Cutaneous pathobiology mediated by chemotherapy

A histopathologic study of side effects of chemotherapy on normal skin was made by light microscopy and radioautography after incorporation of tritiated thymidine. Two psoriatic patients were studied after methotrexate treatment and one after polychemotherapy for an osteosarcoma 2--5 days after administration of methotrexate. Four biological effects can occur: cellular death, recruitment of cells from a resting phase into the cell cycle of proliferation, synchronization of cells in that cycle and blockage of cells in specific phases. Sub-lethal signs and necrosis were recognized in the epidermis as vacuolar alterations, cytoplasmic inclusions, swelling of keratinocytes, apoptosis and dyskeratosis. Bullae resulted from epidermal necrolysis. The labelling index of normal looking keratinocytes was very high. Within capillaries, plump and hyperchromatic endothelial cells were increased in number, as was their labelling index. Fibroblasts and cells of the eccrine glands were also labelled in number. The number of labelled nuclei within these cell lines reflects the recruitment and synchronization in the cell cycle and the blockage in S phase.