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Breast pathology — benign lesions, ductal and lobular carcinoma and molecular subtypes
Breast lesions are ranked by the risk they carry — non-proliferative, proliferative without atypia and proliferative with atypia — and invasive carcinoma is described by type (mostly "no special type" or lobular), Nottingham grade, and markers (ER, PR, HER2, Ki-67) that define a molecular subtype and treatment.
Why it matters in the exam
The bank asks about risk, the difference between ductal and lobular and the subtypes. Non-proliferative changes (cysts, fibrosis) do not raise risk significantly; proliferative lesions without atypia (usual hyperplasia, sclerosing adenosis, papilloma) raise it about 1.5–2 times; atypical hyperplasia, ductal or lobular, raises it about 4–5 times. Fibroadenoma is a benign tumour of stroma and epithelium; a phyllodes tumour differs from it by stromal overgrowth and a "leaf-like" architecture, and can be benign, borderline or malignant.
Carcinoma of no special type (NST, "ductal") is the most common. Invasive lobular carcinoma is characterised by loss of E-cadherin (CDH1), small cells invading in single files and a diffuse pattern, tends to be bilateral and multifocal, and metastasises distinctively to the peritoneum, gastrointestinal tract and ovaries. Special types with good prognosis: tubular and mucinous. Nottingham grade sums three components — tubule formation, nuclear pleomorphism and mitotic count — each 1–3 points: total 3–5 grade 1, 6–7 grade 2, 8–9 grade 3.
Molecular subtypes: luminal A (ER positive, HER2 negative, low Ki-67) with good prognosis; luminal B; HER2-enriched; and triple-negative (basal-like). Tumours in BRCA1 carriers are mostly triple-negative, and in BRCA2 carriers mostly luminal. Pathological complete response to neoadjuvant chemotherapy is more common in triple-negative and HER2-amplified tumours, and early recurrence — in the first two years — is also especially common in triple-negative tumours. Inflammatory carcinoma is defined clinically, and pathology shows tumour emboli in dermal lymphatics.
Key points
- Risk: non-proliferative — almost none; proliferative — 1.5–2 times; atypical — 4–5 times.
- Lobular: loss of E-cadherin, single files, bilateral.
- Nottingham: tubules, nuclei, mitoses; 3–9 points.
- BRCA1 — triple-negative; BRCA2 — luminal.
- Complete response and early recurrence are common in triple-negative.
Summary table
| Lesion or tumour | Risk or feature | Key finding | Note |
|---|---|---|---|
| Non-proliferative | No significant increase | Cysts, fibrosis | — |
| Proliferative without atypia | 1.5–2 times | Usual hyperplasia, sclerosing adenosis | — |
| Atypical hyperplasia | 4–5 times | ADH or ALH | Follow-up and risk reduction |
| Lobular carcinoma | Loss of E-cadherin | Single files, bilateral | Metastases to peritoneum and ovaries |
| Triple-negative | BRCA1, aggressive | ER, PR and HER2 negative | Complete response common; early recurrence |
Free exam questions
מה נכון לגבי BRCA ב סרטן השד? (the question as examined, in Hebrew)
- א. מוטציות ב BRCA-1, BRCA-2 אחראיות על 20% מכלל המקרים של סרטן שד
- ב. הסוג ההיסטולוגי של סרטן שד השכיח ביותר בנשאיות של הגן ל BRCA הוא tubular carcinoma
- ג. נשאיות של המוטציה ל BRCA-2 נוטות לפתח גידולים חיוביים ל ER יותר מנשאיות למוטציה ל BRCA-1
- ד. מוטציה ל BRCA-1 מעלה את הסיכו ן לסרטן השד פי 2
בת 70 עם סרטן שד גרורתי מסוג triple negative , PDL1-negative . מה היתרון במתן משלב של תרוופות כימותרפיה לעומת תרופה יחידה ? (the question as examined, in Hebrew)
- א. משפר overall survival
- ב. משפר response rate
- ג. משפר איכות חיים
- ד. אין יתרון
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Sources
- WHO Classification of Tumours: Breast Tumours, 5th edition (2019) — Benign epithelial proliferations; invasive carcinoma
- CAP Protocol for the Examination of Resection Specimens from Patients with Invasive Carcinoma of the Breast, 2024 — Nottingham grade and biomarker reporting
- Robbins and Cotran Pathologic Basis of Disease, 10th edition (2021) — The breast
Sources are given for further reading; the text is written afresh and not copied from them.
Reviewed by the Examqo AI Professor · 2026-11-06. The text may contain errors; when in doubt, check the source.
See also: BI-RADS: lexicon and assessment in mammography and breast ultrasound