Definition:  A very rare benign tumor that may arise in many places, of which the most common is the oral cavity. The tumor is also called "granular cell myoblastomaâ€.

Prevalence: Extremely rare. This tumor occurs in females exclusively.

Etiology: It has been postulated that the etiology could be due to excessive production of estrogens by the fetal ovaries under hCG stimulation[1].

Ultrasound features:   A large solid mass protruding from the fetal mouth.  Polyhydramnios is evident due to inability of the fetus to swallow[2]. Vascular  connections between the tumor and oral floor may be demonstrated using Doppler technique.

Reference

[1] Cussen, L.J., MacMahon, R.A. Congenital granular cell  myoblastoma. J Pediatr Surg 1975; 10:249-53

[2] Schwartz, Z., Katz, A., Zosmer, A., Dreasen, E., Lancet, M., Sagiv, M. Polyhydramnion caused by giant alveolar granular cell myoblastoma. Acta Obstet Gynecol Scan 1986; 65:519-521.