Breast

Other carcinoma subtypes, WHO classified

Mucinous


Editorial Board Member: Gary Tozbikian, M.D.
Editor-in-Chief: Debra L. Zynger, M.D.
Carissa LaBoy, M.D.
Kalliopi P. Siziopikou, M.D., Ph.D.

Topic Completed: 23 February 2021

Minor changes: 27 May 2021

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PubMed search: Mucinous carcinoma breast mass "free full text" [sb]

Carissa LaBoy, M.D.
Kalliopi P. Siziopikou, M.D., Ph.D.
Page views in 2020: 17,568
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Cite this page: LaBoy C, Siziopikou KP. Mucinous. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/breastmalignantmucinous.html. Accessed October 15th, 2021.
Definition / general
  • Breast neoplasm with mucinous component that comprises > 90% of tumor, usually with favorable prognosis
Essential features
  • Rare tumor occurring in older women
  • Epithelial clusters that lie within secreted mucin (type A) or large sheets of tumor cells with neuroendocrine features and mucin production (type B)
  • Mucinous component must be > 90% of tumor to be pure and have favorable prognosis
  • ER and PR hormone receptor positive and HER2 negative (luminal A subtype)
Terminology
  • Colloid carcinoma
  • Mucinoid carcinoma
  • Gelatinous carcinoma
  • Mucoid carcinoma
  • Mucinous adenocarcinoma
ICD coding
  • ICD-O: 8480/3 - mucinous adenocarcinoma
  • ICD-11: 2C60 - carcinoma of breast, specialized type
  • ICD-11: XH1S75 - mucinous adenocarcinoma
Epidemiology
  • < 5% of breast carcinomas have mucinous component; of these, only 2% are pure mucinous carcinoma
  • F > M, sixth through eighth decades
Sites
  • Most are unifocal and can occur in any quadrant
Pathophysiology
  • Occurs through ER positive pathway, though lack gains of 1q, loss of 16q and PIK3CA mutations, which are typical of low grade neoplasms (Breast 2020;49:87)
  • Lesions express hormone receptors while lacking HER2 and basal markers
Etiology
  • Multifactorial, with factors including hormones (early menarche, nulliparity or exogenous hormone use), genetics and diet
Clinical features
  • Imaging can vary from a well circumscribed mass (more likely to be pure) to an irregular, spiculated mass (more likely to have mixed mucinous component) (Breast 2020;49:87)
  • Due to potential circumscription seen on imaging, may be mistaken for benign process
Diagnosis
Radiology images

Contributed by Carissa LaBoy, M.D.
Mammogram of right breast

Mammogram of right breast

Ultrasound of left breast

Ultrasound of left breast

Mammogram of breast mass

Mammogram of breast mass

Mammogram of left breast

Mammogram of left breast

Prognostic factors
  • Prognosis dependent on extent of mucinous involvement; pure mucinous carcinoma has favorable prognosis with 10 year survival rate of 90.4% (Breast 2020;49:87)
  • No prognostic significance between type A and type B
  • Patients tend to have localized disease with low recurrence rate and rare involvement of axillary lymph nodes (Breast 2020;49:87)
  • Component of micropapillary pattern is associated with worse prognosis, with increased rate of lymph node metastasis (Breast J 2018;24:339)
  • Acellular mucin seen in postneoadjuvant chemotherapy specimens does not correlate with residual disease
  • Only when residual neoplastic epithelium is identified is the patient classified as partial response and staged with residual disease by measuring the extent of extracellular mucin (Histopathology 2018;72:965)
Case reports
Treatment
  • Surgical excision and adjuvant hormone therapy
  • Cases associated with worse prognosis, such as micropapillary variant, may warrant neoadjuvant chemotherapy (Breast J 2018;24:339, Histopathology 2018;72:965)
  • HER2 positivity is associated with tamoxifen resistance and should be treated with chemotherapy, anti-HER2 therapy and endocrine therapy via an aromatase inhibitor (Medicine (Baltimore) 2020;99:e20996)
Gross description
  • Well circumscribed mass of variable size (from < 1 cm to > 20 cm) with gelatinous cut surface
Gross images

Contributed by Mark R. Wick, M.D.
Pure Pure

Pure mucinous carcinoma



Images hosted on other servers:
Gross mass in the breast Gross mass in the breast

