Why does Warfarin induce a transient hypercoagulable state during the first 24–48 hours of administration?

Protein C has a very short half-life (~6 hours) compared to procoagulant factors (e.g., prothrombin ~60 hours). Early Protein C depletion leads to unopposed coagulation before procoagulant factors fall, risking Warfarin-induced skin necrosis unless bridged with heparin.

What serum tumor marker is elevated in Pancreatic adenocarcinoma and cholangiocarcinoma?

CA 19-9 (Carbohydrate Antigen 19-9). Correlates with tumor burden and response to chemotherapy/surgical resection in pancreatic adenocarcinoma.

What is the function of the Retinoblastoma (Rb) protein at the G1 to S phase checkpoint?

Hypophosphorylated Rb binds and sequesters the E2F transcription factor, blocking transcription of S-phase genes. Cyclin D/CDK4/6 hyperphosphorylates Rb, releasing E2F and driving entry into S phase.

What chromosomal translocation is pathognomonic for Burkitt lymphoma, and what oncogene is upregulated?

t(8;14)(q24;q32), placing the c-MYC proto-oncogene under the control of the highly active immunoglobulin heavy chain (IGH) promoter on chromosome 14, driving constitutive cellular proliferation with a 'starry sky' histology.

What chromosomal translocation and fusion protein define Chronic Myelogenous Leukemia (CML)?

t(9;22)(q34;q11), creating the Philadelphia chromosome with BCR-ABL1 fusion gene encoding a constitutively active tyrosine kinase; treated with Imatinib.

What serum marker is used to monitor recurrence in Colorectal Carcinoma after resection?

Carcinoembryonic Antigen (CEA). Useful for monitoring therapeutic response and detecting disease recurrence, but not for initial screening.

What is the immediate management for a patient diagnosed with Heparin-Induced Thrombocytopenia?

Immediately discontinue all heparin products (including flushes) and initiate non-heparin anticoagulation with a direct thrombin inhibitor (Argatroban, Bivalirudin) or Fondaparinux. Warfarin is contraindicated initially due to risk of venous limb gangrene.

What is the molecular defect in Hemophilia A versus Hemophilia B, their inheritance, and their coagulation profile?

Hemophilia A: Factor VIII deficiency. Hemophilia B (Christmas disease): Factor IX deficiency. Both are X-linked recessive. Both show isolated prolonged aPTT with normal PT, normal platelet count, and normal bleeding time.

What tumor marker is produced by Choriocarcinoma and Hydatidiform moles, as well as testicular seminomas/non-seminomas?

Beta-hCG (human chorionic gonadotropin). Produced by syncytiotrophoblastic cells; can cause hyperthyroidism due to homology with TSH.

What is the function of the KRAS proto-oncogene and what downstream signaling pathway does it belong to?

GTPase that acts as an intracellular molecular switch in the EGFR/MAPK signaling cascade. Activating point mutations (common in colon, pancreatic, and lung cancers) prevent GTP hydrolysis, causing permanent downstream signaling; resistant to anti-EGFR mAbs (Cetuximab).

What type of necrosis is pathognomonic for ischemic cerebral infarction?

Liquefactive necrosis: Brain tissue hydrolytic enzymes and microglial digestion liquefy dead parenchymal tissue into a cystic cavity, unlike coagulative necrosis seen in solid organs.

What translocation characterizes Follicular Lymphoma, and what anti-apoptotic protein is overexpressed?

t(14;18)(q32;q21), placing the BCL-2 oncogene under the control of the immunoglobulin heavy chain (IGH) locus, overexpressing Bcl-2 which blocks apoptotic mitochondrial cytochrome c release.

What is the most common inherited cause of hypercoagulability (thrombophilia) in Caucasian populations?

Factor V Leiden mutation (G1691A substitution replacing arginine with glutamine at position 506). Makes Factor Va resistant to inactivation by Activated Protein C (APC).

