Abstract
Background : Alveolar rhabdomyosarcomas (ARMSs) are a primitive, malignant, neoplasm which show partial skeletal muscle differentiation. Histologically, the alveolar pattern is characterized by anastomosing fibrovascular septa lined with small round tumor cells. In this report, we discuss the characteristic cytological appearance of tumor cells and examine immunohistochemical staining using cell block samples.
Case : A man in his forties was seen in our medical center with swelling in his eyelid. The imaging studies showed an ethmoid sinus tumor with parotid gland and lymph node metastasis. Fine needle aspiration (FNA) was carried out. Three-dimensional clusters predominated. Nuclear moldings were occasionally defined. Tightly grouped nuclei around fibrous stroma were occasionally seen. Cells devoid of cytoplasm were common and dense cytoplasm was also seen. We suspected this was a case of small cell carcinoma. However, we made cell blocks from cytological materials and stained them with antibodies. The tumor cells were positive for myogenin but negative for epithelial markers. Therefore, rhabdomyosarcoma was suspected.
Conclusion : It is difficult to make a definitive diagnosis of ARMS based on cytological findings alone. After careful examination of the cells, immunohistochemical staining makes the best use of limited materials such as cell blocks and is helpful for differential diagnosis.
