Bladder, ureter & renal pelvis
Urothelial carcinoma - invasive
Micropapillary
Topic Completed: 1 September 2015
Minor changes: 11 November 2021
Copyright: 2003-2021, PathologyOutlines.com, Inc.
PubMed Search: Urothelial carcinoma of renal pelvis micropapillary
Related Topic: Urothelial carcinoma of renal pelvis
Table of Contents
Definition / general | Essential features | Epidemiology | Sites | Pathophysiology | Clinical features | Prognostic factors | Case reports | Treatment | Gross images | Microscopic (histologic) description | Microscopic (histologic) images | Cytology description | Cytology images | Positive stains | Negative stains | Electron microscopy description | Molecular / cytogenetics description | Differential diagnosis | Additional referencesCite this page: Andeen NK, Tretiakova M. Micropapillary. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/kidneytumormalignanturothelialcarcinomasubtypesmicropap.html. Accessed December 6th, 2021.
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
- Rare variant, seen in 2.3 to 3.7% of high grade urothelial carcinomas of renal pelvis (Mod Pathol 2006;19:494, Arch Pathol Lab Med 2009;133:62, Am J Clin Pathol 2006;126:86)
- Male predominance
- Mean age 64 years (range 22 - 92 years)
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 or other mechanisms (Am J Clin Pathol 2004;121:857, 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
- Percentage of micropapillary component is a negative prognostic factor (Mod Pathol 2009;22:S96)
Case reports
- 68 year old man with papillary transitional cell carcinoma (Am J Surg Pathol 1996;20:125)
- 73 year old woman with micropapillary urothelial carcinoma of the renal pelvis (Med Sci Monit 2007;13:CS47)
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)
- May be demonstrated with lymphovascular markers: CD31, factor VIII, D2-40 (Arch Pathol Lab Med 2012;136:635)
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
Cytology description
- Tightly packed three dimensional clusters of atypical cells with focal vacuolization and prominent nucleoli (Cytojournal 2013;10:4)
Cytology images
Images hosted on other servers:
Cytomorphology
Positive stains
- CK7 (100%), CK20 (90%), MUC1 / EMA (band-like expression on stroma facing surface) (100%), CEA (65%), CD125 (35%) (Arch Pathol Lab Med 2007;131:1244)
- HER2 and EGFR (75%) (Target Oncol 2015;10:355)
- Uroplakin II & III, GATA3 (100%) (Hum Pathol 2014;45:1824)
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
- Despite aggressive behavior, does not appear to have p53 abnormalities (J Urol 2000;163:748)
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 versus 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
Additional references
