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Pathology - Invasive breast carcinomas
Definition: A collection of malignant epithelial tumors that infiltrate the breast and possess the ability to metastasize to distant locations. Epidemiology: The predominant cancer among women, with a lifetime risk of 1 in 8. • Incidence rates escalate significantly with advancing age, resulting in the majority of cases occurring in elderly women.
Aetiology: Early menarche, late menopause, elevated weight, excessive alcohol intake, oral contraceptive usage, and a favorable familial history are all correlated with an increased risk. Approximately 5% exhibit unequivocal indications of heredity. BRCA mutations confer a lifetime risk of invasive breast cancer of up to 85%.
Carcinogenesis • Recent genetic research has proposed that the evolution of breast cancer can be generally categorized into two types. The low-grade group, including low-grade invasive ductal carcinoma, classical lobular carcinoma, mucinous carcinoma, and tubular cancer, expresses hormone receptors, does not overexpress HER2, and lacks basal indicators. Genetically, they possess uncomplicated diploid or nearly diploid karyotypes and are characterized by the deletion of 16q and the amplification of 1q. The high-grade category (e.g., high-grade invasive ductal carcinoma, basal-like cancer) often lacks hormone receptors, overexpresses HER2, and exhibits basal signs. They possess intricate karyotypes characterized by several imbalanced chromosomal abnormalities. Common alterations encompass the deletion of 1p, 8p, and 17p, alongside the amplification of 1q and 8q.
Presentation • The majority of cases manifest symptomatically as a breast lump. • A growing percentage of asymptomatic cases are identified through screening mammography. Macroscopy Most breast carcinomas generate a solid stellate tumor within the breast. Cytopathology Fine needle aspiration (FNA) samples from breast carcinomas are generally characterized by high cellularity, comprising a poorly coherent assemblage of malignant epithelial cells.
Background: Bare bipolar nuclei are nonexistent. Histopathology Invasive ductal carcinomas, comprising 80%, are infiltrating carcinomas that lack distinctive features necessary for classification as specific histological types, such as lobular or tubular carcinoma; thus, they are often designated as 'no special kind.' Consequently, they constitute a heterogeneous array of tumors rather than a singular variety. In the future, this group is expected to be subdivided into more significant entities based on their genetic profiles.
Invasive lobular carcinomas (15%) consist of tiny, poorly cohesive cells with little cytoplasm, which typically proliferate in linear cords and wrap existing normal ducts.
Tubular carcinomas (5%) consist of well-organized tubular formations bordered by a single layer of epithelial cells exhibiting low-grade atypia.
Mucinous carcinomas (5%) are distinguished by the extensive synthesis of mucin in which the tumor cells are suspended. Basal-like carcinomas constitute a recently identified category of tumors revealed through the genetic profiling of several breast carcinomas. They frequently manifest in young women and are associated with BRCA mutations.
Morphologically, they generally exhibit sheets of markedly abnormal epithelial cells accompanied by a significant lymphocytic inflammatory infiltrate and central necrosis. Immunohistochemically, they are distinguished by the expression of basal-type keratins, such as cytokeratins 5 and 14. Basal-like tumors are often negative for estrogen receptors (ER) and progesterone receptors (PR), and are not amplified for Her2, hence classified as 'triple negative' tumors. These tumors exhibit a tendency for visceral metastasis, particularly to the lungs and brain.
Grading • All invasive breast tumors are histologically graded by evaluating nuclear pleomorphism, tubule development, and mitotic activity. Each attribute is evaluated on a scale from 1 to 3, and the cumulative scores yield a total ranging from 3 to 9. • 3–5 points represent grade 1 (well-differentiated). • 6–7 points = grade 2 (moderately differentiated). • 8–9 points = grade 3 (insufficiently differentiated). The primary prognostic determinant is the condition of the axillary lymph nodes. Additional significant criteria encompass tumor size, histology type, and histological grade.
Simplifi ed TNM 7 pathological staging of breast
carcinomas
Primary tumour (T)
pT1: tumour 2cm or less in size.
pT2: tumour > 2cm, but not > 5cm in size.
pT3: tumour > 5cm in size.
pT4: tumour of any size with extension to the chest wall and/or skin.
