Pathologic Findings in Small Cell Bladder Carcinoma Overview of Small Cell Bladder Cancer Pathology
- Author: Zhong Jiang, MD; Chief Editor: Liang Cheng, MD more...
Overview of Small Cell Bladder Cancer Pathology
Small cell carcinoma of the urinary bladder accounts for only 0.3-0.7% of all bladder tumors. All small cell carcinomas of the urinary system identified so far have been located in the urinary bladder, most commonly in the dome and vesical lateral wall.
For more information, see Bladder Cancer, as well as Pathologic Findings in Squamous Cell Bladder Carcinoma and Cystoscopy.
Small cell carcinoma of the urinary bladder usually has a polypoid or nodular appearance and often has an ulcerated surface. Pathology gross examination reveals a solid tumor mass that originates from the mucosa and often penetrates deeply into the bladder wall.
In 68% of small cell carcinoma of the urinary bladder cases, they are mixed with classic urothelial carcinomas or adenocarcinomas of the bladder. The histologic features of small cell carcinoma are the same as those in other organs. The tumor is made of sheets and nests of loosely cohesive, small, round or oval cells with very scant cytoplasm (see the image below).
The tumor cell nuclei are hyperchromatic with coarsely granular chromatin. Nuclei molding can be seen. Mitosis is present and may be frequent. Nucleoli are absent or small. Tumor necrosis is often present. Urinary cytology often reveals single and loosely cohesive clusters of tumor cells with typical small cell carcinoma morphology.
Neuroendocrine markers, such as chromogranin A, synaptophysin, CD56, and neuronal specific enolase, are often focal or diffusely positive for these tumors by immunohistochemical method, and they are useful tools to help establish a diagnosis. (See the image below.)
However, a definitive diagnosis can be rendered based on morphology alone; even the immunohistochemical method fails to demonstrate expression of these markers. A cocktail of cytokeratin markers is often nonreactive, but low molecular cytokeratin, CAM5-2, and epithelial membrane antigen (EMA) are mostly positive.[3, 4]
As in small cell carcinoma of other organs, the tumor cell exhibits abundant genomic aberrations. Typically, every tumor cell has more than 10 in number. The most frequent changes include deletions of 10q, 4q, 5q, and 13q and gains of 8q, 5p, 6p, and 20q. It is also suggested that acquisitions of genomic alterations in typical invasive urothelial carcinoma lead to the development of small cell carcinoma. Genomic DNA amplifications are also found in many loci where oncogenes are located.
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