Mucinous breast carcinoma

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Mucinous breast carcinoma
Diagnosis in short

Mucinous breast carcinoma. H&E stain.

LM malignant mucin producing glands - where mucinous component must comprise >90% of the tumour, tumour cells should float in the mucin, glands typically have irregular edges, +/-vessels within the mucin pools
LM DDx other type of breast cancer with a mucinous component (very common), other mucinous tumours
IHC ER +ve, PR +ve, HER2 -ve
Gross pale, glistening, jelly-like appearance
Grossing notes breast grossing
Staging breast cancer staging
Site breast - see invasive breast cancer

Prevalence uncommon
Prognosis good compared to the usual ductal carcinoma
Clin. DDx other breast tumours

Mucinous breast carcinoma is an uncommon form of breast cancer that has a good prognosis compared to the common invasive ductal carcinoma.

It is also known as mucinous carcinoma of the breast, and colloid carcinoma of the breast.

General

  • Rare.
  • 2% of invasive breast carcinomas.
  • Good prognosis.[1]
  • Usually older women.

Gross

  • Pale, glistening, jelly-like appearance.
  • Well-circumscribed.

Image:

Microscopic

Features:

  • Malignant mucin producing glands.
    • Mucinous component must comprise >90% of the tumour - required for diagnosis.[2]
    • Small clusters of cells should float in the mucin - key feature.
    • Glands typically have irregular edges.
    • +/-Vessels within the mucin pools.
  • Subtypes [3]
    • Mucinous A (or paucicellular) - more mucin
    • Mucinous B (or hypercellular) - less mucin and neuroendocrine differentiation and argyrophilia

DDx:

  • DCIS with a mucinous component.
    • Mucin has a homogenous appearance, mucin lacks vascularization, mucin pools have a regular border.
  • Invasive ductal carcinoma of the breast with a mucinous component - more common than mucinous breast carcinoma. Any 'no special type' component imparts a worse prognosis so the diagnosis 'mucinous carcinoma' is reserved for tumours with close to pure mucinous features.

Note:

  • The amount of mucinous component to call mucinous carcinoma varies by anatomical site.
  • A breast core biopsy that show any degree of mucinous change is an indication for excision to exclude mucinous carcinoma.[4]
  • Size and margins are assessed from edge of mucin, even if it does not contain epithelial cells
  • These tumors can be very difficult to assess lymphovascular invasion. Look for tumour cells in areas where lymphatics are expected ie. tumour in arc-shape around vascular bundle

Images

IHC

  • ER +ve.
  • PR +ve.
  • HER2 -ve.

See also

References

  1. Barkley, CR.; Ligibel, JA.; Wong, JS.; Lipsitz, S.; Smith, BL.; Golshan, M. (Oct 2008). "Mucinous breast carcinoma: a large contemporary series.". Am J Surg 196 (4): 549-51. doi:10.1016/j.amjsurg.2008.06.013. PMID 18809061.
  2. Dogan, E.; Aksoy, S.; Dizdar, O.; Arslan, C.; Dede, DS.; Ozisik, Y.; Altundag, K.. "Pure mucinous carcinoma of the breast: a single center experience.". J BUON 16 (3): 565-7. PMID 22006768.
  3. Weigelt, B.; Geyer, FC.; Horlings, HM.; Kreike, B.; Halfwerk, H.; Reis-Filho, JS. (Nov 2009). "Mucinous and neuroendocrine breast carcinomas are transcriptionally distinct from invasive ductal carcinomas of no special type.". Mod Pathol 22 (11): 1401-14. doi:10.1038/modpathol.2009.112. PMID 19633645.
  4. Jacobs, TW.; Connolly, JL.; Schnitt, SJ. (Sep 2002). "Nonmalignant lesions in breast core needle biopsies: to excise or not to excise?". Am J Surg Pathol 26 (9): 1095-110. PMID 12218567.