｔｉｃ ａｄｎｅｘａｌ ｃａｒｃｉｎｏｍａの１例

Abstract

Microcystic adnexal carcinoma (MAC) is a rare malignant tumor of skin appendages. This tumor arises most commonly in the upper lip in the maxillofacial region. MAC is characterizedby a relatively slow clinical course, a strong tendency toward infiltration, and a low frequency of remote metastasis. Recently, we treated a case of MAC arising in the labial subcutaneous region. The patient was a 54-year-old man who noticed a mass in the right upper lip nearly 20 years ago. Since the tumor gradually became larger, he was referred to our hospital by a nearby clinic. At presentation, an extremely hard and immovable induration (20×15mm) was discovered at the upper lip. A benign tumor derived from a skin appendage was diagnosed on the basis of the clinical course of 20 years. Surgery was recommended, but the patient refused. He therefore underwent follow-up observation. When the tumor rapidly enlarged in March 2005, squamous cell carcinoma was diagnosed on the basis of a biopsydone in June. The tumor was resected with the patient under general anesthesia. Histopathological examination revealed no relation between the tumor and the skin, and imaging studies revealed continuous infiltration to the deep muscular layer. Proliferation of atypical basal cell-like squamous cells was found with microcystic lesions in the parenchyma of thetumor. On the basis of these findings, MAC was diagnosed. Neither local recurrence nor remote metastasis has been detected as of 2 years after resection.