Malignant granular cell tumor.

A case of a granular cell tumor with a malignant behavior is described. Several repeated biopsy specimens, a resection specimen, and the metastatic lesions were compared with one another. Consecutive specimens showed increasing atypia. Electron microscopy of the metastatic lesions confirmed the granular cell nature of the tumor. The historic aspects of histogenesis are briefly discussed. The findings agree with a presently accepted origin from a primitive mesenchymal cell.