What is the most common inherited bleeding disorder, and what laboratory findings are characteristic?

von Willebrand Disease (vWD; usually autosomal dominant). Causes impaired platelet adhesion and stabilization of Factor VIII. Labs: Prolonged bleeding time/PFA-100, normal or prolonged aPTT (due to low Factor VIII), normal PT, and abnormal Ristocetin cofactor assay.

What enzyme deficiency causes Thrombotic Thrombocytopenic Purpura (TTP), and what is the classic clinical pentad?

Severe deficiency or autoantibody against ADAMTS13 (vWF-cleaving metalloprotease), causing ultra-large vWF multimers that shear platelets and RBCs. Pentad: Thrombocytopenia, Microangiopathic hemolytic anemia (schistocytes), Neurologic symptoms, Renal dysfunction, and Fever ('FAT RN').

What translocation is diagnostic of Ewing Sarcoma, and what is the typical histological appearance?

t(11;22)(q24;q12), creating the EWS-FLI1 fusion transcript. Histology demonstrates sheets of small round blue cells with Homer-Wright pseudorosettes and positive CD99 staining.

What is the definition of Dysplasia and how does it differ from Metaplasia?

Metaplasia: Reversible reprogramming of one differentiated adult cell type into another (e.g., Barrett esophagus: squamous to columnar). Dysplasia: Disordered growth with loss of cellular uniformity, architecture, pleomorphism, and hyperchromatic nuclei, considered premalignant.

What translocation is characteristic of Mantle Cell Lymphoma, and what cell cycle protein is overexpressed?

t(11;14)(q13;q32), juxtaposing the Cyclin D1 (CCND1) gene with the Ig heavy chain promoter, causing constitutive Cyclin D1 overexpression and driving G1 to S phase transition.

What is the Prothrombin G20210A mutation and how does it predispose to venous thromboembolism?

A point mutation in the 3' untranslated region (UTR) of the prothrombin gene that increases mRNA stability and translation, resulting in elevated plasma prothrombin levels and a ~2- to 3-fold higher risk of VTE.

What is the role of p53 in cell cycle arrest and apoptosis, and what syndrome arises from germline TP53 mutations?

p53 arrests the cell cycle at G1/S transition by upregulating p21 (CDK inhibitor) in response to DNA damage, or induces apoptosis via BAX/BAK. Germline TP53 mutation causes Li-Fraumeni syndrome (SBLA: Sarcoma, Breast, Leukemia, Adrenal tumors).

What translocation defines Acute Promyelocytic Leukemia (APL / AML M3), and what targeted therapy induces remission?

t(15;17)(q24;q21), creating PML-RARA fusion which blocks myeloid differentiation at the promyelocyte stage. Treated with All-trans retinoic acid (ATRA) and Arsenic trioxide, preventing fatal DIC.

What are the three factors in Virchow's Triad of thrombosis?

1. Endothelial injury/damage; 2. Stasis or turbulent blood flow; 3. Hypercoagulability of blood.

What tumor marker is used to monitor non-seminomatous germ cell tumors and Hepatocellular Carcinoma (HCC)?

Alpha-fetoprotein (AFP). Markedly elevated in yolk sac (endodermal sinus) tumors and hepatocellular carcinoma; also elevated in cirrhosis and ataxia-telangiectasia.

What serum tumor marker is elevated in Medullary Thyroid Carcinoma?

Calcitonin, secreted by neoplastic parafollicular C cells (associated with MEN 2A and MEN 2B syndromes due to RET proto-oncogene mutations).

What are the coagulation profile differences between Disseminated Intravascular Coagulation (DIC) and TTP?

DIC: Clotting cascade is consumptively activated; Prothrombin Time (PT) and Activated Partial Thromboplastin Time (aPTT) are prolonged, fibrinogen is low, and D-dimer is markedly elevated. TTP: Platelet-only consumption; PT and aPTT are completely NORMAL, with normal fibrinogen.

What is Knudson's 'two-hit' hypothesis and which tumor suppressor gene served as the classic paradigm?

Both alleles of a tumor suppressor gene must be inactivated for oncogenesis. In hereditary retinoblastoma (RB1 gene on 13q14), one allele is mutated in the germline ('first hit') and a somatic mutation disables the second allele ('second hit').

