01Core principlesThe concepts and mechanisms needed to understand the subject.
Breast-cancer risk arises from interaction between ageing breast tissue, inherited susceptibility, previous histological changes, endogenous hormone exposure and modifiable exposures. One relative with late-onset disease may contribute less evidence of a high-penetrance syndrome than several early, bilateral or related cancers across generations. Conversely, a quiet paternal pedigree with few women provides little information and should not be called negative. Verification of diagnoses strengthens any calculation.
Risk tools formalise information that unaided judgement may weigh inconsistently. BOADICEA-based tools estimate breast and ovarian risks and carrier probabilities using detailed family and genetic data; the Manchester system estimates pathogenic-variant probability from cancer patterns. NICE asks services to use a method with demonstrated calibration and discrimination. Every output needs its question, population, time horizon and limitations stated before it is used to change surveillance or preventive care.
Key points
- Age is a major breast-cancer risk factor. Family pattern, prior high-risk breast lesions, breast density, reproductive-hormonal exposure, alcohol and postmenopausal excess weight can modify an individual estimate.
- Take a three-generation maternal and paternal history, recording cancer site, age at diagnosis, bilateral or multiple primaries, sex at birth where relevant, ancestry, pathology and genetic results.
- Paternal transmission matters because autosomal dominant susceptibility variants can pass through any parent; a small family or few female relatives can make the pedigree look falsely reassuring.
- NICE categories use lifetime risk from age 20: below 17% near-population, 17% or more but below 30% moderate, and 30% or more high risk; ages 40–50 also use 10-year thresholds below 3%, 3–8% and above 8%.
- Validated models combine different variables and answer different questions. A future breast-cancer risk model is not interchangeable with a BRCA carrier-probability model.
- Communicate absolute risk over a stated time horizon and acknowledge uncertainty. The estimate guides genetics, surveillance and prevention discussion; it does not diagnose cancer or eliminate symptom assessment.
02Mechanisms and patternsImportant relationships and how to distinguish them.
Young diagnoses, bilateral primaries, ovarian cancer, male breast cancer, pancreatic or prostate cancer, multiple affected generations and certain ancestries increase concern.
Atypical hyperplasia, lobular neoplasia, prior DCIS and dense tissue can increase future risk and may alter model inputs or surveillance.
Early menarche, later menopause, nulliparity or later first birth, some combined HRT exposure and recent hormonal contraception can modestly affect risk.
Alcohol, postmenopausal excess weight, smoking and low physical activity contribute at population level, but counselling should avoid blame or false guarantees.
03Interpreting evidenceInformation, measurements and their limitations.
Consider the information, its meaning and its limitations before deciding what follows.
- 01
Three-generation pedigree - Why
- Capture maternal and paternal cancer patterns with ages, primary sites and links between relatives.
- Interpretation and limitations
- Verify key diagnoses where possible. Absence of known cancer in a small or male-dominated family is less informative than a large well-documented pedigree.
- 02
Formal future-risk model - Why
- Estimate breast-cancer probability over a defined period to support surveillance and preventive decisions.
- Interpretation and limitations
- Enter current age, family structure, reproductive factors, breast history and genetic data accurately. State which model and horizon produced the number.
- 03
Carrier-probability calculation - Why
- Estimate the chance of a pathogenic susceptibility variant and inform genetics referral or testing.
- Interpretation and limitations
- NICE cites methods with demonstrated performance such as BOADICEA and the Manchester scoring system. This probability is distinct from lifetime cancer risk.
- 04
Source-record verification - Why
- Confirm reported cancer sites, ages and prior genetic results before irreversible decisions.
- Interpretation and limitations
- Pathology or genetics reports can distinguish primary ovarian cancer from metastasis and a pathogenic variant from an uncertain finding.
04Applied reasoningWorked examples connecting principles to decisions.
