Page 541 - Concise Pathology for Exam Preparation ( PDFDrive )

526 SECTION II Diseases of Organ Systems

Proliferating stroma

Compressed and
distorted ducts

FIGURE 19.3. Low-grade phyllodes tumour showing an exaggerated intracanalicular growth
pattern with increased stromal cellularity (H&E; 100X).

Q. Describe the aetiopathogenesis, clinical features and morphology
of carcinoma breast.
Ans. All breast carcinomas arise from the terminal duct lobular unit and usually affect
women in the third decade onwards.

Classification of Carcinoma Breast
1. Molecular classification: Almost all breast carcinomas are adenocarcinomas. They are
categorized into three biological groups from the therapeutic perspective:
(a) Oestrogen receptor (ER)-positive, human epidermal growth factor receptor
(HER)-2-negative (50–60% of all tumours) Also called ‘luminal A tumours’, they
are the most common type of breast cancer in patients with germline mutations in
BRCA2 (Flowchart 19.1)

Mutations in BRCA2 PIK3CA mutations
Normal breast Flat epithelial atypia Atypical ductal hyperplasia
1q gain
16q loss
ER-positive HER2-negative carcinoma Ductal carcinoma in situ or DCIS
FLOWCHART 19.1. Pathway of development of ER-positive, HER2-negative carcinoma breast.

Salient features:
• ER-positive, HER2-negative tumours are slow growing and respond well to
hormonal therapy.
• They are further subdivided into ‘low proliferation’ (more common) and ‘high
proliferation’ (less common) types.
• The ‘low proliferation’ type typically affects older women and men and is usu-
ally detected on routine mammographic screening. Histological types included
in this group are well or moderately differentiated lobular, tubular or mucinous
carcinomas.
• The ‘high proliferation’ group includes poorly differentiated lobular carcinomas
and are typically associated with BRCA mutations.

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