Clear cell acanthoma: a rare clinical diagnosis prior to biopsy.

Background: Clear cell acanthoma is a rare, benign epidermal tumor with a clinical hybrid appearance and a distinct histological one. It is frequently mistaken for other clinical lesions.

Objective: To evaluate the frequency that clear cell acanthoma was listed in the clinical differential diagnosis of histologically confirmed specimens.

Methods: A regional dermatopathology lab database was evaluated from January 1998 through March 2008 for histologically diagnosed cases of clear cell acanthoma. Clinical data that was submitted with these cases including differential diagnoses was analyzed.

Results: During this time period of review, 411 histologically confirmed cases of clear cell acanthoma were identified. This entity was listed as a diagnostic possibility in 11 (2.7%) of the cases.

Conclusion: Clear cell acanthoma was rarely listed amongst the differential diagnosis of biopsy proven specimens. This may be due to a variable clinical appearance with overlapping features of several other lesions making it difficult to distinguish, or an entity that is rare and not frequently suspected. Additional studies with dermatoscopy may help to further delineate the reasons for the low diagnostic sensitivity.