Bladder, ureter & renal pelvis

Urothelial carcinoma - invasive

Micropapillary



Last author update: 26 October 2022
Last staff update: 26 October 2022

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PubMed Search: Micropapillary urothelial carcinoma

Timothy Isaac Miller, M.D., M.A.
Maria Tretiakova, M.D., Ph.D.
Page views in 2021: 3,366
Page views in 2022 to date: 3,831
Cite this page: Miller TI, Tretiakova M. Micropapillary. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/kidneytumormalignanturothelialcarcinomasubtypesmicropap.html. Accessed December 6th, 2022.
Definition / general
  • Aggressive histologic subtype of urothelial carcinoma (UC) comprised of small papillary clusters of neoplastic cells within lacunae and without fibrovascular cores (Am J Surg Pathol 1994;18:1224)
  • If noninvasive, appears as slender, delicate filiform processes on surface (Am J Surg Pathol 1994;18:1224)
Essential features
  • Uncommon histologic subtype of UC with micropapillary architecture lacking fibrovascular cores
  • Multiple clusters of tumor cells with peripherally oriented nuclei sharing cleft-like spaces or lacunae, often resembling vascular invasion
  • More likely to be diagnosed at an advanced stage compared with conventional UC, conferring a poorer prognosis
  • If micropapillary urothelial carcinoma (MPUC) is seen on biopsy, it is highly associated with muscularis propria invasive disease
Terminology
  • Micropapillary urothelial carcinoma (MPUC)
  • Conventional urothelial carcinoma (CUC)
ICD coding
  • ICD-O: 8120/3 - transitional cell carcinoma, NOS
Epidemiology
Sites
  • Bladder
  • Renal pelvis
  • Ureter
Pathophysiology
Clinical features
  • Most common presenting symptom: painless gross hematuria
  • Other urinary symptoms: dysuria, urgency, frequency, painful micturition
  • More likely to present at advanced stage with extravesical disease and lymph node metastases (Urol Oncol 2019;37:48, Urol Oncol 2014;32:110, World J Urol 2012;30:801)
    • Meta analysis: at diagnosis, median rate of muscle invasive disease is 41%, lymph node involvement is 12.5% and metastasis is 5% (Eur Urol 2019;75:649)
Diagnosis
  • Clinical symptoms prompt cystoscopy, which then results in a transurethral biopsy or resection of tumor
  • Imaging may show mass in bladder wall or diffuse bladder wall thickening, which results in cystoscopy with biopsy
Laboratory
Radiology description
Radiology images

Images hosted on other servers:

CT with bladder tumor invading the left ureteral orifice

CT with tumor in right posterolateral bladder wall

Prognostic factors
Case reports
  • 70 year old man presented with hematuria and found to have a bladder tumor involving the dome and extending to the perivesical fat (Can Urol Assoc J 2008;2:540)
  • 70 year old woman hospitalized for dyspnea with pulmonary microangiopathy from metastases and at autopsy, found to have MPUC in the bladder (Intern Med 2021;60:2843)
  • 73 year old woman presented with hematuria and found to have a mass of the left renal pelvis (Med Sci Monit 2007;13:CS47)
  • 74 year old man hospitalized for hematuria found to have multifocal papillary bladder tumors with histology showing both micropapillary and plasmacytoid urothelial carcinoma (Diagn Cytopathol 2016;44:124)
  • 82 year old man with end stage kidney disease on hemodialysis and found to have a sessile papillary tumor on the left bladder wall (Case Rep Oncol 2022;15:462)
Treatment
  • Transurethral resection of bladder cancer (TURB) with intravesical bacillus Calmette-Guérin (BCG) may not be as effective (Eur Urol Focus 2020;6:653)
  • Early radial cystectomy (RC) may improve survival (J Urol 2015;193:1129)
  • Many patients are immediately upstaged at RC compared with TURB stage, suggesting one reason why RC is the preferred option (Pathology 2010;42:650)
  • Role of neoadjuvant chemotherapy before RC is not clear, although it is associated with pathological downstaging, it does not show increased overall survival (Eur Urol 2019;75:649)
Gross description
Microscopic (histologic) description
  • Small nests of tumor cells with surrounding lacunar (empty) space and without fibrovascular cores (Eur Urol Focus 2020;6:653)
    • Presence of multiple nests in one lacunae is a classic feature and may be the most helpful feature in making the diagnosis (Am J Surg Pathol 2010;34:1367)
    • Must be careful not to confuse lacunae with lymphovascular invasion; lacunae may be lined with flattened endothelial type cells that are not lymphovascular in origin
  • Epithelial ring forms and intracytoplasmic vacuolization may also be present (Eur Urol Focus 2020;6:653)
  • Stromal reaction to tumor cells may be absent (Mod Pathol 2009;22:S96)
  • Usually has high nuclear grade (Mod Pathol 2009;22:S96)
Microscopic (histologic) images

Contributed by Timothy Isaac Miller, M.D., M.A. and Maria Tretiakova, M.D., Ph.D.

Classic features

Micropapillary
and conventional
urothelial
carcinoma

Multiple nests throughout stroma

Epithelial ring morphology

Ring forms and intracytoplasmic vacuolization

Numerous nests in large lacunae

Cytology description
Cytology images

Images hosted on other servers:
Missing Image Missing Image

Cohesive clusters in a 3 dimensional arrangement

Molecular / cytogenetics description
Videos

Bladder urothelial carcinoma

Sample pathology report
  • Bladder, transurethral resection:
    • Urothelial carcinoma, high grade
      • Histologic component: micropapillary (90%)
      • Adjacent flat carcinoma in situ: absent
      • Angiolymphatic invasion: absent
      • Muscularis propria: present, invaded by carcinoma
      • Depth of invasion: invasive of muscularis propria (pT2)
  • Bladder, cystectomy:
    • Invasive high grade urothelial carcinoma, micropapillary subtype (see synoptic report)
Differential diagnosis
Board review style question #1

Which of the following is true regarding the histologic subtype of urothelial carcinoma shown above?

  1. Fibrovascular cores should be present in order to call it this histologic subtype
  2. Neoadjuvant chemotherapy is the standard of care for this subtype
  3. Patients are more likely to have better outcomes if this subtype represents > 10% of the tumor content
  4. Patients are more likely to present at an advanced stage compared with conventional urothelial carcinoma
  5. There is no concordant in situ histologic correlation to this subtype
Board review style answer #1
D. Patients are more likely to present at an advanced stage compared with conventional urothelial carcinoma

The image above is the micropapillary histologic subtype of urothelial carcinoma. When micropapillary histology is found on biopsy, patients are more likely to already have muscularis propria invasion, lymph node metastasis and extravesicular extension, overall conferring a worse prognosis and why it is important to report this subtype. The role of neoadjuvant therapy before radical cystectomy in micropapillary cases is not clear and may not actually improve overall survival (choice B is incorrect). Fibrovascular cores should not be present within the clusters of cells (choice A is incorrect). If the micropapillary histology comprises > 10% of the tumor, then patients are more likely to have worse, not better outcomes (choice C is incorrect). There is an in situ micropapillary subtype that will look like slender filiform processes (choice E is incorrect) (Urol Oncol 2019;37:48, Urol Oncol 2014;32:110, World J Urol 2012;30:801, Eur Urol 2019;75:649, Histopathology 2004;45:55, Am J Surg Pathol 1994;18:1224).

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