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Bladder

Urothelial carcinoma-invasive

Micropapillary carcinoma


Reviewers: Rugvedita Parakh, M.D., HCG Oncology (see Reviewers page)
Revised: 7 June 2011, last major update June 2011
Copyright: (c) 2003-2011, PathologyOutlines.com, Inc.

Definition
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● Small nests and papillae with surrounding retraction spaces, resembling ovarian serous borderline tumor

Etiology
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● May be due to reversal in cell polarity due to MUC1, normally on apical surface, being localized on stroma-facing surface of cells (Mod Path ol 2004;17:1045)

Clinical features
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● Adults, 80% men, mean age 67-69 years
● Incidence of 0.7%
● Usually high grade and high stage at presentation with marked nodal metastases and extensive lymphovascular invasion
● Presence of micropapillary pattern in otherwise conventional urothelial carcinoma is associated with advanced tumor stage and poor prognosis; if surface micropapillary carcinoma is present in biopsy without muscularis propria, deeper biopsy to determine muscular invasion is recommended (Am J Surg Pathol 1994;18:1224)

Case reports
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● 45 year old man with mixed micropapillary and trophoblastic bladder carcinoma (Hum Pathol 2004;35:382)
● 70 year old man with gross hematuria and indurated mass in bladder (Arch Pathol Lab Med 2005;129:e53)

Micro description
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● Small nests and papillae with surrounding retraction spaces, resembling ovarian serous borderline tumors, but without psammoma bodies
● Delicate papillae 1-4 cell layers thick with thin stromal cores and numerous secondary micropapillae
● Micropapillae may lack fibrovascular cores and show hierarchical branching
● Confluent retraction spaces are characteristic, and simulate lymphovascular invasion
● Multiple nests in same retraction space is common
● Nuclear grade is typically high in deeper portions; may have lower grade appearance at surface
● Most tumors are muscle invasive
● Numerous mitoses and frequent true lymphovascular invasion
● Edematous stroma with chronic inflammatory infiltrate
● Often mixed with urothelial carcinoma in primary, but metastases usually have only micropapillary pattern

Micro images
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Various images



MUC1 staining

Positive stains
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● MUC1 is limited to basal surface of cells, compared to apical, intracytoplasmic or intracellular staining in conventional carcinomas
● EMA, CK7, CK20; variable HER2 and CA-125

Differential Diagnosis
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Ovarian borderline tumors: clinical history; no urothelial component; psammoma bodies are common
Invasive urothelial carcinoma with stromal retraction: no micropapillae; stromal retraction is negative for CD31, CD34, D2-40
Papillary nephrogenic adenoma:

Additional references
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Am J Surg Pathol 1994;18:1224, Hum Pathol 2010;41:1159

End of Bladder > Urothelial carcinoma-invasive > Micropapillary carcinoma


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