Normal histology	Histopathology	Pathological basis of disease	Clinical findings	
•	Each breast consists of 15-25 independent glandular units called breast lobes, each consisting of a compound tubulo-acinar gland.
•	The lobes are embedded in a mass of adipose tissue which is subdivided by collagenous septa.
•	Each breast lobe is divided into a variable number of breast lobules, each lobule consisting of a system of ducts, the alveolar ducts, from which large numbers of secretory alveoli develop during pregnancy.
•	The duct system is lined by cuboidal or low columnar epithelial cells with oval nuclei & prominent nucleoli.
•	A discontinuous layer of plump myoepithelial cells with unstained cytoplasm surrounds the ductal lining cells.	Abnormal histology:
•	Extensive proliferation of ductal epithelial cells.
•	Composed of malignant cells disposed in cords, often single-file, solid cell nests, tubules & anastomosing sheets with bands of collagen between them.
•	‘Scirrhous’ appearance is due to this marked increase in dense fibrous tissue stroma.
•	Pattern of growth: ductual carcinoma appears to radiate from a central area of desmoplasia.
•	Tumor cells have invaded through the basement membrane, infiltrating into the surrounding fibrous stromal tissue.
•	Tumor cells exhibit cohesion, forming either columns, linear chains or cluster of cells.

Cellular characteristics:
•	Hyperchromatic nuclei
•	Increased nuclear-cytoplasmic ratio
•	Nuclear pleomorphism	Found more commonly in:
•	Women with a strong family history of breast cancer.
•	Older women.
•	Women who have an early menarche & late menopause.
•	Nulliparous women as compared to multiparous women.
•	Women having their first child after age of 30.

Etiology:
•	Genetic factors: BRCA1 & BRCA 2 mutations.
•	Hormone imbalances: increased exposure to endogenous estrogens.
•	Environmental influences: dietary fat

Cellular changes:
•	Increased expression of oncogenes.
•	Decreased expression or function of tumor-suppressor genes.
•	Loss of cell adhesion
•	Alterations in cell structure
•	Increased expression of cell cycle proteins.
•	Increased expression of angiogenic factors.
•	Increased expression of proteases. 	Physical symptoms:
•	Tumor fixation
•	Retraction of nipple
•	Dimpling of skin
•	Lymphedema
•	Enlarged erythematous & swollen breast.
•	Nipple discharge & bleeding.

Mammographic appearance:
•	Spiculated density with irregular borders.
•	Architectural distortion
•	Calcifications: calcium deposits form on either secretory material or necrotic debris.

Lymph node metastasis:
•	Axillary
•	Supraclavicular
•	Internal mammary

Prognostic factors:
•	Lymph node metastases
•	Invasiveness
•	Tumor size
•	Histologic subtypes
•	Tumor grade
•	Estrogen / progesterone receptor status

Therapy:
•	Local control: surgery & postoperative radiation.
•	Systemic control: hormonal treatment, chemotherapy, or both.