Kidney tumor
Renal pelvis: Urothelial carcinoma and variants
Urothelial carcinoma of renal pelvis - micropapillary


Topic Completed: 1 September 2015

Revised: 18 September 2019

Copyright: 2003-2019, PathologyOutlines.com, Inc.

PubMed Search: Urothelial carcinoma of renal pelvis micropapillary

Related Topic: Urothelial carcinoma of renal pelvis


Nicole K. Andeen, M.D.
Maria Tretiakova, M.D., Ph.D.
Page views in 2018: 179
Page views in 2019 to date: 119
Cite this page: Andeen NK, Tretiakova M. Micropapillary. PathologyOutlines.com website. http://www.pathologyoutlines.com/topic/kidneytumormalignanturothelialcarcinomasubtypesmicropap.html. Accessed September 18th, 2019.
Definition / general
  • High grade neoplastic urothelial cells in small infiltrating clusters of micropapillary aggregates within lacunae / empty spaces or slender micropapillae on the surface, usually lacking true fibrovascular cores
  • Morphology may be focal or extensive; no specific % cutoff exists to designate as micropapillary
  • Recommended to include % of micropapillary component in report (Mod Pathol 2009;22:S96)
Essential features
  • Clinically aggressive, "inside out" growth pattern with peripherally oriented pleomorphic nuclei and multiple nests within the same lacunar space
  • Lymphovascular invasion nearly always present
Epidemiology
Sites
  • Renal pelvis and upper ureter
Pathophysiology
  • "Inside out" growth pattern
  • Microvilli and glycoproteins
    • Usually seen on luminal surface
    • Are present on the basal / stromal facing surface
  • Reverse polarity likely affects stromal interaction, and may facilitate stromal and vascular invasion via metalloproteinases, cadherin / catenin complex (Am J Clin Pathol 2004;121:857), or other mechanisms (Adv Anat Pathol 2004;11:297, Mod Pathol 2004;17:1045)
Clinical features
  • Aggressive; usually associated with high stage at presentation, nodal metastases, distant metastases and poor prognosis (Arch Pathol Lab Med 2009;133:62)
Prognostic factors
Case reports
Treatment
  • Resection, chemotherapy
Gross images

Contributed by Nicole K. Andeen, M.D. and Maria Tretiakova, M.D., Ph.D.

Solid white mass in renal pelvis

Microscopic (histologic) description
  • High grade neoplastic urothelial cells in tight small clusters and nests with retraction artifact, devoid of true fibrovascular cores
  • Lacunae are small, round, empty spaces that represent fixation artifact, not actual lymphovascular spaces, and not seen on frozen section (Adv Anat Pathol 2004;11:297)
  • Noninvasive pattern has slender micropapillae on surface of tumor
  • Micropapillary component may represent > 10% to < 90% of total tumor
    • Remainder may be classic urothelial carcinoma
  • Lymphovascular invasion nearly always present (in addition to the apparent invasion within lacunae)
Microscopic (histologic) images

Contributed by Nicole K. Andeen, M.D. and Maria Tretiakova, M.D., Ph.D.

Micropapillary urothelial carcinoma of renal pelvis with slender papillae on surface and characteristic tight clusters with retraction artifact, high grade nuclei



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Micropapillary processes

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CD31, CD34, D2-40

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CD31

Cytology description
  • Tightly packed three dimensional clusters of atypical cells with focal vacuolization and prominent nucleoli (Cytojournal 2013;10:4)
Cytology images

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Cytomorphology

Positive stains
Negative stains
Electron microscopy description
  • "Inside out" appearance, with stromal facing surface demonstrating apical secretory properties (microvilli) and lacking basement membrane, on an electron microscopy study in micropapillary breast carcinoma (Pathol Res Pract 1994;190:668)
Molecular / cytogenetics description
Differential diagnosis
  • Conventional urothelial carcinoma with retraction artifact: large, anastomosing or confluent nests support conventional UC
    • Immunohistochemistry is of limited diagnostic utility, with CA125 and HER2 showing high specificity but low sensitivity for micropapillary variant vs. conventional UC, and MUC1 showing high sensitivity but low specificity (Mod Pathol 2009;22:660)
  • Metastatic micropapillary carcinoma from another site: history and site specific markers, including lung, breast, ovary, colon, pancreas, salivary gland
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