Bladder - Small cell carcinoma

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Bladder

Other carcinomas

Small cell carcinoma

Author: Nat Pernick, M.D. (see Authors page)

Revised: 28 December 2009, last major update - December 2009

Definition

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● Rare bladder tumor resembling counterparts in lung and elsewhere

● A type of poorly differentiated carcinoma

● A morphologic diagnosis - neuroendocrine differentiation is not required

Terminology

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● Also called poorly differentiated small cell carcinoma

Epidemiology

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● Rare, 0.5 to 1.0% of all bladder malignancies

● No age, sex or clinical differences from usual type urothelial carcinoma

Sites

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Etiology

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● In at least some cases, arises from urothelial carcinoma in situ (Hum Pathol 2008;39:1258)

● May arise from totipotent stem cells in submucosa (Semin Oncol 2007;34:15)

Clinical features

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● Pure or with urothelial carcinoma or other carcinomas (diagnose as small cell if any appreciable component, because prognosis is affected by presence of small cell component)

● Occasionally associated with hypercalcemia and ectopic ACTH production

● Most cases are advanced at diagnosis; 65% have metastases at or soon after diagnosis

● Very aggressive (mean survival in months) with rapid development of metastases to regional nodes, liver, bones, peritoneal cavity

● 5 year survival of 8-16% (Cancer 2004;101:957)

● Rarely coexists with tumor cells exhibiting skeletal muscle differentiation (AJSP 2000;24:223)

Prognostic factors

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Case reports

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● 52 year old man (J Cancer Res Ther 2009;5:133)

● 55 year old woman with tumor secreting ACTH (Hum Path 1985;16:313)

● 73 year old man with combined small cell carcinoma and high grade papillary urothelial carcinoma (Archives 2004;128:1055)

Treatment

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● Radical cystectomy unless metastatic disease is present - then need systemic therapy (Cancer 2005;103:1172)

● High response rate to chemotherapy (similar to that used for lung tumors), but overall prognosis is still poor (BJU Int 2009;103:747)

Clinical images

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Gross description (Macroscopy)

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● Usually large polypoid mass anywhere in bladder

Gross images

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Micro description (Histopathology)

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● Tumors with any appreciable small cell component should be classified as small cell carcinoma

● Resembles small cell carcinoma of lung

● Loosely cohesive sheets or nests of small to intermediate sized cells with minimal cytoplasm, hyperchromatic nuclei, stippled or coarsely granular chromatin, indistinct nucleoli, no nuclear overlapping

● Mitotic activity and necrosis are common

● Often coexists with other forms of in situ or invasive carcinoma

Micro images

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Sheets of small cells with scant cytoplasm in lamina propria with unremarkable urothelium

Ill defined nests of cells #1; #2

Invasion of muscularis propria #1; #2

Cords or nests of cells with molding, scant cytoplasm, hyperchromatic nuclei with fine chromatin and mitotic activity #1; #2

Fig a: invasion into muscularis propria; Fig b: c-kit+

Synaptophysin+; mixed small cell and classic urothelial carcinoma shows synaptophysin+ in small cell component

Low power shows uniform cells, suggesting lymphoma or sarcoma; High power shows numerous mitoses and lack of prominent nucleoli

No thumbnails: With low grade papillary urothelial carcinoma #1; #2; #3; Ki-67

Cytology description

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● Numerous tumor cells in loose clusters, cells are larger than lymphocytes, have scant cytoplasm, eccentric nuclei with evenly dispersed but coarse chromatin, indistinct nucleoli

Cytology images

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Mixed small cell and undifferentiated urothelial carcinoma: #1; #2; #3; #4; synaptophysin

Positive stains

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● EMA, CAM 5.2 (dot-like perinuclear pattern)

● Usually neuron-specific enolase, synaptophysin (frequently has neuroendocrine features, AJSP 1987;11:606)

● Variable c-kit (27%, Mod Path 2005;18:320), chromogranin (weak/focal if present), CK7 (Hum Pathol 2005;36:718), TTF1+ (Mod Path 2000;13:238)

● Note: neuroendocrine stains are considered of questionable value by many, since this is a morphologic diagnosis

Negative stains

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● CEA, CK20

● HPV (AJSP 2004;28:901)

Electron microscopy descriptions

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● Few dense core granules

Electron microscopy images

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Molecular / cytogenetics description

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Molecular / cytogenetics images

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Differential Diagnosis

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● High grade urothelial carcinoma: by definition, should lack any appreciable small cell component

● Lymphoma: tumor cells are smaller, positive for CD45, B or T cell markers

● Metastatic small cell carcinoma: usually no associated urothelial carcinoma, need clinical information

Additional references

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● eMedicine

End of Bladder > Other carcinomas > Small cell carcinoma

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