Gross mass in the breast

Microscopic (histologic) description
  • Clusters / nests of tumor cells with low or intermediate nuclear grade floating in pools of extracellular mucin
  • Mucin pools separated by fibrous septa with capillaries
  • Considered pure when mucinous component comprises > 90% of the tumor, which is associated with favorable prognosis
  • Otherwise, tumor is mixed (mucinous component comprises 50 - 90% of tumor) or has mucinous features (mucinous component comprises < 50% of tumor), both of which have less favorable prognosis
  • Capella type A: abundant extracellular mucin production with scattered small epithelial clusters, strips or cribriform structures floating in pools of mucin
  • Capella type B: large sheets of tumor cells with mucin production and neuroendocrine features
  • Micropapillary pattern
    • Clusters of tumor cells with intermediate to high grade nuclei, occasional hobnailing and reverse polarity; more likely to be HER2 positive, which in turn has a worse prognosis (more likely to have lymph vascular space invasion and metastasis to lymph nodes) (Breast J 2018;24:339)
    • PIK3CA and TP53 mutations more frequent with recurrent gains of 8q (Histopathology 2019;75:139)
Microscopic (histologic) images

Contributed by Carissa LaBoy, M.D.
Type A mucinous carcinoma

Type A mucinous carcinoma

Type A ER positive

Type A ER positive

Type A PR positive

Type A PR positive

Type A HER2 negative

Type A HER2 negative

Clusters in mucins pools

Clusters in mucin pools

Bland epithelial cell clusters

Bland epithelial cell clusters


Strips of epithelium

Strips of epithelium

Type B mucinous carcinoma

Type B mucinous carcinoma

Neuroendocrine features

Neuroendocrine
features



AFIP images and contributed by Mark R. Wick, M.D.
Grimelius staining denotes neuroendocrine differentiation Grimelius staining denotes neuroendocrine differentiation

Grimelius stain

Virtual slides

Images hosted on other servers:

Type A, tumor clusters

Type B, neuroendocrine features

Cytology description
  • Small to intermediate sized cohesive groups of epithelial cells with low grade nuclei floating within pools of extracellular mucin
  • Mucinous carcinoma type B displays neuroendocrine differentiation in discohesive clusters with plasmacytoid cells with low grade nuclei (Cytopathology 2016;27:193)
  • Low cellularity coupled with bland nuclear features and potentially scant background mucin can make the FNA diagnostically challenging (Arch Pathol Lab Med 2011;135:1533)
Cytology images

Images hosted on other servers:

FNA of mucinous carcinoma

Cytology smear of mucinous carcinoma

Cytospin preparation

Colloid carcinoma

Negative stains
Electron microscopy images

AFIP images

Cytoplasmic mucigen granules

Molecular / cytogenetics description
Videos

Review of mucinous carcinoma

Sample pathology report
  • Left breast, needle localized lumpectomy:
    • Invasive mucinous carcinoma, grade 1 (1+2+1), measuring 1.4 cm in greatest dimension (see synoptic report)
    • Margins negative with invasive carcinoma > 0.5 cm from all margins
Differential diagnosis
  • Mucocele-like lesion:
    • Ruptured cyst with detached strips of bland epithelium lined by myoepithelial cells floating within extravasated mucin
  • Mucinous cystadenocarcinoma:
  • Invasive micropapillary carcinoma:
    • Nests of tumor cells floating in spaces, mucin production absent
  • Metastasis:
    • Correlate with clinical and radiologic history, such as colorectal, lung and gynecologic
    • Expression profile dependent on origin
  • Solid papillary carcinoma:
    • Nests of cells with neuroendocrine features, fibrovascular cores and possible mucin production; may potentially be precursor to mucinous carcinoma
  • Invasive ductal carcinoma, no special type, with mucinous features:
    • Histologic features are those of pure mucinous carcinoma but mucinous component does not fulfill > 90% criteria
    • May be initial diagnosis on core needle biopsy for pure mucinous carcinoma
    • Due to limited material sampled on core needle biopsy, amount of mucinous component is more reliably assessed on excision specimen
Board review style question #1

What is the most likely hormone receptor profile of the above breast lesion?

  1. ER+, PR+, HER2-
  2. ER-, PR-, HER2-
  3. ER+, PR+, HER2+
  4. ER-, PR+, HER2+
Board review style answer #1
A. ER+, PR+, HER2-

Mucinous carcinomas are ER+, PR+ and largely HER2-, making them a luminal A lesion, which is associated with a favorable prognosis.

Comment Here

Reference: Breast - Mucinous
Board review style question #2

What percentage of a breast carcinoma must have a mucinous component to be considered pure mucinous carcinoma?

  1. 75%
  2. 50 - 90%
  3. > 90%
  4. 30%
Board review style answer #2
C. > 90%

To be considered a pure mucinous carcinoma with a favorable prognosis, the mucinous component must comprise > 90% of a breast carcinoma. If it comprises 50 - 90% of the tumor, it is termed mixed. If the mucinous component is < 50%, the tumor is termed invasive ductal carcinoma with mucinous features. The latter two diagnoses do not have as favorable a diagnosis.

Comment Here

Reference: Mucinous carcinoma
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