Answer: Granulocytic sarcoma

Histology: Within the TUR chips there is a dense infiltrate of loosely cohesive cells. The tumor infiltrates muscularis propria. Individually the nuclei are larger than adjacent endothelial cells. Some contain visible nucleoli yet the tumor lacks abundant cytoplasm and has relatively infrequent mitotic figures. There are scattered eosinophils as well as some mononuclear cells with eosinophilic granules.

Discussion: This case is an example of a granulocytic sarcoma involving the bladder. Alternative designations include extramedullary meyloid tumor, chloroma, or myeloid sarcoma. This patient has no history of a hematological neoplasm and the diagnosis on the bladder was the first manifestation of disease. The typical manner in which a diagnosis of granulocytic sarcoma is made is by somewhat backing into the diagnosis. One would typically perform immunohistochemical stains using a wide battery of epithelial markers as well as standard lymphoma markers. In this case stains for epithelial markers (AE1/AE3, high molecular weight cytokeratin, and CAM5.2) were all negative. In addition stains for lymphoma (CD3, CD20, and CD79a) were negative. A stain for CD56 was also negative against the diagnosis of small cell carcinoma of the bladder. On closer examination of the neoplastic cells, one can appreciate eosinophilic granules within some of the monocytoid cells in addition to admixed eosinophils. The cells are larger than those seen within small lymphocytic lymphoma yet lack the abundant cytoplasm along with prominent nucleoli and numerous mitotic figures seen within large cell lymphoma. These morphological features are typical of granulocytic sarcoma. Once the diagnosis is considered, the diagnosis can be easily verified using immunohistochemistry demonstrating positivity for myeloperoxidase and CD45, as was done in this case. Myeloid sarcomas involving the bladder are extremely rare with less than 10 cases reported in the English literature. In approximately half of these patients there was a history of myeloid leukemia or myelodysplastic syndrome, wherein the remaining half of patients there was no morphological evidence of hematologic disease elsewhere. The outcomes of patients have been variable with some showing no evidence of disease up to 32 months with others dying of disease within a relatively short time due to complications of therapy or showing recurrence of disease following therapy.