Mucinous carcinoma

Mucinous carcinoma, also mucinous adenocarcinoma, is an epithelial neoplasm that produces mucin. Mucinous carcinoma can arise in a number of sites. It is also known as colloid carcinoma.

General

Prognostic significance dependent on the primary site:

• Breast mucinous carcinoma has a better prognosis.
• Colorectal mucinous carcinoma has a worse prognosis.

Specific sites

• Ovarian mucinous adenocarcinoma.
• Mucinous prostate carcinoma.
• Mucinous breast carcinoma.

Gross

• Gelatinous-like material.
  • May have a consistency similar to Jello.

Image:

• Mucinous adenocarcinoma of the lung (flickr.com).
• Ovarian mucinous cystadenocarcinoma (flickr.com/euthman).

Microscopic

Features:

1. Mucin - amphormous whispy or cream material.
2. Cytologically atypical cells within the mucin.
3. +/-Tumour without mucin.
   • Maximum amount acceptable depends on the primary site (see proportion of mucin section below).

Note:

• Mucin alone -- should prompt a search for atypical cells, i.e. levels should be done.

DDx:

• Benign mucocele.
• Mucin extravasation - no malignant cells present.
• Adenoma with pseudoinvasion (pseudocarcinoma).
• Adenocarcinoma with mucinous features - see proportion of mucin section.
• Other myxoid tumours - has an exhaustive long DDx.

Images

• 

  Colonic mucinous adenocarcinoma - very low mag. (WC/Nephron)

• 

  Colonic mucinous adenocarcinoma - low mag. (WC/Nephron)

www:

• Mucinous tumours of the ovary - several images (flickr.com).

Proportion of mucin

The criteria for diagnosing "mucinous carcinoma" varies by the anatomical site:

• Mucinous prostate carcinoma: > 25% of the tumour.
• Mucinous colorectal carcinoma: > 50% of the tumour.
• Mucinous gastric carcinoma: > 50% of the tumour.
• Mucinous breast carcinoma: > 90% of the tumour.
  • One source suggests: > 50% of the tumour.

Molecular

• May be associated with a KRAS mutation.

IHC

Can be used to suggest a primary site:

• Upper GI tract: CK7 +ve (38/41 cases), CDX2 -ve (4 +ve/41 cases).
• Lower GI tract: CDX2 +ve (42/42 cases), CK20 +ve (41/42 cases), CK7 -ve (8 +ve/42 cases) positive cases usu. in rectum/anus.
• Breast: CK7 +ve (18/18 cases), ER +ve (16/18 cases).
• Lung: CK7 +ve (16/16 cases).
• Gynecologic: CK7 +ve (25/27 cases).

Sign out

In biopsies:

• Adenocarcinoma with a mucinous component is probably the most objective way to sign out a case, if the primary site is not firmly established and a non-mucinous component is present.

OMENTUM, CORE BIOPSY:
- METASTATIC MUCINOUS ADENOCARCINOMA, SEE COMMENT.

COMMENT:
The tumour cells stain as follows:
POSITIVE: CK20, CDX2.
NEGATIVE: CK7.

The immunostains are suggestive of a lower gastrointestinal tract primary. Radiologic 
and endoscopic correlation is suggested.

See also

• Renal mucinous tubular and spindle cell carcinoma.
• Myxoid tumours.