Folliculotropic T cells in regressive basal cell carcinoma of skin

The histologic features of regression may be found in some basal cell carci nomas (BCCs), and it is known that T-cell infiltrates have a significant ro le in host defense against this tumor. We examined 945 hair follicles (HFs) adjacent to 150 regressing BCCs of skin for the presence of inflammatory i nfiltrates and compared the results against 315 HFs in 50 samples of normal skin. Focal T-cell infiltrates localized mainly to the upper portion of th e HFs were found in 14.5% of the follicles adjacent to regressing BCCs. A s tatistically significant increase of inflammation in HFs was observed in BC Cs with active regression compared with BCCs with inactive and mixed regres sion (P < 0.05). An increase in the number of HFs involved by T lymphocytes was also found in regressing BCCs compared to normal skin (P < 0.00005). T hese data suggest that the damage to the follicles is concordant with activ e regression of BCCs. We speculate that the immunemediated regression of BC Cs is not only specifically directed to the cells of the tumor but may also induce activated lymphocytes with cytotoxic capability to cross react with the follicular epithelium.