A 2-day-old girl was admitted to our university hospital with a tumor of vulva. The tumor was elastic hard with normal skin. Laboratory findings were within normal limits. The tumor was extirpated en bloc uneventfully. It was 3.5x2.0x2.0cm in size and weighted 10 grams. Histologically it was consisted of a mixture of smooth muscle, well differentiated adipose tissue, cartilage, connective tissue and small blood vessels, and was diagnosed as benign mesenchymoma. The benign mesenchymoma is rare tumor. To our knowledge, 68 cases of benign mesenchymoma in infancy and children have been reported in Japanese and English literature, The most common sites of the tumor are the head and neck, trunk and lower extremity. The occurrence of the vulva is very rare as this present case. Because of all the tumor infiltrate to a greater or lesser degree, we recommend wide local excision as the treatment of choice.
