Development of spindle-shaped cells and chondroid cells from androgen-dependent Shionogi carcinoma 115. A light and...

Androgen-dependent Shionogi carcinoma 115 (SC115) is an undifferentiated medullary carcinoma consisting of compact round cells. However, when host male DS mice were castrated 2 weeks after tumor transplantation, tumors composed of compact round cells, spindle-shaped cells and chondroid cells grew 4 weeks after castration. Compact round cells with desmosomes were arranged in solid nests and exhibited immunoreactivity for keratin protein. Spindle-shaped cells had prominent rough endoplasmic reticulum, and appeared to secrete collagen. Chondroid cells had the characteristics of chondrocytes. The light and electron microscopic features were highly suggestive of a transition from compact round cells to spindle-shaped cells, and from spindle-shaped cells to chondroid cells. The histology of this tumor thus suggests that SC115 cells are able to change into chondroid cells via spindle-shaped cells.