Thomsen-Friedenreich (T) antigen: A possible tool for differentiating sebaceous carcinoma from its simulators

The Thomsen-Friedenreich (T) antigen is a cryptic glycoprotein, referred to as tumor antigen or cancer-associated antigen because it is absent or mask ed by some carbohydrates in normal tissues, but present in many human cance rs. The latter include gastrointestinal. lung, pancreatic, mammary, and som e ovarian carcinomas. Cancer cells frequently undergo incomplete glycosylat ion resulting in the appearance of precursor structures that normally would be absent like the case with the T antigen. T antigen can be detected by s everal different reagents including monoclonal antibodies and several plant lectins - e.g., Arachis hypogea (peanut agglutinin). The aim of the curren t study was to evaluate the expression of T antigen in sebaceous carcinoma and to compare it with its simulators. The authors studied the immunohistoc hemical expression of T antigen in 45 skin biopsy and excisional specimens obtained from the archives of their dermatopathology laboratories, includin g 8 cases of sebaceous carcinoma. 15 cases of sebaceous adenoma, 9 cases of sebaceoma. 1 case of basal cell carcinoma with sebaceous differentiation. and 12 cases of basal cell carcinoma with cytologic atypia. Sebaceous carci noma was unique in expressing a strong, diffuse cytoplasmic T antigen react ivity (7 of 8 cases) along the immature basaloid cells and the intermediate cells. However, sebaceous adenoma, sebaceoma, and basal cell carcinomas ex pressed negative reaction in the basaloid cells and mild reactivity in the intermediate cells. Mature sebocytes showed a strong reaction in all cases. The authors concluded that T antigen expression may be a helpful tool in d ifferentiating sebaceous carcinoma from other sebaceous lesions that may si mulate it histologically.