Answer: Angiosarcoma

Histology: Most of the tumor consists of sheets of undifferentiated cells with enlarged nuclei with prominent nucleoli (image 2). There is abundant eosinophilic cytoplasm. In areas the tumor is dyscohesive (image 3). There is extensive hemosiderin associated with the tumor (image 4). Focally, there are oval and elongated spaces filled with red blood cells by malignant cells (image 4).

Discussion: The key to diagnosing this case is noting the slightly better differentiated areas with malignant vessels. The presence of extensive hemosiderin deposition is another clue to the vascular nature of the lesion. Confirmation that this was an angiosarcoma was performed with IHC for CD31. If only keratins were performed, the potential would have existed for misdiagnosing the lesion as carcinoma, as epithelioid angiosarcomas can express keratin. There is a variant of urothelial carcinoma with rhabdoid differentiation, yet within the cytoplasm there is a well-defined hyaline round globule occupying most of the cytoplasm. Angiosarcomas of the bladder may be pure or a component of a sarcomatoid carcinoma. In this case, the lesion was pure angiosarcoma. Other vascular lesions in the bladder included hemangiomas, intravascular papillary endothelial hyperplasias (Masson’s vegetant hemangioendotheliomas), arteriovenous malformations (AVM), and epithelioid hemangioendothelioma (EHE). Angiosarcoma of the bladder has a rapidly fatal outcome.

Reference(s):
– Tavora BJ, Montgomery E, Epstein JI. A series of vascular tumors and tumor-like lesions of the bladder. Am J Surg Pathol (August). 32:1213-9, 2008.