Metastatic Bladder Urothelial Carcinoma Masquerading as Myositis

Skeletal muscle metastases are uncommon, and metastases of urothelial carcinoma to the skeletal muscle are particularly rare. The most common presentation of skeletal muscle metastases is a focal mass, but their clinical and radiographic findings can be diverse. We present an unusual case of a 71-year-old male without prior known history of malignancy who presented with skeletal muscle pain with imaging most consistent with an inflammatory or infectious process but was ultimately determined to be metastatic urothelial carcinoma from the bladder. This case demonstrates the need to keep an expanded differential for muscular pain, particularly when initial treatments are ineffective.