Abstract

Described in 1962, Degos acanthoma, also known as clear cell acanthoma or pale cell acanthoma, is a skin lesion with a hitherto unknown etiology and controversial mechanisms of development. Despite the numerous clinical variants and cases that have been studied, it is still questionable whether it has an inflammatory or neoplastic origin. It follows that the histopathologic differential diagnosis potentially includes both inflammatory dermatoses and neoplasms. We present the case of a 79-year-old male with multiple brown-red, rounded, up to 1.3 cm in diameter, well-circumcised, scaly/crusty lesions in the right lower back for several months. A shave biopsy of the largest lesion revealed a psoriasiform acanthosis with rare basal mitoses, without atypia or malignancy. Histologic features included hypogranulosis, confluent parakeratosis neutrophils scattered throughout the epidermis, pallor of keratinocytes and an epidermal collarette. Pale cell acanthoma of Degos was diagnosed. A month later, all the lesions were excised, revealing a background of pale cell acanthoma but in many areas epidermal atypia consistent with squamous cell carcinoma in situ. The lesion could potentially be characterized as an atypical or malignant variant of Degos acanthoma, which would potentially lend credence to the theory that Degos acanthoma is a neoplastic process. Or is it simply an incidence of a “collision tumor” or squamous cell carcinoma in situ arising secondarily in a Degos acanthoma? Based on this experience, complete excision of the lesion with an assessment of the resection margins is strongly recommended in all cases of Degos acanthoma.

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