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26 January 2011 – Case of the Week #195
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Case of the Week #195
A 40 year old woman presented with a bladder tumor, and had a TURBT.
What is your diagnosis?
S100 and HMB45 staining
Chromogranin, synaptophysin and NSE staining
Paraganglioma of bladder
The microscopic sections show a tissue mass with adjacent benign urothelium, lamina propria and muscularis propria. The mass contains occasional nests of cells ("zellballen" pattern) but primarily sheets of large, pleomorphic malignant cells with a vascular stroma. The tumor cells have abundant cytoplasm with brown melanin pigment and large vesicular nuclei, but no prominent nucleoli and only rare mitotic figures. Immunostaining shows scattered staining for S100 protein, but no HMB45 staining. There is also strong staining for Chromogranin-A and synaptophysin. Ki-67 staining (not shown) revealed nuclear staining of 5% of tumor cells.
Paraganglioma, also called extra-adrenal pheochromocytoma, is uncommon in the bladder. It typically affects young women (median age 44 years), in contrast to urothelial carcinoma, which has a median age of 70 years.
Tumors have the classic zellballen pattern or diffuse patterns of large polygonal cells with abundant eosinophilic granular cytolasm. The nuclei are usually fairly uniform, and a delicate fibrovascular stroma is usually present. Although there may be involvement of muscularis propria, there is usually no desmoplasia. Melanin pigmentation is rare, but does not appear to affect prognosis (Cancer 1997;79:398).
The differential diagnosis includes:
- carcinoid tumor: may have nesting pattern, but is keratin+
- urothelial carcinoma: usually older patients, much more common, usually more pleomorphism, also keratin+ (Am J Surg Pathol 2004;28:94)
- melanoma: the "great imitator" may have a focal nesting pattern, but has prominent mitotic figures; it is usually strongly S100+ and HMB45+, and negative for neuroendocrine markers.
Treatment consists of excision (partial cystectomy). Tumors may recur or metastasize in 5-15%, although these cases often cannot be predicted.
Additional references: Bladder - paraganglioma
Nat Pernick, M.D., President
and Liz Parker, B.A., Associate Medical Editor
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