Oncology · Breast Cancer
The facts most likely to be tested
Invasive ductal carcinoma is the most common histologic subtype of breast cancer, typically presenting as a firm, fixed, irregular mass.
Invasive lobular carcinoma is frequently bilateral and multifocal, often presenting as a subtle thickening rather than a discrete mass.
Paget disease of the breast presents as an eczematous, pruritic, scaly rash on the nipple and is highly associated with underlying ductal carcinoma in situ (DCIS).
Inflammatory breast cancer is a clinical diagnosis characterized by erythema, edema, and peau d'orange appearance caused by dermal lymphatic invasion.
BRCA1 and BRCA2 gene mutations significantly increase the lifetime risk of breast and ovarian cancer, warranting prophylactic bilateral salpingo-oophorectomy.
Sentinel lymph node biopsy is the standard of care for staging the axilla in clinically node-negative patients to avoid the morbidity of axillary lymph node dissection.
Trastuzumab is the targeted therapy indicated for patients with HER2/neu overexpression, which is associated with a more aggressive clinical course.
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A 54-year-old female presents with a 3-month history of a persistent, itchy, scaly rash on her left nipple that has failed to respond to topical corticosteroids. Physical examination reveals erythematous, crusting, and ulcerated skin involving the nipple-areola complex. There is no palpable breast mass, but a small, fixed lymph node is noted in the left axilla. A punch biopsy of the skin is performed.
What is the most likely diagnosis?
Paget disease of the breast
The patient's presentation of a persistent, eczematous nipple lesion is classic for Paget disease, which is pathognomonic for underlying ductal carcinoma in situ (DCIS) or invasive breast cancer.
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Etiology / Epidemiology
Most common cancer in women; BRCA1/2 mutations and prolonged estrogen exposure (early menarche, late menopause) are primary drivers.
Clinical Manifestations
Painless, hard, fixed mass; peau d'orange skin changes and Paget disease of the breast (nipple scaling) are pathognomonic.
Diagnosis
Mammography is the gold standard for screening; core needle biopsy is required for definitive tissue diagnosis.
Treatment
Lumpectomy plus radiation or mastectomy; Tamoxifen is the first-line endocrine therapy for premenopausal patients.
Prognosis
Survival is highly dependent on TNM staging; metastasis to bone, liver, lung, and brain are the primary causes of mortality.
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Epidemiology & Etiology
Incidence increases with age, with the majority of cases occurring in women >50. Major risk factors include nulliparity, late first pregnancy, and first-degree relative history. Genetic predisposition via BRCA1/2 accounts for 5-10% of cases, significantly increasing lifetime risk.
Pertinent Anatomy
Most cancers originate in the terminal duct lobular unit. The axillary lymph nodes are the primary drainage site and the most common location for early regional spread.
Pathophysiology
Uncontrolled proliferation of epithelial cells leads to tumor formation. Overexpression of HER2/neu or hormone receptor status (ER/PR) dictates tumor aggressiveness and therapeutic targets. Local invasion causes the classic peau d'orange appearance due to lymphatic obstruction.
Clinical Manifestations
Patients typically present with a painless, hard, irregular mass. Red flags include nipple retraction, bloody nipple discharge, or skin dimpling. Paget disease of the breast presents as an eczematous, itchy, scaling lesion on the nipple, often signaling underlying ductal carcinoma in situ.
Diagnosis
Screening begins with mammography (typically age 40-50). Suspicious findings (BI-RADS 4/5) mandate a core needle biopsy for histology. Sentinel lymph node biopsy is performed during surgery to assess nodal involvement.
Treatment
Surgical options include breast-conserving therapy (lumpectomy + radiation) or mastectomy. Adjuvant therapy depends on receptor status: Tamoxifen (premenopausal) or Aromatase inhibitors (postmenopausal). Tamoxifen carries an increased risk of endometrial cancer and thromboembolism.
Prognosis
Prognosis is determined by TNM staging and receptor status. HER2-positive tumors are more aggressive but respond to Trastuzumab. Regular follow-up is required to monitor for local recurrence or distant metastasis.
Differential Diagnosis
Fibroadenoma: mobile, rubbery, painless mass
Fibrocystic changes: bilateral, cyclic, tender masses
Breast abscess: localized erythema, warmth, and fever
Intraductal papilloma: unilateral, bloody nipple discharge
Fat necrosis: history of trauma, firm/ill-defined mass