Low-grade papillary urothelial carcinoma

Low-grade papillary urothelial carcinoma
Diagnosis in short
Low-grade papillary urothelial carcinoma. H&E stain.
LM	papillae (fibrovascular cores covered by urothelium) -- usually with fusion and branching, small nuclei (~3x a resting lymphocyte), +/-invasion into the lamina propria (rare), +/-mitoses (uncommon)
LM DDx	PUNLMP, urothelial papilloma, inverted papilloma, high-grade papillary urothelial carcinoma
IHC	Ki-67 low (<25% of cells)
Gross	exophytic lesion, frond-like appearance, friable
Site	urothelium
Syndromes	Lynch syndrome
Signs	hematuria
Prevalence	very common
Prognosis	very good
Clin. DDx	high-grade papillary urothelial carcinoma, urothelial papilloma

Low-grade papillary urothelial carcinoma, abbreviated LGPUC, is a very common indolent form of cancer that arises from the urothelium.

It is also known as low-grade papillary urothelial cell carcinoma, abbreviated LGPUCC.

General

• Very common.
• Very good prognosis - if it is non-invasive.
• Usually non-invasive.

Note:

• Invasive low-grade UCC is:
  • ~75% nested variant of urothelial carcinoma.
  • ~25: low-grade papillary urothelial carcinoma.

Gross

• Exophytic lesion.
• Frond-like appearance.

Microscopic

Features:

• Papillae = fibrovascular cores covered by urothelium.
  • Usually with fusion of papillae and branching of papillae.
• Small nuclei (~3x a resting lymphocyte).
• +/-Invasion into the lamina propria (rare).
• Rare mitoses.
  • Usually difficult to find.
  • Basal location.

Criteria for invasion (mnemonic PISS-R):

• Stromal reaction.
• Infiltrating single cells.
• Small nests.
• Retraction artifact.
• Paradoxical differentiation.

Note:

• Nuclei slightly larger than in PUNLMPs.
• The presence/absence of muscle should be commented on in biopsy specimens.
• Adipose tissue may be seen in the lamina propria; tumour adjacent to adipose tissue on a biopsy does not imply invasion deep to the muscularis propria.

DDx:

• PUNLMP.
• High grade papillary urothelial carcinoma.
  • Often under-diagnosed (~15% in one series) when reassessed by experts.
  • The three most predictive features of high-grade are architectural complexity, nuclear size variation, and absence of umbrella cells.
  • Stanford criteria has a 5% rule -- if the high-grade component is <5% it is low-grade.
• Inverted urothelial papilloma - often have peripheral palisading.
• Urothelial papilloma.

Image

• 

  LGPUC - intermed. mag.

• 

  LGPUC - high mag.

• 

  LGPUC - high mag.

IHC

• Ki-67:
  • Rajcani et al.: <25% of tumour cells for low-grade versus >50% tumour cell for high-grade.
  • Pich et al.: 11%/17% for G1/G2 versus 34% for G3.
  • Mai et al. suggest there is overlap: 10-30% for low-grade versus 20-50% for high-grade.

Molecular

Molecular changes:

• FGFR3
• HRAS
• Loss of heterozygosity - chromosome 9.

Note:

• Not currently used diagnostically.

Sign out

 URINARY BLADDER LESION ("TUMOUR"), TRANSURETHRAL RESECTION:
- LOW-GRADE PAPILLARY UROTHELIAL CARCINOMA.
-- NEGATIVE FOR LAMINA PROPRIA INVASION.
- NO MUSCULARIS PROPRIA IDENTIFIED.

Muscularis propria present

URINARY BLADDER LESION ("TUMOUR"), TRANSURETHRAL RESECTION:
- LOW-GRADE PAPILLARY UROTHELIAL CARCINOMA.
-- NEGATIVE FOR LAMINA PROPRIA INVASION.
- BENIGN MUSCULARIS PROPRIA PRESENT.

Micro

The sections show urothelial mucosa with a tumour with fibrovascular cores. The nuclei are of uniform size (2-3 times a resting lymphocytes). Rare foci of degenerative cells are seen. The papillary structures are thick and appear to compress the lamina propria. Rare mitotic figures are identified. No atypical mitoses are apparent. No lamina propria invasion is identified. No muscularis propria is identified.

See also

• Urothelium.
• Urinary bladder.
• Genitourinary pathology.