Bladder
Urothelial carcinoma - invasive
Micropapillary carcinoma

Author: Rugvedita Parakh, M.D.

Revised: 25 September 2018, last major update December 2014

Copyright: (c) 2002-2018, PathologyOutlines.com, Inc.

PubMed Search: Micropapillary carcinoma [title] bladder
Cite this page: Parakh, R Micropapillary carcinoma. PathologyOutlines.com website. http://www.pathologyoutlines.com/topic/bladdermicropapillary.html. Accessed November 18th, 2018.
Definition / general
  • Small nests and papillae with surrounding retraction spaces, resembling ovarian serous borderline tumor
Etiology
  • 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
  • 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
Microscopic (histologic) description
  • 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
Microscopic (histologic) images

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Cytology images

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Contributed by Vanya Jaitly, M.D. and Songlin Zhang M.D.

Diff - Quik

PAP

Cell block



CK7

CK20

CA125

GATA3

HER2

Positive stains
  • 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
  • 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
Board review question #1
Which of the following is true about micropapillary carcinoma of the bladder?

A. A panel of immunostains is typically necessary to determine the site of an unknown primary.
B. The micropapillary component only needs to be reported if 50% or more.
C. Treatment response is comparable to other urothelial carcinoma.
D. Tumor cells appear in small clusters with a vascular axis.
Board review answer #1
A. A panel of immunostains is typically necessary to determine the site of an unknown primary.