Cutaneous leiomyomas and leiomyosarcomas: an immunohistochemical study with p53

Cutaneous smooth muscle tumors are rare and sometimes the differential diagnosis between leiomyoma and leiomyo-sarcoma is difficult and based in very subtle criteria. We therefore tried to investigate the use of p53 in such a conundrum. This marker has rarely been reported in cutaneous leiomyomas and even in more rare occasions, in cutaneous leiomyomas.

We studied 30 benign cutaneous smooth muscle tumors, including angioleiomyomas, common leiomyomas and a symplastic leiomyoma, as well as four leiomyosarcomas and one cutaneous metastasis of leiomyosarcoma. All cases were reviewed in order to confirm the diagnosis, before the cases were included in the study. In all cases, we performed an immunohistochemical study in all cases with p53 and the percentage of positive cells was estimate counting a total of 1000 cells per case.

Six cases from the 31 (19.35%) benign cutaneous smooth muscle tumors showed some expression of p53. The expression of it varied from only occasional cells to 1% of the cells. On the contrary, all leiomyosarcomas investigated showed expression of p53, and in three of the four cases (75%), the marker was expressed by at least 80% of the tumoral cells. Only in one leiomyosarcoma, the marker was expressed by a low percentage (0.5%) of cells. No expression of p53 was found in the only case of symplastic leiomyoma, which was investigated. The case of a cutaneous metastasis of leiomyosarcoma showed expression of p53 by 20% of cells.

We conclude that expression of p53 by a high percentage of cells in a cutaneous smooth muscle cell tumor should be considered as highly suspicious for malignancy.