Squamous cell carcinoma antigen in patients with cutaneous disorders.

Serum levels of the tumor marker squamous cell carcinoma antigen (TA-4) were examined in patients with nonneoplastic dermatologic diseases. The majority of patients with significant disease had elevated levels of this antigen. The percentage of involved skin surface area correlated with serum squamous cell carcinoma antigen levels. Psoriasis and atopic dermatitis have different effects on squamous cell carcinoma antigen levels. Kidney failure also causes elevated levels. Squamous cell carcinoma antigen is not a reliable tumor marker in patients with squamous cell carcinoma at any site when these patients also have a cutaneous disorder that involves more than 2% of the skin surface area or when they have kidney failure.