Carcinosarcoma of the urinary bladder: Expression of epithelial markers and different expression of heat shock proteins between epithelial and sarcomatous elements

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Abstract
A case of carcinosarcoma composed of both adenocarcinoma and saarcomataus elements in the non‐trigone region of the urinary bladder is presented. The epithelial element was a well to pooriy differentiated adenocarcinome with focal squamous metaplasia. The sarcomatous elements disclosed spindle cell sarcoma with focal epltheliold pattern and myxold change In the stroma, together with chondrosarcomatous and rhabdomyosarcomatous elements. By Immunohistochemical examination, not onty the carcinoma element but also the sarcomatous elements showed a positive lmmunoreaction for cytokeratin (CK), epithelial membrane antigen (EMA) and carcinoembryonic antigen. Some population of sarcomatous elements expressed smooth muscle actin and muscle specific actin (MSA) and a limited portion of epitheliold area showed a positive Immunoreaction for desmin, MSA and myoglobin, Indicating leiomyosarcomatous and rhabdomyosarcomatous differentiation, respectively. Unexpectedly, tumor cells In the chondrosarcomatws element revealed a simultaneous positvity of CK and EMA as well as S‐100 protein. Both epithelial and sarcomatous elements showed an Intensive positive Immunoreaction for p53 and heat shock protein (HSP) 70. However, HSP27 and HSPGO were detected in most epitheilal elements and only in a small number of tumor cells in the sarcomatous area. These findings indicate that sarcomatous elements, Including heterologous elements, may derive from epithelial elements with partial or complete loss of epithelial features, and different factors other than p53 and HSP7O may associate wtth the morphological alteration of carcinoma.