A case of juvenile nasal polyp with severe atypical cells.

We report a case of nasal polyps with stromal atypical cells in a 5-year-old boy, whose cytologic features simulated rhabdomyosarcoma. A polypoid lesion of the left nasal cavity grew rapidly and showed a necrotic, hemorrhagic surface. Aspiration cytology showed spindle to polygonal cells with 1 or 2 oval nuclei in the necrotic and hemorrhagic background. Conspicuous nucleolei were observed in these cells. Cytologically, possible embryonal rhabdomyosarcoma was initially suspected. However, histology disclosed a few atypical cells without mitosis scattered in edematous stroma, and finally was interpreted as nasal polyps with stromal atypia. It was suggested that the number of atypical cells, low mitotic rate, and absence of intracytoplasmic glycogen in atypical cells are important in cytologically differentiating this from rhabdomyosarcoma.