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 presentation.

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 urachal 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. (based on Sheldon) suggests the following additional/more restrictive criteria:
  • Only the dome is allowed. †
  • Lesion should be sharply demarcated from the urothelium of the urinary bladder.
  • Urachal remnants should be present in the tumour.

DDx:

• Adenocarcinoma of the urinary bladder.
• Invasive urothelial carcinoma with glandular differentiation.
• Metastatic adenocarcinoma/adenocarcinoma extending from another structure, e.g. colorectal adenocarcinoma.
• Villous adenoma of the urachus - non-invasive.

Patterns

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

Note:

• Urachal carcinoma may be nonglandular.

Images

• 

  UC - very low mag. (WC/Nephron)

• 

  UC - low mag. (WC/Nephron)

• 

  UC - intermed mag. (WC/Nephron)

• 

  UC - high mag. (WC/Nephron)

• 

  UC - very high mag. (WC/Nephron)

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

Mass, Urachus, Resection:
     - ADENOCARCINOMA, consistent with urachal primary, see comment.
     -- Margins clear.

Comment: 
The sections show malignant cells within the perivesicular soft tissue arranged in nests and glands with necrosis. The lesion center is within the bladder wall, rather than at the mucosa. The sampled bladder mucosa is within normal limits. 

The tumour stains as follows:
POSITIVE: CDX2 (focal, moderate nuclear), CK20 (focal, moderate membranous).
NEGATIVE: CK7, p63, CK5/6, GATA3, beta-catenin (membranous only, nuclei negative). 

The histomorphology, immunoprofile and imaging are compatible with a primary urachal adenocarcinoma. 

The morphology and immunoprofile of urachal adenocarcinoma overlaps with primary adenocarcinoma of the bladder and somewhat with colorectal adenocarcinoma. Primary adenocarcinoma of the bladder is unlikely as the sampled urothelium is benign, the lesion is centered within the wall and no history of bladder tumours was found.  Metastatic colorectal cancer seems unlikely from the clinical information available.

The CAP bladder synoptic is not applicable to urachal carcinoma. 

In the context of the "Sheldon Staging System" for urachal carcinoma, this case would be pT3a.

Note:

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

Sheldon staging system

Staging as per 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.