Case 5

M 65. 3 cm erythematous eroded plaque buttock, unresponsive to suprapotent steroids. ?IEC.

• A Invasive squamous cell carcinoma

• B Non-tuberculous mycobacterial infection

• C Clear cell acanthoma

• D Pyoderma vegetans

PAS

Case 5

• A Invasive squamous cell carcinoma

• B Non-tuberculous mycobacterial infection

• C Clear cell acanthoma

• D Pyoderma vegetans

Polypoid / polypous CCA

Typical clear cell acanthomaWell demarcated erythematous plaque with peripheral collarette.

Frequently misdiagnosed clinically.

Sharply circumscribed “psoriasiform” epidermal proliferation of pale cells containing abundant neutrophils with sparing of the acrosyringium / acrothrichium.

?Neoplastic ?inflammatory.

Case 5

• A Invasive squamous cell carcinoma

• B Non-tuberculous mycobacterial infection

• C Clear cell acanthoma

• D Pyoderma vegetans

“Polypoid” CCA: learning points

• A small subset of CCAs are associated by irregular epidermal proliferation.

• Such lesions may be potentially mistaken for a SCC, particularly in partial biopsies.

• Useful clues: pale glycogen-rich cytoplasm, intraepithelial neutrophils, sparing of the acrosyringium / acrotrichium, sharp line of demarcation at the periphery.

• Awareness is important as diagnostic clues are not always obvious in small biopsies.