Breast Cancer

❓What❓

“Breast cancer” describes a diverse group of carcinomas that arise from the epithelial elements of breast tissue, which can stratified into those that are “in situ” (i.e. still confined within the mammary ducts, but considered pre-cancerous) vs. “invasive” (i.e. spreading beyond the mammary ducts)

❓Epidemiology❓

Worldwide most frequently diagnosed type of malignancy, & most common malignancy of females in the U.S.

Histologically, ~70-80% of invasive lesions are ductal, ~10% are lobular, ~10% are mixed, & 10% other (e.g. metaplastic, papillary)

~1% of all breast cancers occur in males, & in males risk factors include age, BRCA1/2 positivity (as well as CHEK2, PALB2), radiation exposure, high estradiol levels & gynecomastia, liver disease, & obesity

❓Presentation❓

Local

~85%: asymptomatic & diagnosed via screening mammography

~15%: breast mass, skin changes (e.g. erythema, thickening, dimpling “peau d’orange”), nipple changes (e.g. flattening, inversion, discharge, crusting), painful breast swelling/engorgement, axillary lymphadenopathy

Metastatic

Bone (~50-70%): bone pain & isolated ALP ↑, osteolytic > osteoblastic radiographic appearance (~15-20% are predominantly -blastic), pathologic fractures, spinal cord compression

Liver (~40-50%): ↑↑↑ ALP > ↑ TBili (infiltrative pattern), low-grade transaminosis, “cirrhotic-appearing liver” (i.e. “pseudocirrhosis”) → portal HTN (< 30%, ↑ risk if chemotherapy culprit of portosinusoidal vascular disease)

Lung (~15-25%): parenchymal metastasis → large airway obstructions, pleural effusions

Brain (~10-30%): provoked seizures, focal neurologic deficits

❓Diagnosis❓

Local

Mammography vs. US vs. both → perQ needle biopsy

⚪ If signs of inflammatory breast cancer (i.e. rapidly progressive tender mass, skin changes), full-thickness skin biopsy should also be pursued to evaluate for dermal lymphatic invasion

⚪ Divergent types of cancers within the breast beyond those routinely considered in the “breast cancer” group include breast sarcoma (consider if prior radiation or lymphedema), breast implant-associated anaplastic large cell lymphoma (consider if textured implants), & Phyllodes tumor (originate from fibroepithelial cells)

⚠️ Note: the diagnostic pathway above is pursued when there is crystallized suspicion for breast cancer. If suspicion for breast cancer is absent, it can be missed on chest CT if you’re not looking for it. (The sensitivity of chest CT by trained radiologists specifically looking for it is ~85%, with slightly lower sensitivity if no IV contrast is given, compared to ~79% sensitivity of mammography, & compared to only ~54% when radiologist isn’t explicitly looking for it.)

Metastatic