Clear cell acanthoma of Degos

A clear cell acanthoma of Degos is an uncommon benign epidermal lesion containing clear cells with a glycogen-rich cytoplasm. It most commonly arises as a solitary lesion on the lower legs.

The chapter is set out as follows:

• Age - usually affects adults with a peak incidence between 50 and 60 years of age
• Can be asymptomatic although surface oozing is not uncommon and occasionally lesions can bleed

Distribution

• Normally solitary but occasionally multiple lesions
• Lower legs most commonly affected site

Morphology

• Size varies from 3-20 mm in diameter
• Pink-red, occasionally brown
• Plaque-like or nodular
• Abrupt margin
• A thin surface scale that is adherent peripherally and leaves a moist or bleeding surface when removed
• Vascular punctae may be visible on the surface

Dermoscopic appearance (hover over terminologies for description)

• The most characteristic feature of CCA is the ''string of pearls'' vascular pattern in which dot or coiled (glomerular) vessels are arranged in serpiginous pattern (for more information on vessels refer to the chapter Vessel patterns in dermoscopy)
• The background colour is a homogenous pale pink or light red
• Shiny white lines and orange crusts may be present

• If there is diagnostic uncertainty a biopsy will be required - the histopathological features are characteristic. These include psoriasiform acanthosis with pale periodic acid–Schiff (PAS) positive glycogen‐rich keratinocytes (clear cells). The cytoplasm of the clear cells contains an abundance of glycogen, which on electron microscopy is seen to displace tonofibrils. There is intercellular oedema and an infiltrate often containing many polymorphonuclear leukocytes forming parakeratotic microabscesses. The papillary dermis is oedematous and the superficial capillaries and veins are increased in number (reference Rook's Textbook of Dermatology) 

• Lesions are benign and so once diagnosed no further treatment is required