Fig. 1

Stromal osseous metaplasia in urothelial carcinoma of the bladder. a Tumor stroma containing multiple bone trabeculae of variable size, separated by loose fibrous connective tissue with osteoid seams (Hematoxylin and Eosin Stain × 200). b Osteoid and bone trabeculae outlined by large cells with abundant cytoplasm and multinucleated giant cells, corresponding respectively to osteoblasts and osteoclasts. Transitional cell carcinomatous component is seen on the left. (Hematoxylin and Eosin Stain × 400). c Positive and diffuse membrane staining of osteoblasts with CD56 antibody. d Strong positive cytoplasmic staining pattern of osteoclasts with CD68 antibody