Exfoliation of alveolar rhabdomyosarcoma cells in the ascites of a 50-year-old woman: A diagnostic pitfall with a literature review

Abstract

Alveolar rhabdomyosarcoma (ARMS) is a non-epithelial tumor with skeletal muscle differentiation and typically affects adolescent and young adult patients. Cytological aspects of ARMS in the body fluid have not been well characterized in the literature, making the correct diagnosis difficult. Here, we describe cytological features of ARMS in the ascites of a 50-years-old woman. She presented with an intraabdominal mass and abundant ascites. Aspiration cytology of the ascitic fluid revealed many small-sized discohesive round cells with mild nuclear atypia and prominent nucleoli. Rhabdomyoblastic cells, characteristic of rhabdomyosarcoma, were rarely identified. The presence of cannibalism and 'window' formation, as seen in reactive mesothelial cells, posed a challenge in rendering the diagnosis of ARMS. Histological examination established the diagnosis of ARMS, which was confirmed by the immunohistochemical expression of myogenic markers. In the diagnosis of ARMS from the effusion samples, the diagnostic problems associated with the morphological similarity of ARMS cells to reactive mesothelial cells should be recognized.