Regional lymph nodes (N)
pN0: no regional lymph node metastasis.
pN1: metastasis in 1–3 ipsilateral axillary lymph nodes.
pN2: metastasis in 4–9 ipsilateral axillary lymph nodes.
pN3: metastasis in 10 or more ipsilateral axillary lymph nod
Definition: A collection of malignant epithelial tumors that infiltrate the breast and possess the ability to metastasize to distant locations. Epidemiology: The predominant cancer among women, with a lifetime risk of 1 in 8. • Incidence rates escalate significantly with advancing age, resulting in the majority of cases occurring in elderly women.
Aetiology: Early menarche, late menopause, elevated weight, excessive alcohol intake, oral contraceptive usage, and a favorable familial history are all correlated with an increased risk. Approximately 5% exhibit unequivocal indications of heredity. BRCA mutations confer a lifetime risk of invasive breast cancer of up to 85%.
Carcinogenesis • Recent genetic research has proposed that the evolution of breast cancer can be generally categorized into two types. The low-grade group, including low-grade invasive ductal carcinoma, classical lobular carcinoma, mucinous carcinoma, and tubular cancer, expresses hormone receptors, does not overexpress HER2, and lacks basal indicators. Genetically, they possess uncomplicated diploid or nearly diploid karyotypes and are characterized by the deletion of 16q and the amplification of 1q. The high-grade category (e.g., high-grade invasive ductal carcinoma, basal-like cancer) often lacks hormone receptors, overexpresses HER2, and exhibits basal signs. They possess intricate karyotypes characterized by several imbalanced chromosomal abnormalities. Common alterations encompass the deletion of 1p, 8p, and 17p, alongside the amplification of 1q and 8q.
Presentation • The majority of cases manifest symptomatically as a breast lump. • A growing percentage of asymptomatic cases are identified through screening mammography. Macroscopy Most breast carcinomas generate a solid stellate tumor within the breast. Cytopathology Fine needle aspiration (FNA) samples from breast carcinomas are generally characterized by high cellularity, comprising a poorly coherent assemblage of malignant epithelial cells.
Background: Bare bipolar nuclei are nonexistent. Histopathology Invasive ductal carcinomas, comprising 80%, are infiltrating carcinomas that lack distinctive features necessary for classification as specific histological types, such as lobular or tubular carcinoma; thus, they are often designated as 'no special kind.' Consequently, they constitute a heterogeneous array of tumors rather than a singular variety. In the future, this group is expected to be subdivided into more significant entities based on their genetic profiles.
Invasive lobular carcinomas (15%) consist of tiny, poorly cohesive cells with little cytoplasm, which typically proliferate in linear cords and wrap existing normal ducts.
Tubular carcinomas (5%) consist of well-organized tubular formations bordered by a single layer of epithelial cells exhibiting low-grade atypia.
Mucinous carcinomas (5%) are distinguished by the extensive synthesis of mucin in which the tumor cells are suspended. Basal-like carcinomas constitute a recently identified category of tumors revealed through the genetic profiling of several breast carcinomas. They frequently manifest in young women and are associated with BRCA mutations.
Morphologically, they generally exhibit sheets of markedly abnormal epithelial cells accompanied by a significant lymphocytic inflammatory infiltrate and central necrosis. Immunohistochemically, they are distinguished by the expression of basal-type keratins, such as cytokeratins 5 and 14. Basal-like tumors are often negative for estrogen receptors (ER) and progesterone receptors (PR), and are not amplified for Her2, hence classified as 'triple negative' tumors. These tumors exhibit a tendency for visceral metastasis, particularly to the lungs and brain.
Grading • All invasive breast tumors are histologically graded by evaluating nuclear pleomorphism, tubule development, and mitotic activity. Each attribute is evaluated on a scale from 1 to 3, and the cumulative scores yield a total ranging from 3 to 9. • 3–5 points represent grade 1 (well-differentiated). • 6–7 points = grade 2 (moderately differentiated). • 8–9 points = grade 3 (insufficiently differentiated). The primary prognostic determinant is the condition of the axillary lymph nodes. Additional significant criteria encompass tumor size, histology type, and histological grade.
Simplifi ed TNM 7 pathological staging of breast
carcinomas
Primary tumour (T)
pT1: tumour 2cm or less in size.
pT2: tumour > 2cm, but not > 5cm in size.
pT3: tumour > 5cm in size.
pT4: tumour of any size with extension to the chest wall and/or skin.
Regional lymph nodes (N)
pN0: no regional lymph node metastasis.
pN1: metastasis in 1–3 ipsilateral axillary lymph nodes.
pN2: metastasis in 4–9 ipsilateral axillary lymph nodes.
pN3: metastasis in 10 or more ipsilateral axillary lymph nod
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