HY General Pathology Review for
USMLE Questions And Answers 2025
Anaplasia - answer:-Reversion to more immature cell type (i.e., a cell goes from, e.g.,
mature skin cell back to a stem cell). Means high-grade in cancer and poorer prognosis.
Aplasia - answer:-Tissue/organ doesn't develop. DiGeorge syndrome à aplasia of 3rd
and 4th pharyngeal pouches à missing thymus and parathyroid glands à T-cell
deficiency and hypocalcemia/hyperphosphatemia.
Atrophy - answer:-Diminished cell growth/size due to under-stimulation. Shows up on
NBME exam for effect on prostate tissue treated with orchiectomy in the setting of
prostatic adenocarcinoma; ¯ testosterone à ¯ DHT à ¯ prostate stimulation. Testicular
atrophy in the setting of exogenous anabolic steroid use; negative feedback at
hypothalamus/anterior pituitary à ¯ LH secretion à ¯ testicular stimulation. Thyroid
follicular atrophy with exogenous T3/T4 use; negative feedback at
hypothalamus/anterior pituitary à ¯ TSH secretion à ¯ thyroid stimulation. Menopausal
effects on ovaries and endometrium; don't confuse with menses, which are apoptotic.
Dysplasia - answer:-Cellular atypia that is precursor to cancer; cells are not yet
cancerous/tumorigenic. Reversible process; students often erroneously think it is
irreversible. USMLE is not going to ask, 'Is dysplasia irreversible or reversible?' What
they will do is give you, e.g., koilocytes with HPV 16/18 infection, and you need to know
most cases of low- and high-grade squamous epithelial dysplasia are reversible /
spontaneously regress.
Hyperplasia - answer:-Increased cell number. Endometrial hyperplasia due to
unopposed estrogen is highest yield example on USMLE. Anovulatory cycles à no
corpus luteum à no progesterone production à unopposed estrogen à endometrial
hyperplasia à increased risk of endometrial dysplasia and adenocarcinoma. I discuss
these mechanisms in high detail in my Obgyn / Repro PDF. Benign prostatic
hyperplasia (BPH) à older males will have large, hyperplastic prostates due to lifetime of
DHT exposure.
Hypertrophy - answer:-Increased cell size. Highest yield example on USMLE is
ventricular myocardial hypertrophy. High afterload causes concentric hypertrophy; high
preload causes eccentric hypertrophy. I discuss these mechanisms in the Cardio
section and HY Arrows PDF. Skeletal muscle hypertrophy in response to resistance
weight training.
Metaplasia - answer:-One mature cell type becomes another mature cell type;
reversible. Barrett esophagus caused by reflux is highest yield example on USMLE:
non-keratinized stratified squamous epithelium of distal esophagus à intestinal columnar
epithelium (meaning has goblet cells that produce mucous). The stomach doesn't have
goblet cells; it has mucous neck cells, aka foveolar cells.
,HY General Pathology Review for
USMLE Questions And Answers 2025
Neoplasia - answer:-Irreversible conversion of a cell to a tumorigenic one that grows
uncontrollably. This does not necessarily mean conversion of a cell to a cancerous one.
The term cancer means malignant potential (i.e., capable of metastasis). But benign
tumors such as fibroadenoma and uterine fibroids are still neoplastic. Cervical
intraepithelial neoplasia (CIN) is often reversible, as it is technically dysplasia, despite
the name.
Apoptosis - answer:-Cell death that is programmed and well-controlled; active process;
uses ATP.
Intrinsic pathway - answer:-Activated in response to cell damage/stress/infection;
involves Bax and Bak proteins creating pores in mitochondria, leading to cytochrome c
leakage, apoptosome assembly, caspase activation, and cell death.
Extrinsic pathway - answer:-Activated in response to external signals; involves death
receptors (FAS or TNF receptor) activated by external death ligands (FAS-L or TRAIL),
leading to death-inducing signaling complex (DISC) formation and caspase activation.
Hepatocellular death in hepatitis - answer:-Due to T-cell-mediated apoptosis; direct viral
cytopathicity is incorrect.
DNA ladders of 180bp - answer:-Can be formed during apoptosis, noted in offline
NBME.
Apoptotic cells - answer:-Fragment into smaller apoptotic bodies, which are
phagocytosed.
Menstruation - answer:-Is apoptosis, not atrophy.
Necrosis - answer:-Cell death that is uncontrolled, usually from injury or ischemia; a
passive process that does not use ATP.