01Worked case: classify familial riskConvert a family story into an auditable estimateIllustrative worked example: a 38-year-old reports breast cancer in her mother at 42 and ovarian cancer in a paternal aunt at 49; the initial appointment has no source reports.+
- 1The clinician recorded a three-generation pedigree across both parental lineages and obtained consent to request the key pathology and genetics records.
- 2The records subsequently confirmed the mother's invasive breast primary and the aunt's primary epithelial ovarian cancer, with the reported ages correct. No familial pathogenic-variant result had yet been identified; the paternal history remained part of assessment.
- 3The supplied specialist assessment named CanRisk/BOADICEA as its modelling framework and reported a 32% lifetime breast-cancer risk from age 20. This is an illustrative reported output with a specified horizon; no real patient calculation is represented.
- 4The specialist classified the supplied lifetime estimate as high risk under NICE's threshold of 30% or greater, arranged genetics review of the informative affected relative and agreed a documented specialist surveillance and prevention discussion. A cancer-risk estimate was not substituted for carrier probability.
- 5At follow-up, the clinic confirmed receipt of the verified pedigree, recorded the high-risk category and sent the agreed surveillance/referral plan to the patient. She could explain that the estimate concerned future risk, while any new breast symptom still required assessment.
02New symptom pathwaySeparate risk assessment from diagnosisA person already classified as high risk develops a new firm breast lump between planned surveillance examinations.+
- 1Assess the current symptom through urgent clinical and diagnostic breast pathways instead of waiting for the next surveillance scan.
- 2Use age-appropriate imaging and representative tissue where indicated; a risk-model percentage neither proves nor excludes malignancy.
- 3Inform the genetics or high-risk team of the new diagnosis if confirmed, because it may change testing and family counselling.
- 4Recalculate future contralateral or second-primary risk only after the immediate diagnostic problem has been resolved.
03Uncertain pedigree pathwayAvoid false precisionA patient has been adopted and has no reliable biological family history but asks for an exact lifetime percentage.+
- 1Explain which major inputs are unavailable and collect robust personal factors, ancestry and prior breast pathology.
- 2Choose a model that can represent missing data and report a range or qualified estimate rather than inventing unaffected relatives.
- 3Base current screening on national and specialist eligibility criteria using the information that is known.
- 4Offer reassessment if biological history, genetic information or new breast pathology becomes available.
05Checking understandingVerify the reasoning, revisit uncertainties and apply feedback.
- Update the pedigree when a relative develops a new primary cancer, pathology is verified, or a constitutional result becomes available.
- Recalculate risk when age, breast biopsy history, menopausal treatment or genetic data change enough to alter surveillance or prevention eligibility.
- For a person in enhanced surveillance, track attendance, modality, result and the planned next test while retaining rapid review for interval symptoms.
- After lifestyle counselling, revisit achievable alcohol, weight, activity and smoking goals without suggesting that behaviour can reduce inherited risk to zero.
06Special situationsVariants, exceptions and circumstances that change the usual approach.
Paternal history counts equally
A pathogenic autosomal dominant variant can pass from father to daughter or son even when few women on that side developed breast cancer.
Model outputs are conditional
A percentage is valid only for the inputs, assumptions, population calibration and time horizon used at that assessment.
Risk is not carrier probability
A person may have high lifetime breast-cancer risk without a high BRCA probability, and a variant carrier can have age-specific risk that changes over time.
Absolute numbers aid decisions
“Eight in 100 over ten years” is usually easier to weigh against medicine or surgery harms than a relative-risk multiplier alone.
07Common pitfallsFrequent interpretation and management errors.
- 01
Ignoring paternal relatives can miss an autosomal dominant cancer-predisposition pattern that is transmitted through apparently unaffected men.
- 02
Entering unverified ovarian or breast cancer labels as certain can markedly inflate a model and distort genetics eligibility.
- 03
Quoting a lifetime percentage without the person’s current age or time horizon makes the number hard to interpret and easy to misuse.
- 04
Allowing scheduled high-risk surveillance to delay work-up of a new symptom confuses prevention with current cancer diagnosis.