GRANULAR cell myoblastoma is an uncommon and poorly understood tumor which has fascinated pathologists and surgeons for several decades. Many theories have been proposed in regard to its development and histogenesis. The term "myoblastoma" is misleading since there is no proof that it is a tumor of myoblasts. The more popular theory is that it is a tumor of Schwann cells.1Fischer and Wechsler2submitted convincing evidence to that effect based on electron microscopy and histochemical studies. Other theories are that it is a tumor of fibroblasts or mesenchysmal cells. Willis3denies its neoplastic origin and states that it is the result of trauma. To support his theory, he cites, in addition to the lack of mitoses and slow growth, the peculiar associated epithelial hyperplasia. Atrophy is the common epithelial reaction to tumor. Gray and Gruenfeld4feel that perhaps it represents necrobiotic changes in muscle fibers,
