Alveolar rhabdomyosarcoma

The typical appearance of alveolar rhabdomyosarcoma is that of fibrovascular septae that are lined with densely packed ovoid to round tumor cells and separated by pseudo-alveolar spaces, which vaguely resemble pulmonary alveoli. A tumor must have a predominant (>50%) alveolar component or bear the characteristic translocations t(1;13) or t(2;13) to be subtyped as alveolar (H&E, 200x original magnification).