Unusual second malignancies following radiation therapy: subcutaneous pleomorphic rhabdomyosarcoma and cutaneous melanoma. Two case reports.

BACKGROUND

Among nonepithelial second neoplasms which are known to be induced by irradiation, rhabdomyosarcomas are extremely rare, and melanomas are infrequent. We report a high-grade sarcoma with rhabdomyoblastic differentiation, which appeared 30 years after megavoltage irradiation for an endometrial adenocarcinoma, and a malignant melanoma which arose after 6 years in the irradiation field of a fibrosarcoma.

METHODS

Histology and immunohistochemistry were performed in both cases. In the first case, electron microscopy was also performed. In the second, the previous tumor was re-evaluated.

RESULTS

The first case showed histological, immunohistochemical and ultrastructural features of a rhabdomyosarcoma. In the second case, a lentigoid malignant melanoma was histologically and immunohistochemically demonstrated, whereas the previously resected tumor was a fibrosarcoma negative to melanoma markers.

CONCLUSIONS

Rare cases of rhabdomyosarcomas and melanomas are induced by irradiation, although in some cases other factors (i.e., genetic risk, chemotherapy) may have a prominent etiopathogenetic role in their development. A close follow-up and a careful examination of the irradiated area should facilitate an early diagnosis of these aggressive postradiation second neoplasms.