Urachal carcinoma

Urachal carcinoma is an uncommon malignant tumour that arises from the urachus. Most urachal carcinomas are adenocarcinomas.

Urachal carcinoma
Diagnosis in short
Urachal carcinoma (right of image) and benign urothelium (left of image). H&E stain.
LM	atypical cells - usually gland forming, +/-mucinous component, +/-signet rings
Subtypes	enteric, mucinous, signet ring
LM DDx	adenocarcinoma of the urinary bladder, invasive urothelial carcinoma with glandular differentiation, metastatic adenocarcinoma
IHC	CK20 +ve, beta-catenin +ve (non-nuclear), p63 -ve, CK34betaE12 +ve
Grossing notes	partial cystectomy
Site	urachus, urinary bladder - specifically the dome
Signs	+/-hematuria
Prevalence	very rare
Prognosis	usually poor
Clin. DDx	other bladder tumours - esp. urothelial carcinoma

General

• Very rare~ 0.2% of bladder cancers.
• Often younger <55 years-old.
• Poor prognosis - especially for high Sheldon stage.

Clinical:

• Hematuria - classic presenation.

Treatment:

• Partial cystectomy +/- umbilectomy.

Gross

• Lesion must be in urachus or dome of urinary bladder.

Microscopic

Features of epithelial malignancy:

• Atypical (epithelial) cells.
  • May be signet ring cells.
• Usually gland forming, i.e. adenocarcinoma.
• +/-Mucinous component.

Features making it urothelial carcinoma (modified Sheldon criteria) - all required:

1. Located in bladder dome or anterior wall. †
2. Centered on bladder wall (as opposed to the mucosa).
3. No widespread cystitis cystica/glandularis outside of the bladder dome and anterior wall.
4. No known urothelial carcinoma elsewhere.

Notes:

• Gopalan et al.
• Adenocarcinoma of the urinary bladder.
• Invasive urothelial carcinoma with glandular differentiation.
• Metastatic adenocarcinoma/adenocarcinoma extending from another structure, e.g. colorectal adenocarcinoma.

Patterns

• Enteric - looks like colonic adenocarcinoma.
• Mucinous.
• Signet ring.

Note:

• Urachal carcinoma may be nonglandular.

Images

• 

  UC - very low mag. (WC)

• 

  UC - low mag. (WC)

• 

  UC - high mag. (WC)

IHC

Features:

• CK20 +ve.
• CK7 +ve/-ve.
• CK34betaE12 +ve/-ve.
• Beta-catenin -- usu cytoplasmic/membranous +ve.

Others:

• p63 -ve (+ve in only 3%).

UC versus CRC -- not absolute but useful:

• CK34betaE12 +ve in UC (-ve in CRC).
• Beta-catenin -ve nuclei in UC (+ve nuclei in CRC).

Sign out

• The diagnosis is a clinicopathologic diagnosis - one needs imaging to make it.
• May be staged with the Sheldon system.

Sheldon staging system

Staging as Sheldon et al.:

• pT1 - confined to urachal mucosa.
• pT2 - confined to the urachus.
• pT3a - extension into the bladder wall
• pT3b - extension into the abdominal wall.
• pT3c - structures other than the bladder.
• pT4a - metastasis to regional lymph nodes.
• pT4b - metastasis to distant sites.

See also

• Urinary bladder.
• Urothelium.
• Adenocarcinoma of the urinary bladder.