Invasive carcinoma of the breast can be classified into:
- Invasive ductal carcinoma (75-85%)
- Invasive lobular carcinoma (10%)
- Other subtypes (5%), such as medullary carcinoma or colloid carcinoma
Historically, ductal and lobular carcinomas were originally divided on the basis that ductal carcinomas arise in the ducts and lobular carcinomas arise in the lobules; it is now known that almost all breast carcinomas arise in the terminal duct lobular unit but this classification remains in use due to the different behaviour of the two subtypes.
Carcinoma of the breast is the most common cancer in the Western world and accounts for 20% of all cancers in women in the UK, with 1 in 10 women developing breast cancer in their lifetime (the prevalence of the condition in males is significantly less).
Classification of Breast cancer
Invasive Ductal Carcinoma
Invasive ductal carcinoma (IDC) is the most common type of breast carcinoma, constituting 80% of all cases.
IDCs can be further classified into tubular, cribriform, papillary, mucinous (/colloid), or medullary carcinomas, all showing distinct patterns of growth*.
*Tubular, cribriform and papillary subtypes are well-circumscribed and show the most favourable prognoses
Invasive Lobular Carcinoma
Invasive lobular carcinoma (ILC) is the second most common type of breast cancer, constituting 10% of all invasive breast cancers. ILC is more common in older women.
It is characterised by a diffuse (stromal) pattern of spread that makes detection more difficult. By the time of diagnosis, tumours are often quite large.
Female sex and age are the most significant risk factors for breast cancer, with the risk of breast cancer doubling every ten years until menopause.
Mutations to certain genes are well-documented risk factors, most importantly the tumour suppressor genes BRCA1 and BRCA2.
Family history in a first-degree relative*, previous benign disease, obesity, alcohol consumption, and geographic variation (more common in developed countries) are all significant risk factors for breast malignancy.
The degree of exposure to unopposed oestrogen has also been well-documented to cause an increase in the risk of developing breast cancer. Factors that influence this include early menarche, late menopause, nulliparous women, first pregnancy after 30 years of age, and oral contraceptives or HRT use.
Differential Diagnosis
All suspected breast cancers should be referred for a triple assessment, where a definitive diagnosis can be obtained.
Benign tumours, breast cysts, or infective causes are all potential differentials, the majority of which are identified following suitable imaging and histology.
Investigation and Management
The current gold standard for diagnosis of breast lumps is via the triple assessment, involving examination, imaging, and histology or cytology. Management for breast malignancies is extensive and variable and is explained further.
Prognosis
Overall, nodal status is the single most important prognostic factor in breast cancer, however, size, grade, and receptor status also influence prognosis.
The Nottingham Prognostic Index (NPI)* is a widely used clinicopathological staging system for primary breast cancer prognosis. It is calculated by:
(Size x 0.2) + Nodal Status + Grade
Size is the diameter of the lesion in cm, nodal status is the number of axillary lymph nodes involved (0 nodes=1, 1-4 nodes=2, >4 nodes=3), and grade is based on Bloom-Richardson classification
| Score | 5 Year Survival |
| ≥2.0 and ≤2.4 | 93% |
| >2.4 and ≤3.4 | 85% |
| >3.4 and ≤5.4 | 70% |
| >5.4 | 50% |
*Importantly, this data was first published in 1992 and a variety of other factors, outside of the NPI, such as vascular invasion and receptor status, are now also used in prognostics.
Due to potential new targeted therapies, receptor status is now a key feature in determining mortality rates. All breast malignancies should be checked for their estrogen receptor (ER), Progesterone Receptor (PR), and Human Epidermal growth factor Receptor (HER2) status, allowing for suitable treatment options to be developed.
Breast Screening Programmes
In the UK, the NHS breast cancer screening programme currently invites women aged 50-70 years to have a mammogram every three years; any abnormalities identified will be referred to the breast clinic for triple assessment.
Paget’s Disease of the Nipple
Paget’s disease of the nipple is a rare condition that presents as a roughening, reddening, and slight ulceration of the nipple. The vast majority of Paget’s (97%) will also have an underlying neoplasm, either in situ or invasive disease, and it is associated with 1-4% of all cases of breast cancer.
Microscopically there is involvement of the epidermis by malignant ductal carcinoma cells. The mechanism behind Paget’s disease is currently unknown, however, it is hypothesised that either malignant cells migrate from the ducts to the nipple surface or the cells of the nipple themselves become malignant.
Investigations
A biopsy is needed to confirm diagnosis; in certain cases, the entire nipple may be removed for histological examination.
Given its association with malignancy, complete breast and axilla examinations should also be performed. Mammograms, ultrasounds, or MRI breast may also be warranted.
Management
First line management of Paget’s disease is surgical. The type of surgery depends on how advanced the underlying breast cancer is, but in all cases, the nipple and areola will need to be removed.