What morphological and biochemical features differentiate Apoptosis from Necrosis?

Apoptosis: Programmed, ATP-dependent, cellular shrinkage, intact cell membrane, pyknosis, karyorrhexis, apoptotic bodies, no inflammatory reaction. Necrosis: Unregulated, ATP-depleted, cellular swelling, disrupted membrane, nuclear lysis, marked acute inflammation.

What immunohistochemical marker stains positive in malignant melanoma, and what other markers are sensitive?

S100 (neural crest origin), HMB-45, and Melan-A (MART-1).

What serum tumor marker is used to monitor epithelial Ovarian cancer recurrence?

CA 125 (Cancer Antigen 125). Used for post-treatment monitoring of serous ovarian carcinoma (not recommended for general population screening due to low specificity in premenopausal women).

What immunohistochemical marker stains positive in neoplasms of mesenchymal origin (e.g., sarcomas)?

Vimentin (intermediate filament characteristic of mesenchymal tissue, distinguishing sarcomas from carcinomas which stain positive for cytokeratins).

What is the pathophysiology of Heparin-Induced Thrombocytopenia (HIT Type 2)?

IgG antibodies form against Heparin-Platelet Factor 4 (PF4) complexes. The Fc portion of the antibody cross-links Fc-gamma-RIIa receptors on platelets, causing massive platelet activation, paradoxically leading to widespread arterial and venous thrombosis with moderate thrombocytopenia.

What is the mechanism of action of Heparin versus Warfarin on the coagulation cascade?

Heparin: Binds antithrombin III (ATIII) causing a conformational change that accelerates its inactivation of Thrombin (IIa) and Factor Xa (monitored via aPTT). Warfarin: Inhibits Vitamin K epoxide reductase (VKORC1), blocking gamma-carboxylation of Factors II, VII, IX, X and Proteins C and S (monitored via PT/INR).

USMLE Step 1 & 2 — General Pathology, Neoplasia, Hemostasis & Oncologic Markers

Cellular adaptation, cell injury/death, tumor genetics, hallmarks of cancer, coagulation cascades, thrombophilia, and oncologic diagnostic markers.

Level: intermediate
Languages: en → en
Cards: 32
Markdown: USMLE Step 1 & 2 — General Pathology, Neoplasia, Hemostasis & Oncologic Markers (.md)

Flashcards (32)

