Invasive breast carcinoma: special types
- Lesion
Some breast cancers have a distinctive pattern that predicts their behaviour: some are kinder than usual, others spread in unusual ways.
What it is
About a quarter of invasive breast carcinomas show a special histologic pattern that carries prognostic meaning. Invasive lobular carcinoma, the most common special type, grows in single files because it has lost E-cadherin and spreads to unusual sites. Tubular and mucinous carcinomas are ER-positive and have an excellent prognosis. The medullary pattern, now grouped with tumours rich in lymphocytes, is triple-negative but does better than its grade suggests. Metaplastic and micropapillary carcinomas behave aggressively, while secretory and adenoid cystic carcinomas are rare and indolent.
Structure
- Lobular: small uniform cells in single files and concentric rings around ducts; stroma little altered.
- Mucinous: lakes of mucin occupying most of the tumour with small floating nests.
- Micropapillary: hollow clusters of cells with inside-out polarity in empty spaces.
- Apocrine: large cells with abundant granular pink cytoplasm, androgen receptor positive.
Step by step
- Loss of E-cadherin (CDH1) frees lobular cells from each other, so they infiltrate one by one.
- Single discohesive cells form little desmoplasia, so the tumour may be felt as thickening rather than a lump.
- Other special types reflect particular programs: abundant mucin secretion, well-formed tubules, or epithelial-mesenchymal transition in metaplastic carcinoma.
- Fusion genes drive rare indolent types: ETV6-NTRK3 in secretory carcinoma, MYB-NFIB in adenoid cystic carcinoma.
Special types of invasive breast carcinoma
| Type | Key feature | Receptors | Prognosis |
|---|---|---|---|
| Invasive lobular | Single files, E-cadherin loss | ER-positive | Similar to no special type; unusual metastatic sites |
| Tubular | Angulated single-layer tubules | ER-positive | Excellent |
| Mucinous | Cells floating in mucin | ER-positive | Good |
| Medullary pattern (lymphocyte-rich) | Syncytial sheets, pushing border, lymphocytes | Triple-negative | Better than expected for grade |
| Metaplastic | Squamous or mesenchymal elements | Triple-negative | Poor |
| Invasive micropapillary | Inside-out clusters in clear spaces | Usually ER-positive | Frequent node metastases |
| Secretory | Secretions, ETV6-NTRK3 fusion | Triple-negative | Good |
| Adenoid cystic | Cribriform glands, MYB-NFIB fusion | Triple-negative | Excellent |
Markers
- E-cadherin (negative in lobular)
- Androgen receptor (apocrine)
- Pan-TRK (secretory)
- MYB (adenoid cystic)
Clinical notes
- Lobular carcinoma can present with peritoneal, ovarian, gastric or meningeal metastases years after the primary.
- Recognising favourable types such as tubular and mucinous carcinoma can spare some patients aggressive treatment.
- Triple-negative is not always aggressive: secretory and adenoid cystic carcinomas are exceptions.
Test yourself
Think of the answer, then tap the question to see it.
Why does invasive lobular carcinoma grow in single files?
Its cells have lost E-cadherin, so they do not adhere to one another.
Which special types have an excellent prognosis?
Tubular, mucinous, secretory and adenoid cystic carcinomas.
To which unusual sites does lobular carcinoma metastasise?
Peritoneum, retroperitoneum, leptomeninges, gastrointestinal tract, ovaries, uterus and bone marrow.
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Educational content on the mechanisms of disease; not a diagnostic or treatment guide and no substitute for a health professional's advice. No doses are given.
Sources: Breast Cancer Treatment (PDQ®)–Health Professional Version (National Cancer Institute, 2026).
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Representative model, for educational purposes only.