Primary malignant melanoma of the anterior mediastinum in a child

Primary malignant melanoma of the mediastinum is extremely rare. We report a case not previously reported of primary malignant melanoma located in the mediastinum in a 11-year-old boy. The tumor could nest be completely resec ted as a result of extensive invasion of the large blood vessels. Histologi cally, the tumor was heavily pigmented and composed of vague fascicles of s pindle cells intermingled with epithelioid cells. Immunohistochemical analy sis showed vimentin, S-100 protein, Melan-A. and HMB-45 immunoreactivity in most of the tumor cells. Nearly 50% of the tumor cells were also positive for p53. It is suggested that primary malignant melanoma of the anterior me diastinum may have a histogenetic relationship to the recently described ag gregates of nevus cells in the thymus or mediastinal lymph nodes.