What is clear cell acanthoma of Degos?

Updated: Oct 07, 2019
  • Author: Guy J Petruzzelli, MD, PhD, MBA, FACS; Chief Editor: Gregory Gary Caputy, MD, PhD, FICS  more...
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Clear cell acanthoma of Degos

One of the most common benign epithelial tumors is seborrheic keratosis/senile keratosis, a hereditary lesion that appears in individuals over age 30 years. On the other hand, clear cell acanthoma is a rare, benign epithelial cutaneous tumor. Typically, the clinical presentation of clear cell acanthoma is a solitary nodule of the lower extremities. It is usually pink or red-brown and described as glistening. [14]

Clear cell acanthomas usually range in size from 3-20 mm, and they tend to have a collarette of scale around the edges. Peeling this scale can elicit bleeding.

Upon histologic examination, the epidermis is abruptly interrupted with acanthotic epidermis, resembling psoriasis. The sharp demarcation of the borders of a clear cell acanthoma distinguishes it from psoriasis.

Cells of clear cell acanthoma are translucent because of the presence of glycogen, which can be demonstrated by a periodic acid-Schiff (PAS) stain. For this same reason, the cells within the acanthotic epidermis stain faintly; electron microscopy demonstrates that the defective keratinocytes also contain defects in mitochondria and nuclear structures. [15]

The acanthotic epidermis can also contain dendritic melanocytes, in which melanin granules are interspersed among the abnormal keratinocytes. This presence of melanin provides pigmentation to the benign tumor, and this occurrence has been termed pigmented clear cell acanthoma.  [16]

Clear cell acanthoma usually stains positive for epithelial membrane antigen and negative for carcinoembryonic antigen. With anti-keratin antibodies, the clear cell acanthomas stain for AE1 and AE3 but not for CAM5.2. In fact, clear cell acanthoma possesses a staining pattern similar to that of inflammatory dermatoses such as psoriasis vulgaris, lichen planus, and discoid lupus erythematosus and might actually be a localized form of inflammatory eruption rather than a true neoplasm.

Variants of the clear cell acanthoma have been noted and include polypoid, giant, multiple, and eruptive. It can be treated by surgical excision and cryotherapy, although spontaneous involution has been reported.

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