Malignant Processes of the Breast

Comprehensive vocabulary flashcards covering the pathophysiology, histologic subtypes, sonographic and mammographic criteria, risk factors, and metastatic pathways of malignant breast diseases.

Dense Breast Equation

The clinical progression linking prolonged lifetime estrogen and progesterone exposure to increased risk: Early menarche + Late first pregnancy + Few or no pregnancies + Little or no breastfeeding + Late post-menopause = High Menstrual Life score = Dense breasts = Increased risk of breast cancer.

Breast Cycle Hormonal Regulation

The cyclic physiological process where estrogen causes ducts to grow and progesterone causes lobules to grow and develop during menstrual cycles, while prolactin induces milk production and oxytocin triggers milk release during pregnancy and breastfeeding.

Terminal Ductal Lobular Unit (TDLU) Anatomy

The essential functional glandular structure of the breast where most malignancies arise, composed of an extralobular terminal duct and a lobule containing intralobular ductules.

Desmoplastic Response

A host stromal tissue reaction that attempts to halt tumor invasion by generating dense fibrosis; this fibrotic reaction causes acoustic shadowing and is typically observed in slower-growing tumors that have sufficient time to develop.

Spiculation

Radiographic or sonographic finger-like extensions extending from a malignant mass into adjacent breast parenchyma, thought to result from a desmoplastic response to tumor invasion.

Taller-Than-Wide Orientation

A suspicious sonographic finding where a breast mass has a greater anterior-posterior dimension than transverse dimension, reflecting aggressive tumor growth that crosses normal connective tissue planes.

Ductal Carcinoma In Situ (DCIS)

The most common non-invasive breast carcinoma (also termed intraductal carcinoma), defined by the proliferation of abnormal epithelial cells within extralobular ducts that have not breached the basement membrane into the surrounding stroma.

Comedo DCIS

A high-grade histologic subtype of DCIS characterized by central cellular necrosis resulting from cell death (which often calcifies within the duct) and carrying a high incidence of progressing to high-grade invasive carcinoma.

Cribriform / Micropapillary DCIS

A noncomedo, less aggressive subtype of DCIS with a better prognosis, characterized histologically by small papillary projections forming gaps between cells that produce a 'swiss-cheese pattern' microscopically.

Nuclear Grade

A cytological grading assessment comparing the features of malignant cell nuclei to normal mammary cellular nuclei (categorized as low, intermediate, or high) used to help forecast tumor behavior.

Lobular Carcinoma In Situ (LCIS)

A non-invasive atypical neoplasia originating in the intralobar ductules; it occurs more frequently in premenopausal women, is characteristically bilateral and multicentric, and rarely forms a distinct mammographic or sonographic mass.

Invasive Ductal Carcinoma (IDC)

The most common invasive breast cancer ($75\%$ to $80\text{--}90\%$ of cases), occurring when malignant ductal epithelial cells breach the basement membrane into the stromal tissue, presenting as a solitary, hard, fixed mass with scirrhous features.

Invasive Lobular Carcinoma (ILC)

The second most common invasive breast cancer ($8\text{--}15\%$ of cases), originating in lobules; it is highly infiltrative, frequently bilateral, multifocal, and multicentric, and often appears on imaging solely as architectural distortion, parenchymal thickening, or asymmetry without a discrete mass.

Multifocal Breast Cancer

The presence of two or more distinct tumor foci located within the same breast quadrant or separated by a distance of less than $5\,\text{cm}$, originating from spread within the same ductal system.

Multicentric Breast Cancer

The presence of multiple malignant tumor foci arising in different breast quadrants or separated by a distance equal to or greater than $5\,\text{cm}$.

Medullary Carcinoma

A histologic subtype of invasive ductal carcinoma (accounting for up to $5\%$ of invasive cancers and $11\%$ in women under $35$) characterized by a fast-growing, circumscribed, densely cellular mass with central necrosis/hemorrhage and low incidence of nodal involvement.

Colloid (Mucinous) Carcinoma

An uncommon, slow-growing breast carcinoma ($\approx 3\%$ of malignancies) containing syrupy or gelatinous mucin, typically presenting in older women ($75$ or older) as a circumscribed, complex mass with a favorable prognosis.

Papillary Carcinoma

A rare subtype of invasive duct carcinoma ($<3\%$) primarily affecting postmenopausal women, typically situated in large central ducts, presenting clinically with bloody or serous nipple discharge and sonographically as an intraductal nodule or vascular solid tumor within a cystic lesion.

Tubular Carcinoma

A well-differentiated subtype of invasive ductal cancer ($2\text{--}3\%$ of invasive tumors) arising in peripheral TDLUs, presenting on sonography as a small, markedly hypoechoic, spiculated mass with acoustic shadowing, associated with a low rate of metastasis.

Phyllodes Tumor

A fibroepithelial neoplasm (also called cystosarcoma phyllodes or giant fibroadenoma) containing narrow, cyst-like clefts of mucinous or hemorrhagic fluid, presenting in patients aged $30\text{--}50$; up to $25\%$ contain malignant degeneration, and $10\%$ can metastasize hematogenously to lungs, pleura, and bone.

Paget Disease of the Nipple

A form of breast malignancy ($1\text{--}5\%$ of breast cancers) characterized by infiltration of the nipple epidermis by malignant cells, producing eczematous skin changes (reddening, scaling, crusting) and often accompanied by an underlying ductal carcinoma.

Inflammatory Carcinoma

A rare, aggressive, high-grade infiltrating ductal carcinoma that rapidly invades dermal lymphatics, resulting in warm, swollen, hard breasts, diffuse erythema, thickened Cooper's ligaments, and a peau d'orange appearance.

Peau d'orange

An 'orange-peel' skin texture caused by tumor obstruction of cutaneous lymphatic drainage, resulting in skin edema, dimpling, and anterior-posterior skin thickening exceeding $2\,\text{mm}$.

Primary Breast Lymphoma

A rare breast malignancy ($<1\%$ of malignancies) that presents as a rapidly growing, markedly hypoechoic, hypervascular mass with distal sound enhancement and an absence of microcalcifications.

Axillary Lymph Node Level I

Axillary lymph nodes situated anatomically lateral and inferior to the pectoralis minor muscle.

Axillary Lymph Node Level II

Axillary lymph nodes located anatomically underneath the pectoralis minor muscle.

Rotter Nodes

Interpectoral axillary lymph nodes located specifically between the pectoralis major and pectoralis minor muscles, surgically considered part of Level II nodes.

Axillary Lymph Node Level III

Infraclavicular axillary lymph nodes situated anatomically medial and superior to the pectoralis minor muscle.

Axillary Lymph Node Levels (I, II, III)

The surgical and anatomic staging division of axillary lymph drainage categorized relative to the pectoralis minor muscle: Level I (lateral and inferior), Level II (underneath), and Level III (infraclavicular: medial and superior).

Sentinel Lymph Node

The initial lymph node or small cluster of nodes that first receives lymphatic drainage from a primary breast carcinoma, representing the earliest site reached by metastasizing cancer cells.

Intercostal-to-Vertebral Venous Pathway

The vascular route responsible for breast cancer hematogenous metastasis to bone, occurring via communications between the intercostal veins and the vertebral venous plexus.

Superficial Venous Cross-Contralateral Route

The vascular communications across the anterior chest wall between the superficial veins of the right and left breasts that facilitate metastasis to the opposite breast.

Nonmammary Metastases to the Breast

Secondary breast tumors (comprising approximately $2\%$ of breast malignancies) originating from distant primary sites, most commonly melanoma, followed by lung carcinoma, ovary, sarcoma, and GI tract tumors.