P53 IMMUNOHISTOCHEMISTRY IN MALIGNANT FIBROUS HISTIOCYTOMAS AND OTHER MESENCHYMAL TUMORS

In this study we analysed by immunohistochemistry the expression of p53 protein in 14 malignant fibrous histiocytomas (MFHs), 22 other types of sarcoma (eight leiomyosarcomas. four rhabdomyosarcomas, four liposarcomas, two fibrosarcomas, two chondrosarcomas, one malignant schwannoma, and one dermatofibrosarcoma protuberans), and 25 non-malignant mesenchymal lesions (eight dermatofibromas, four cases of nodular fasciitis, three leiomyomas, three fibromatoses, two epithelioid leiomyomas, two neurofibromas, one schwannoma, one myositis ossificans, and one giant cell tumour of tendon sheath). Four MFHs and nine other types of sarcoma (four leiomyosarcomas, two chondrosarcomas, one liposarcoma, one fibrosarcoma, and one dermatofibrosarcoma protuberans) showed nuclear positivity for p53. Of the benign soft tissue lesions, p53 positivity was observed in two fibromatoses, one nodular fasciitis, and one dermatofibroma. The number of p53-positive cells in these benign lesions was considerably smaller than that in most of the p53-positive sarcomas. The p53 positivity in MFHs and other types of sarcoma indicates that p53 gene alterations may play a part in the neoplastic transformation of these tumours. The occurrence of p53 positivity in benign mesenchymal lesions suggests that sometimes p53 protein may accumulate in cells without an associated malignancy. Because of this, p53 immunoreactivity cannot, by itself, be used as a criterion of malignancy. According to our results, p53 positivity in over 1 per cent of tumour cells in mesenchymal lesions favours malignancy.