#	Front (Term / Question)	Back (Definition / Answer)
1	Why does Warfarin induce a transient hypercoagulable state during the first 24–48 hours of administration?	Protein C has a very short half-life (~6 hours) compared to procoagulant factors (e.g., prothrombin ~60 hours). Early Protein C depletion leads to unopposed coagulation before procoagulant factors fall, risking Warfarin-induced skin necrosis unless bridged with heparin.
2	What serum tumor marker is elevated in Pancreatic adenocarcinoma and cholangiocarcinoma?	CA 19-9 (Carbohydrate Antigen 19-9). Correlates with tumor burden and response to chemotherapy/surgical resection in pancreatic adenocarcinoma.
3	What is the function of the Retinoblastoma (Rb) protein at the G1 to S phase checkpoint?	Hypophosphorylated Rb binds and sequesters the E2F transcription factor, blocking transcription of S-phase genes. Cyclin D/CDK4/6 hyperphosphorylates Rb, releasing E2F and driving entry into S phase.
4	What chromosomal translocation is pathognomonic for Burkitt lymphoma, and what oncogene is upregulated?	t(8;14)(q24;q32), placing the c-MYC proto-oncogene under the control of the highly active immunoglobulin heavy chain (IGH) promoter on chromosome 14, driving constitutive cellular proliferation with a 'starry sky' histology.
5	What chromosomal translocation and fusion protein define Chronic Myelogenous Leukemia (CML)?	t(9;22)(q34;q11), creating the Philadelphia chromosome with BCR-ABL1 fusion gene encoding a constitutively active tyrosine kinase; treated with Imatinib.
6	What serum marker is used to monitor recurrence in Colorectal Carcinoma after resection?	Carcinoembryonic Antigen (CEA). Useful for monitoring therapeutic response and detecting disease recurrence, but not for initial screening.
7	What is the immediate management for a patient diagnosed with Heparin-Induced Thrombocytopenia?	Immediately discontinue all heparin products (including flushes) and initiate non-heparin anticoagulation with a direct thrombin inhibitor (Argatroban, Bivalirudin) or Fondaparinux. Warfarin is contraindicated initially due to risk of venous limb gangrene.
8	What is the molecular defect in Hemophilia A versus Hemophilia B, their inheritance, and their coagulation profile?	Hemophilia A: Factor VIII deficiency. Hemophilia B (Christmas disease): Factor IX deficiency. Both are X-linked recessive. Both show isolated prolonged aPTT with normal PT, normal platelet count, and normal bleeding time.
9	What tumor marker is produced by Choriocarcinoma and Hydatidiform moles, as well as testicular seminomas/non-seminomas?	Beta-hCG (human chorionic gonadotropin). Produced by syncytiotrophoblastic cells; can cause hyperthyroidism due to homology with TSH.
10	What is the function of the KRAS proto-oncogene and what downstream signaling pathway does it belong to?	GTPase that acts as an intracellular molecular switch in the EGFR/MAPK signaling cascade. Activating point mutations (common in colon, pancreatic, and lung cancers) prevent GTP hydrolysis, causing permanent downstream signaling; resistant to anti-EGFR mAbs (Cetuximab).
11	What type of necrosis is pathognomonic for ischemic cerebral infarction?	Liquefactive necrosis: Brain tissue hydrolytic enzymes and microglial digestion liquefy dead parenchymal tissue into a cystic cavity, unlike coagulative necrosis seen in solid organs.
12	What translocation characterizes Follicular Lymphoma, and what anti-apoptotic protein is overexpressed?	t(14;18)(q32;q21), placing the BCL-2 oncogene under the control of the immunoglobulin heavy chain (IGH) locus, overexpressing Bcl-2 which blocks apoptotic mitochondrial cytochrome c release.
13	What is the most common inherited cause of hypercoagulability (thrombophilia) in Caucasian populations?	Factor V Leiden mutation (G1691A substitution replacing arginine with glutamine at position 506). Makes Factor Va resistant to inactivation by Activated Protein C (APC).
14	What is the most common inherited bleeding disorder, and what laboratory findings are characteristic?	von Willebrand Disease (vWD; usually autosomal dominant). Causes impaired platelet adhesion and stabilization of Factor VIII. Labs: Prolonged bleeding time/PFA-100, normal or prolonged aPTT (due to low Factor VIII), normal PT, and abnormal Ristocetin cofactor assay.
15	What enzyme deficiency causes Thrombotic Thrombocytopenic Purpura (TTP), and what is the classic clinical pentad?	Severe deficiency or autoantibody against ADAMTS13 (vWF-cleaving metalloprotease), causing ultra-large vWF multimers that shear platelets and RBCs. Pentad: Thrombocytopenia, Microangiopathic hemolytic anemia (schistocytes), Neurologic symptoms, Renal dysfunction, and Fever ('FAT RN').
