Fine-needle aspiration biopsy of childhood rhabdomyosarcoma: reevaluation of the cytologic criteria for diagnosis.

The distinction between rhabdomyosarcoma (RMS) and the other small round blue cell tumors of childhood has therapeutic implications which stress the importance of a correct diagnosis. In attempts to reevaluate the cytologic criteria of this entity, we reviewed a series of 17 fine-needle aspiration biopsies and three touch imprints from soft tissue masses. All cases had been histologically confirmed except for two cases that only had immunocytochemical and ultrastructural confirmation. The features occurring most commonly include a uniform population of tumor cells arranged as single cells and cohesive aggregates. The cells were predominantly round/polygonal, with uniform nuclei and scant to moderate amounts of cytoplasm. The nuclear chromatin was most often finely granular and hyperchromatic, while nucleoli were inconspicuous. Binucleated and multinucleated cells were found in 17 of the 20 smears. Intracytoplasmic vacuoles were present in 17 cases, ranging from occasional in one case, a few in 10 cases, and very numerous in six cases. We conclude that the presence of bi/multinucleated cells is an important clue for the diagnosis of RMS on fine-needle aspiration biopsy.