Structural and functional framework
To understand the localization of pathological processes, it is important to know the basic anatomy. The mammary gland consists of 15–20 lobes separated by adipose tissue and fibrous septa.
The main structural and functional unit is the terminal ductulo-lobular unit. It is located within the loose interlobular stroma and consists of a terminal duct with branching alveoli and acini.
Normally, the ducts and alveoli are lined by two layers of cells:
- Cuboidal epithelium (inner layer).
- Myoepithelial cells (outer layer).
Hyperplastic and neoplastic processes most frequently originate from the epithelial elements of the terminal unit.
Diseases that increase cancer risk
The development of invasive cancer is often preceded by background and precancerous changes in the breast tissue.
Fibrocystic diseases This is the most common pathology, diagnosed in more than 10% of women aged 35–40. Macroscopically, it manifests as painful nodes. If the process is accompanied by atypical epithelial hyperplasia (formation of multilayered solid, cribriform, or papillary structures), it is officially considered a precancerous condition.
Radial scar A stellate scar-like lesion with a center composed of hyalinized collagen and obliterated ducts, and a periphery showing hyperplastic tubular structures. It may mimic cancer macroscopically and can be a true source of malignant transformation (the risk depends on the severity of dysplasia).
Intraductal papilloma Papillary proliferations within the ducts, presenting with bloody nipple discharge. Solitary papillomas have a favorable prognosis, but multiple lesions (frequently occurring in young women) increase the risk of cancer development by 4–6 times.
Epidemiology and risk factors of breast cancer
Breast cancer (Carcinoma mammae) predominates in countries with a high standard of living, where its incidence exceeds 26% of all female malignancies. Tumor development is multifactorial, but it is always driven by hyperestrogenemia.
Risk-increasing factors:
- Prolonged reproductive period (early menarche and late menopause).
- Nulliparity or first full-term pregnancy at age 30 or older.
- Use of estrogen medications.
- Presence of hormonally active tumors (e.g., granulosa cell tumor or ovarian thecoma synthesizing estrogens).
Protective factors:
- Early pregnancy and childbirth.
- Prolonged and full breastfeeding.
The concept of the "Western lifestyle"
According to the WHO concept, a specific lifestyle directly affects the likelihood of developing breast cancer. This refers to a combination of a high-calorie diet (high in fats and proteins) and low physical activity, which inevitably leads to obesity and insulin resistance.
How this leads to cancer (pathogenesis):
- Hyperinsulinemia develops and insulin-like growth factor levels rise.
- Peripheral estrogen synthesis is enhanced in adipose tissue.
- Sex hormone-binding globulin concentrations decrease.
- Conclusion: the level of free (bioavailable) estrogen in blood plasma sharply increases, which begins to continuously stimulate the proliferation of the glandular epithelium.
Briefly: answers to topical questions
What risk factors contribute to the development of breast cancer?
Breast cancer development is promoted by genetic, exogenous, hormonal, and histological risk factors.
- Genetic factors — a burdened family history of cancer and mutations in BRCA1, BRCA2, PALB2, TP53, CDH1, PTEN genes.
- Hormonal factors — hyperestrogenemia, prolonged reproductive period, nulliparity or first pregnancy after 30 years of age, hormonally active ovarian tumors, hormone replacement therapy.
- Exogenous factors — radiation exposure, alcohol consumption, use of oral contraceptives.
- Histological factors — a history of biopsy or surgery for atypical breast hyperplasia.
What are the histological forms of non-invasive (in situ) breast cancer?
Two main histological forms of non-invasive breast cancer are distinguished.
- Ductal carcinoma (carcinoma in situ) — characterized by the proliferation of atypical epithelium within the ducts without invasion into the surrounding stroma, capable of intracanalicular spread.
- Lobular carcinoma (carcinoma in situ) — non-invasive involvement of the breast lobules.
The classification also mentions other and unspecified forms of in situ carcinoma.
What are the main histological types of invasive breast cancer?
The main histological types of invasive breast cancer include ductal and lobular carcinomas, as well as a number of rarer forms.
- Invasive ductal carcinoma — the most common histotype, forming sheets, cords, and tubules within the fibrous stroma.
- Invasive lobular carcinoma — cells form strands or chains infiltrating the stroma.
- Medullary carcinoma — large pleomorphic cells with prominent lymphocytic infiltration of the stroma.
- Colloid carcinoma — characterized by the presence of mucin "pools" containing groups of tumor cells.
- Papillary carcinoma — a rare form of invasive cancer.
- Tubular carcinoma — a rare form of invasive cancer.
- Metaplastic carcinoma — a rare form of invasive cancer.
What are the molecular biological subtypes of breast cancer?
Sources indicate that the molecular biological classification of breast cancer is based on the expression of estrogen receptors, progesterone receptors, HER2 status, and the Ki67 proliferative activity index.
The cited materials mention the following phenotypes:
- Luminal A phenotype.
- Luminal B phenotype.
- HER2-positive phenotype.
- Triple-negative phenotype.
To which regional lymph nodes does lymphogenous metastasis of breast cancer occur?
Lymphogenous metastasis of breast cancer occurs predominantly via axillary lymph nodes.
Sources also indicate other groups of lymph nodes:
- Infraclavicular lymph nodes.
- Cervical lymph nodes.
- Subscapular lymph nodes.
- When the tumor is localized in the inner quadrants, lymph drains into the mediastinum and parasternal lymph nodes.
- The lymph node involvement classification also indicates subclavian and supraclavicular lymph nodes.
- Metastasis to the abdominal lymph nodes is possible from the lower sections.
What else to study on this topic
- Morphological differences between intracanalicular and pericanalicular fibroadenoma
- Features of malignant transformation of phyllodes tumor
- Sclerosing adenosis and breast fibrosis: differential diagnosis
- Mechanisms of breast cancer metastasis to the ovaries
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Other topics in "Chapter 20. Diseases of the Female Genital Organs and Mammary Glands"
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