Case 31 A breast lump that disappears
Charlotte was a 39-year-old woman with no significant past medical history. She consulted Dr Duffield because she had felt a lump in her left breast the day before. Dr Duffield examined both breasts but could find no abnormality or asymmetry.
What would you do now?
Dr Duffield advised Charlotte that she could find no abnormality but to return if she felt that her left breast had changed or that she could feel a lump.
Two years later Charlotte consulted another general practitioner at the practice with a breast lump. There was a palpable lump and the doctor referred her urgently under the UK NHS ‘Two Week Rule’ guidance. Charlotte was diagnosed with a left breast cancer and underwent a local excision. The histological diameter of the tumour was 17 mm.
Do you think her claim will succeed?
Expert comment
Delayed or missed diagnoses of breast cancer remain very common causes of claims against general practitioners and, increasingly, nurse practitioners. The standard required of the general practitioner is very straightforward and the cases normally come down to the question of whether or not the breast examination was competently carried out. Surprisingly, there are still general practitioners, usually of the older generation, who either examine the woman while seated or examine only one breast. The correct examination technique is set out in many textbooks and also in the excellent review article ‘Does this patient have breast cancer?’ (Barton et al., 1999).
The standard required of UK general practitioners is objectively fairly simple and is set out in the 2005 NICE guidance document: Referral Guidelines for Suspected Cancer in Adults and Children and in Guidelines for the Referral of Patients with Breast Problems (Austoker & Mansel, 2003).
In a woman aged 30 years and older with a discrete lump that persists after her next period, or presents after menopause, an urgent referral should be made. A woman with asymmetric (‘dominant’) breast nodularity who is aged under 35 without a family history of breast cancer should be re-examined after an interval and, if the asymmetry has disappeared, she should be reassured.
In practice these cases tend to come down to the question of whether or not the lump should have been detected to competent examination. They are cases in which the question of the cell kinetics of tumours, normally only relevant to specialists commenting on the consequences of any breach of duty (medical causation), become relevant to the question of breach of duty.
What size was the lump likely to be two years earlier? The second question is what size of lump is detectable to competent examination by an average general practitioner?
The standard simplified model of tumour growth is that of exponential (Gompertzian) growth. The first cancerous cell divides and the cells continue to double in number and size once every set period of time. This time is the tumour volume doubling time. Aggressive tumours may double every 10–20 days while more indolent tumours may have doubling times of a year or more. Some awareness of cancer kinetics and the performance characteristics of clinical breast examination (CBE) may inform decisions about how to approach the problem of a patient’s subjectively noticed breast asymmetry.
The human body is made up of about 1013 cells or about 241 cells. A lethal cancer load is unlikely to contain more than 240 cells. It takes 40 doubling times to reach this extent. A 5 mm diameter cancer has about 227 cells and a 1 cm tumour about 230 cells (it takes 3 volume doubling times for the tumour to double in linear diameter).
Breast cancers in women under the age of 50 have doubling times of about 44–147 days with a mean of 80 days. For patients over 50 the mean is 157 days with a range of 121–204 days (Peer et al., 1993). Thus, by the time the tumour is 1 cm in size it has divided about 30 times and death would probably be in another 10 doubling times. A tumour that is 1 cm in diameter will be 2 cm in diameter 3 volume doubling times later. This increase in size may take anything from four months to two years.
How sensitive is clinical breast examination (CBE)?
There are a number of factors that are likely to determine whether a breast lump is clinically palpable. The most important factor is likely to be the size of the lump. Other factors are likely to be:
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