A 42-year-old man consults a physician because he has a “lump” on his forearm. Examination of the arm demonstrates a 3-cm diameter nodule protruding above the forearm surface. The lesion is covered with apparently normal skin and is soft and freely movable. It location appears to be subcutaneous. The lesion has been slowly growing over the past 2 years, and the patient has experienced no discomfort. He has consulted a physician at this time because his wife keeps pestering him to get something done about it. Which of the following is the most likely diagnosis?
A. Capillary hemangioma
B. Dermatofibroma
C. Intradermal nevus
D. Lipoma
E. Seborrheic keratosis
Explanation: The correct answer is D. This is probably a lipoma, which is a benign mass lesion composed of mature adipose tissue bound by a limiting membrane. (Another possibility is an epidermoid cyst, which can be indistinguishable clinically from lipoma.) Lipomas are very common, and patients may have more than one lipoma. Common sites include the trunk, nape of the neck, and forearms. The lesions are only rarely malignant, although a rapidly growing lesion should be biopsied to make sure of the diagnosis. They are usually asymptomatic; a small percentage are painful. They can be treated with surgical excision or liposuction.
Capillary hemangioma (choice A), also known as strawberry mark, is a bright red, vascular lesion that usually develops shortly after birth and then often involutes by late childhood.
Dermatofibroma (choice B) causes a firm, red to brown, small papule or nodule that is most frequently found on the legs.
Intradermal nevus (choice C) causes a flesh colored to black, elevated, lesion that is usually 3 to 6 mm in size.
Seborrheic keratosis (choice E) causes a pigmented, superficial, usually warty, epithelial lesion