GRANULAR cell myoblastoma and rhabdomyoma are the two tumor types, both rare, arising from striated muscle cells. The myoblastomas were described originally as "Myoblastenmyome" by Abrikossoff1 in 1926. At that time he regarded them as neoplasms due to faulty excessive regeneration subsequent to injury of striated muscle. In 1931, realizing that some of these tumors arose in areas devoid of striated muscle, he postulated2 their origin from primitive myoblasts representing embryonal rests. He classified myoblastomas into four histopathologic types: (1) those consisting of granular myoblastic cells without the presence of striation, (2) the same type with the addition of occasional faint striations, (3) hypertrophic forms consisting of large multinucleated cells and (4) malignant myoblastic myomas consisting of pleomorphic cells, some areas showing differentiation and striations and others frankly sarcomatous in appearance.
On gross examination, myoblastomas are tumors varying in diameter from 0.5 to 2 cm., although they occasionally