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Pathology — High-Yield — USMLE Step 2 CK Notes
Free, high-yield revision notes for USMLE Step 2 CK. Read here, or drill the same material as questions and flashcards in the app.
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Cellular adaptation, in order of escalation
- Hypertrophy — bigger cells (e.g. cardiac in hypertension)
- Hyperplasia — more cells (e.g. endometrium under unopposed oestrogen)
- Metaplasia — one differentiated type replaced by another; reversible (Barrett)
- Dysplasia — disordered growth, premalignant
- Anaplasia — loss of differentiation, hallmark of malignancy
Cell injury and death
- Reversible: cellular swelling, ribosomal detachment, mitochondrial swelling
- Irreversible: membrane damage, calcium influx, mitochondrial vacuolisation
- Necrosis (coagulative, liquefactive, caseous, fat, fibrinoid, gangrenous) vs apoptosis (programmed, no inflammation)
- Red (haemorrhagic) infarcts in loose, dual-supply tissue (lung, bowel); pale infarcts in solid single-supply organs (heart, kidney, spleen)
Inflammation
- Acute: neutrophils, minutes to days, mediated by histamine, prostaglandins, leukotrienes
- Chronic: lymphocytes, macrophages, granulomas (epithelioid histiocytes)
- Granuloma differential: TB, fungi, sarcoid, Crohn, cat-scratch, foreign body
Neoplasia — the associations that recur
- Squamous cell lung cancer → PTHrP → hypercalcaemia; small cell → ACTH and ADH
- Tumour suppressors need two hits (Rb, p53); oncogenes need one
- Psammoma bodies: papillary thyroid, serous ovarian, meningioma, mesothelioma
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