Sternomastoid tumor of infancy (fibromatosis colli): diagnosis by aspiration cytology.

Sternomastoid tumor (SMT), as part of the spectrum of muscular torticollis, presents in infants as a discrete mass lesion in the neck, typically unassociated with neck torsion. We describe two patients who underwent fine needle aspiration (FNA) of their neck mass. The cytopathology of these aspirates was composed solely of a mixture of benign-appearing spindle cells and degenerating myofibers. Both infants showed a gradual disappearance of the mass without surgical intervention. We believe that FNA cytology is a diagnostic tool applicable to neonates. Additionally, in the proper clinical setting, aspiration cytology can be diagnostic of the clinicopathologic entity of SMT.