Effusion cytology of desmoplastic small round cell tumor of the pleura. A case report.

Desmoplastic small round cell tumor is a recently described neoplasm with multidirectional differentiation. Although it occurs predominantly in adolescent males as an intraabdominal mass with multiple peritoneal implants, we report a case with primary pleural involvement. The cytologic features correspond to previously reported histologic findings and include tightly cohesive clusters of small round poorly differentiated malignant cells with accompanying desmoplastic stromal cells. Immunohistochemical studies revealed characteristic reactivity to epithelial markers, desmin and one neuroendocrine marker (chromogranin). We believe that together with clinical and immunohistochemical data, desmoplastic small round cell tumor can be diagnosed in effusion or aspiration cytology specimens.