Coagulative necrosis - answer:-Cellular architecture is maintained; examples include
myocardial infarction and acute tubular necrosis.
Liquefactive necrosis - answer:-Cellular architecture is not maintained and is dissolved
by hydrolytic enzymes; associated with abscesses and CNS-related conditions.
Caseous necrosis - answer:-Cheese-like necrosis associated with TB, fungal infections,
and Bartonella henselae (cat-scratch disease).
, HY General Pathology Review for
USMLE Questions And Answers 2025
Enzymatic fat necrosis - answer:-Occurs in acute pancreatitis where pancreatic lipases
dissolve surrounding architecture and chelate Ca2+, leading to saponification.
Non-enzymatic fat necrosis - answer:-Occurs due to breast trauma.
Fibrinoid necrosis - answer:-Looks like fibrin but is not; seen in polyarteritis nodosa
affecting small- and medium-sized arteries.
Dry gangrenous necrosis - answer:-Tissue death, usually in limbs, due to interrupted
blood supply; a type of coagulative necrosis.
Wet gangrenous necrosis - answer:-Infective necrosis of limbs; can be a sequela of dry
gangrene.
Fournier gangrene - answer:-Necrosis of perineum/scrotum in advanced diabetes.
Gas gangrenous necrosis - answer:-Caused by C. perfringens secreting a-
toxin/phospholipase that produces CO2 gas within tissues, leading to crepitus/crunching
of necrotic skin.
Cystic medial necrosis - answer:-Necrosis of large arteries with collagen-linking defects,
leading to cyst-like lesions; associated with aortic dissection and aneurysm.
Liquefactive necrosis in CNS - answer:-The answer for necrosis of nervous system
tissue.
Red neurons - answer:-Seen acutely with ischemic infarction of the CNS; characterized
by strong eosinophilic staining with H&E.
Microglia - answer:-Resident macrophages of the CNS that phagocytose necrotic
brain/spinal tissue.
Astrocytes - answer:-Glial cells that proliferate and become a glial scar (gliosis) in
response to CNS injury.
Astrocyte - answer:-Cell responsible for scar formation in CNS.
Wallerian degeneration - answer:-Degradation of an axon/myelin sheath distal to the
site of injury; regrowth occurs at a maximum of 1mm/day.
PNS - answer:-Peripheral Nervous System, where regeneration occurs.
USMLE Questions And Answers 2025
Anaplasia - answer:-Reversion to more immature cell type (i.e., a cell goes from, e.g.,
mature skin cell back to a stem cell). Means high-grade in cancer and poorer prognosis.
Aplasia - answer:-Tissue/organ doesn't develop. DiGeorge syndrome à aplasia of 3rd
and 4th pharyngeal pouches à missing thymus and parathyroid glands à T-cell
deficiency and hypocalcemia/hyperphosphatemia.
Atrophy - answer:-Diminished cell growth/size due to under-stimulation. Shows up on
NBME exam for effect on prostate tissue treated with orchiectomy in the setting of
prostatic adenocarcinoma; ¯ testosterone à ¯ DHT à ¯ prostate stimulation. Testicular
atrophy in the setting of exogenous anabolic steroid use; negative feedback at
hypothalamus/anterior pituitary à ¯ LH secretion à ¯ testicular stimulation. Thyroid
follicular atrophy with exogenous T3/T4 use; negative feedback at
hypothalamus/anterior pituitary à ¯ TSH secretion à ¯ thyroid stimulation. Menopausal
effects on ovaries and endometrium; don't confuse with menses, which are apoptotic.
Dysplasia - answer:-Cellular atypia that is precursor to cancer; cells are not yet
cancerous/tumorigenic. Reversible process; students often erroneously think it is
irreversible. USMLE is not going to ask, 'Is dysplasia irreversible or reversible?' What
they will do is give you, e.g., koilocytes with HPV 16/18 infection, and you need to know
most cases of low- and high-grade squamous epithelial dysplasia are reversible /
spontaneously regress.
Hyperplasia - answer:-Increased cell number. Endometrial hyperplasia due to
unopposed estrogen is highest yield example on USMLE. Anovulatory cycles à no
corpus luteum à no progesterone production à unopposed estrogen à endometrial
hyperplasia à increased risk of endometrial dysplasia and adenocarcinoma. I discuss
these mechanisms in high detail in my Obgyn / Repro PDF. Benign prostatic
hyperplasia (BPH) à older males will have large, hyperplastic prostates due to lifetime of
DHT exposure.
