GRANULAR-CELL MYOBLASTOMA IN HORSE - A REPORT OF 4 CASES

Spontaneous granular-cell myoblastoma, peribronchial in origin, is reported in 4 Dutch-bred horses, 2 with multiple tumours and 2 each with a solitary tumour. The reported cases of this tumour in horses are now 6, multiple lesions having been reported twice preveiously. Involvement has been unilateral in all cases, the right lung in each except for 1 with a solitary tumour in the left lung. Our histochemical studies indicate the presence of polysaccharides and lipids in the cytoplasmic granules of tumour cells. The equine and human tumours are similar in tinctorial qualities. The former are generally less anaplastic and do not have syncytial cells and fasciculi, a common finding in man. The bronchial epithelium overlying pulmonary tumors is relatively normal in the horses, frequently metaplastic and hyperplastic in man. © 1968, American College of Veterinary Pathologists. All rights reserved.