Man in his 60s with a bladder mass   

History and images

Our appreciation is extended to Dr. Nada Shaker, Department of Pathology, Wexner Medical Center, Ohio State University, Columbus, OH, for contributing this case.

History: A man in his 60s with a past medical history of hypertension and dilated cardiomyopathy presented with a bladder mass. Upon excision, tumor examination revealed a skeletal muscle proliferation tumor. Tumor invasion was found within the lamina propria, muscularis propria, and perivascular adipose tissue. No lymphovascular invasion or evidence of lymph node neoplasia was found. Immunostaining was positive for Ck20 (transurethral), myogenin (focal), synaptophysin, desmin, chromogranin (focal), vimentin, and INSM1, and negative for CK20, AE1/AE3, SMA, Ck7, S100, GATA3, p63, CAM 5.2, and SOX10. On gross examination, 40% of the urinary bladder mass was necrotic. Complete excision was warranted.

Click images to enlarge.

Hematoxylin and eosin staining:

Desmin staining:

Vimentin staining:

Smooth muscle actin staining:

What is the most likely diagnosis?
Rhabdomyosarcoma of the bladder (RMS), alveolar pattern
High-grade sarcoma