[Folliculosebaceous cystic hamartoma: anatomo-clinical study].

Background: 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.

Materials And Methods: 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.

Results: 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.

Discussion: 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.