[Folliculosebaceous cystic hamartoma: anatomo-clinical study]

Folliculosebaceous cystic hamartoma (FSCH) is a relatively recently described malformation with follicular and sebaceous components and a particular type of stroma with adipocytes. We conducted an anatomo-clinical study in order to clarify the clinical and histological characteristics of FSCH.

We included all cases of FSCH diagnosed between 1985 and February 2011 at our dermatopathology laboratory. Clinical information was obtained from medical records and requests for histological examination.

We studied 25 cases of FSCH in 25 patients of mean age 51 years. The sex ratio was 1.3. The mean disease duration was 9 years. Lesions were described mainly as flesh-colored, occasionally pedunculated nodules and were found primarily on the face (60%). The diagnosis of FSCH had never been mentioned by the clinician. Histological examination revealed in all cases one or more follicular cystic structures surrounded by sebaceous glands in a stroma containing adipocytes. A number of variants were identified, such as the presence of a mucinous stroma, a neuroid component with protein S 100 expression, and rudimentary hair follicles in adjacent dermis. One case involved a proliferating cyst while another was on the scalp in the area of pre-existing radiodermatitis. Only one relapse was noted, 5 years after the initial excision.

FSCH is a benign, underdiagnosed lesion, localized on the face, particularly on the nose. It is dome-shaped or pedunculated and grows slowly. Differential diagnoses include nevus lipomatosus superficialis and "sebaceous" trichofolliculoma. FSCH can be readily identified by the presence of adipocytes and a fibrous stroma. One case was unique in its appearance of a large pedunculated nodule with a proliferating cyst. Prior to the invidualization of this entity, such cases were interpreted as nevus lipomatosus superficialis or "sebaceous" trichofolliculoma, although their histological appearance was inconsistent with such a diagnosis.