This study was designed for the histopathological, cellular and biochemical characterization of a skin lesion removed surgically from a young male several months after accidental exposure to cesium-137, with an emphasis on expression of transforming growth factor beta1 (TGFB1) and tumor necrosis factor alpha (TNFA) and the occurrence of apoptosis. Under a hypertrophic epidermis, a highly inhomogeneous inflammatory dermis was observed, together with fibroblastic proliferation in necrotic areas. Immunostaining revealed overexpression of TGFB1 and TNFA inside the keratinocytes of the hypertrophic epidermis as well as in the cytoplasm of the fibroblasts and connective tissue of the mixed fibrotic and necrotic dermis. Inside this dermis, the TUNEL assay revealed areas containing numerous apoptotic fibroblasts next to areas of normal viable cells. Overexpression of TGFB1 was found in the conditioned medium and cellular fractions of both hypertrophic keratinocytes and fibrotic fibroblasts. This overexpression lasted for at least three passages in tissue culture. The present observations were consistent with the central role of TGFB1 in the determination of chronic radiation-induced damage to the skin and a significant involvement of TNFA. In addition, programmed cell death appeared to take place during the remodeling of the mixed fibrotic and necrotic tissue.