June 2003

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Diagnosis: Polypoid Sebaceous Hamartoma with connective tissue and organoid features

Histopathology
There is focal hyperplastic sebaceous glands arranged around keratin-filled cysts, which do not have features of normal hair follicle development (Figs. 2,3). Within the dermis there are proliferations of fatty and loose fibrous tissue (Fig 4).

Discussion
Hamartomas are characterized by an abnormal arrangement of normally present tissues. Sebaceous hamartomas are quite uncommon and include folliculosebaceous cystic hamartoma, and steatocystoma. Nevus sebaceous involve sebaceous as well as other appendageal components. The folliculosebaceous cystic hamartoma presents as a solitary papule or nodule usually on the face with a predilection for the nose; two cases have been reported on the ear and upper back. The age of onset is between 4 and 47, though most arise in adulthood. The clinical differential diagnoses include nevus, neurofibroma, and adnexal tumor. In contrast to other sebaceous neoplasms, there does not appear to be an increased incidence of Muir-Torre Syndrome. The optimal treatment is a simple excision and recurrence is rare.

References:
1.Kimura T, Miyazawa H, Aoyagi T, et al. Folliculosebaceous cystic hamartoma. A distinctive malformation of the skin. Am. J. Dermatopathol (1991) 13:213.

2.Templeton SF, Folliculosebaceous cystic hamartoma: a clinical pathologic study. J. Am. Acad. Dermatol (1997) 36: 502. Weedon, D. Skin Pathology (2002).

My thanks to Dr. Larry Wang for preparing this case.