Anal canal squamous cell carcinoma metastasizing to the thigh – A “carcinoma en cuirasse”-like rare presentation

Anal canal squamous cell carcinoma (SCC) rarely metastasizes to the skin. We report an unusual case of anal SCC with metastasis to the thigh, presenting as an indurated plaque with “carcinoma en cuirasse”- like features. Cutaneous metastases from gastrointestinal malignancies occur in less than 4% of cases and a diffuse plaque-like presentation is generally associated with breast or lung carcinoma. The case highlights a rare manifestation of anal cancer indicating widespread disease dissemination and poor prognosis. • Cutaneous metastasis is rare and occurs in only 4% of gastrointestinal (GIT) tumors. • The usual presentation is in form of subcutaneous nodules which are small (<2 cm diameter), firm, rubbery, non-tender and most importantly painless. • A diffuse infiltrating pattern of intramuscular plane with overlying skin thickening and redness is very unusual. This type of presentation is mostly seen in carcinoma breast and lung patients and is generally referred as “carcinoma en-cuirasse”. • Premetastatic niche formation via vascular endothelium growth factor A is a proposed mechanism leading to disease spread in late stages via hematogenous and lymphatic route. • Prognosis is generally poor.