Alveolar Rhabdomyosarcoma

Comments:
A typical case of alveolar rhabdomyosarcoma (ARMS) shows irregular aggregates of poorly-differentiated round or oval tumor cells. The cellular aggregates are surrounded by hyalinized fibrous septa containing dilated blood vessels.

The central portion of the aggregates shows poorly-preserved cells with degeneration, necrosis, and loss of cellular cohesion with formation of alveolar spaces. At the periphery of the alveolar spaces, the cells are well preserved and line the fibrous septa in a single layer.