Hypertrophy - answer:-Increased cell size. Highest yield example on USMLE is
ventricular myocardial hypertrophy. High afterload causes concentric hypertrophy; high
preload causes eccentric hypertrophy. I discuss these mechanisms in the Cardio
section and HY Arrows PDF. Skeletal muscle hypertrophy in response to resistance
weight training.
Metaplasia - answer:-One mature cell type becomes another mature cell type;
reversible. Barrett esophagus caused by reflux is highest yield example on USMLE:
non-keratinized stratified squamous epithelium of distal esophagus à intestinal columnar
epithelium (meaning has goblet cells that produce mucous). The stomach doesn't have
goblet cells; it has mucous neck cells, aka foveolar cells.
,HY General Pathology Review for
USMLE Questions And Answers 2025
Neoplasia - answer:-Irreversible conversion of a cell to a tumorigenic one that grows
uncontrollably. This does not necessarily mean conversion of a cell to a cancerous one.
The term cancer means malignant potential (i.e., capable of metastasis). But benign
tumors such as fibroadenoma and uterine fibroids are still neoplastic. Cervical
intraepithelial neoplasia (CIN) is often reversible, as it is technically dysplasia, despite
the name.
Apoptosis - answer:-Cell death that is programmed and well-controlled; active process;
uses ATP.
Intrinsic pathway - answer:-Activated in response to cell damage/stress/infection;
involves Bax and Bak proteins creating pores in mitochondria, leading to cytochrome c
leakage, apoptosome assembly, caspase activation, and cell death.
Extrinsic pathway - answer:-Activated in response to external signals; involves death
receptors (FAS or TNF receptor) activated by external death ligands (FAS-L or TRAIL),
leading to death-inducing signaling complex (DISC) formation and caspase activation.
Hepatocellular death in hepatitis - answer:-Due to T-cell-mediated apoptosis; direct viral
cytopathicity is incorrect.
DNA ladders of 180bp - answer:-Can be formed during apoptosis, noted in offline
NBME.
Apoptotic cells - answer:-Fragment into smaller apoptotic bodies, which are
phagocytosed.
Menstruation - answer:-Is apoptosis, not atrophy.
Necrosis - answer:-Cell death that is uncontrolled, usually from injury or ischemia; a
passive process that does not use ATP.
Coagulative necrosis - answer:-Cellular architecture is maintained; examples include
myocardial infarction and acute tubular necrosis.
Liquefactive necrosis - answer:-Cellular architecture is not maintained and is dissolved
by hydrolytic enzymes; associated with abscesses and CNS-related conditions.
Caseous necrosis - answer:-Cheese-like necrosis associated with TB, fungal infections,
and Bartonella henselae (cat-scratch disease).
, HY General Pathology Review for
USMLE Questions And Answers 2025
Enzymatic fat necrosis - answer:-Occurs in acute pancreatitis where pancreatic lipases
dissolve surrounding architecture and chelate Ca2+, leading to saponification.
Non-enzymatic fat necrosis - answer:-Occurs due to breast trauma.
Fibrinoid necrosis - answer:-Looks like fibrin but is not; seen in polyarteritis nodosa
affecting small- and medium-sized arteries.
Dry gangrenous necrosis - answer:-Tissue death, usually in limbs, due to interrupted
blood supply; a type of coagulative necrosis.
Wet gangrenous necrosis - answer:-Infective necrosis of limbs; can be a sequela of dry
gangrene.
Fournier gangrene - answer:-Necrosis of perineum/scrotum in advanced diabetes.
Gas gangrenous necrosis - answer:-Caused by C. perfringens secreting a-
toxin/phospholipase that produces CO2 gas within tissues, leading to crepitus/crunching
of necrotic skin.
Cystic medial necrosis - answer:-Necrosis of large arteries with collagen-linking defects,
leading to cyst-like lesions; associated with aortic dissection and aneurysm.
Liquefactive necrosis in CNS - answer:-The answer for necrosis of nervous system
tissue.
Red neurons - answer:-Seen acutely with ischemic infarction of the CNS; characterized
by strong eosinophilic staining with H&E.
Microglia - answer:-Resident macrophages of the CNS that phagocytose necrotic
brain/spinal tissue.
Astrocytes - answer:-Glial cells that proliferate and become a glial scar (gliosis) in
response to CNS injury.
Astrocyte - answer:-Cell responsible for scar formation in CNS.
Wallerian degeneration - answer:-Degradation of an axon/myelin sheath distal to the
site of injury; regrowth occurs at a maximum of 1mm/day.
PNS - answer:-Peripheral Nervous System, where regeneration occurs.