16	What translocation is diagnostic of Ewing Sarcoma, and what is the typical histological appearance?	t(11;22)(q24;q12), creating the EWS-FLI1 fusion transcript. Histology demonstrates sheets of small round blue cells with Homer-Wright pseudorosettes and positive CD99 staining.
17	What is the definition of Dysplasia and how does it differ from Metaplasia?	Metaplasia: Reversible reprogramming of one differentiated adult cell type into another (e.g., Barrett esophagus: squamous to columnar). Dysplasia: Disordered growth with loss of cellular uniformity, architecture, pleomorphism, and hyperchromatic nuclei, considered premalignant.
18	What translocation is characteristic of Mantle Cell Lymphoma, and what cell cycle protein is overexpressed?	t(11;14)(q13;q32), juxtaposing the Cyclin D1 (CCND1) gene with the Ig heavy chain promoter, causing constitutive Cyclin D1 overexpression and driving G1 to S phase transition.
19	What is the Prothrombin G20210A mutation and how does it predispose to venous thromboembolism?	A point mutation in the 3' untranslated region (UTR) of the prothrombin gene that increases mRNA stability and translation, resulting in elevated plasma prothrombin levels and a ~2- to 3-fold higher risk of VTE.
20	What is the role of p53 in cell cycle arrest and apoptosis, and what syndrome arises from germline TP53 mutations?	p53 arrests the cell cycle at G1/S transition by upregulating p21 (CDK inhibitor) in response to DNA damage, or induces apoptosis via BAX/BAK. Germline TP53 mutation causes Li-Fraumeni syndrome (SBLA: Sarcoma, Breast, Leukemia, Adrenal tumors).
21	What translocation defines Acute Promyelocytic Leukemia (APL / AML M3), and what targeted therapy induces remission?	t(15;17)(q24;q21), creating PML-RARA fusion which blocks myeloid differentiation at the promyelocyte stage. Treated with All-trans retinoic acid (ATRA) and Arsenic trioxide, preventing fatal DIC.
22	What are the three factors in Virchow's Triad of thrombosis?	1. Endothelial injury/damage; 2. Stasis or turbulent blood flow; 3. Hypercoagulability of blood.
23	What tumor marker is used to monitor non-seminomatous germ cell tumors and Hepatocellular Carcinoma (HCC)?	Alpha-fetoprotein (AFP). Markedly elevated in yolk sac (endodermal sinus) tumors and hepatocellular carcinoma; also elevated in cirrhosis and ataxia-telangiectasia.
24	What serum tumor marker is elevated in Medullary Thyroid Carcinoma?	Calcitonin, secreted by neoplastic parafollicular C cells (associated with MEN 2A and MEN 2B syndromes due to RET proto-oncogene mutations).
25	What are the coagulation profile differences between Disseminated Intravascular Coagulation (DIC) and TTP?	DIC: Clotting cascade is consumptively activated; Prothrombin Time (PT) and Activated Partial Thromboplastin Time (aPTT) are prolonged, fibrinogen is low, and D-dimer is markedly elevated. TTP: Platelet-only consumption; PT and aPTT are completely NORMAL, with normal fibrinogen.
26	What is Knudson's 'two-hit' hypothesis and which tumor suppressor gene served as the classic paradigm?	Both alleles of a tumor suppressor gene must be inactivated for oncogenesis. In hereditary retinoblastoma (RB1 gene on 13q14), one allele is mutated in the germline ('first hit') and a somatic mutation disables the second allele ('second hit').
27	What morphological and biochemical features differentiate Apoptosis from Necrosis?	Apoptosis: Programmed, ATP-dependent, cellular shrinkage, intact cell membrane, pyknosis, karyorrhexis, apoptotic bodies, no inflammatory reaction. Necrosis: Unregulated, ATP-depleted, cellular swelling, disrupted membrane, nuclear lysis, marked acute inflammation.
28	What immunohistochemical marker stains positive in malignant melanoma, and what other markers are sensitive?	S100 (neural crest origin), HMB-45, and Melan-A (MART-1).
29	What serum tumor marker is used to monitor epithelial Ovarian cancer recurrence?	CA 125 (Cancer Antigen 125). Used for post-treatment monitoring of serous ovarian carcinoma (not recommended for general population screening due to low specificity in premenopausal women).
30	What immunohistochemical marker stains positive in neoplasms of mesenchymal origin (e.g., sarcomas)?	Vimentin (intermediate filament characteristic of mesenchymal tissue, distinguishing sarcomas from carcinomas which stain positive for cytokeratins).
31	What is the pathophysiology of Heparin-Induced Thrombocytopenia (HIT Type 2)?	IgG antibodies form against Heparin-Platelet Factor 4 (PF4) complexes. The Fc portion of the antibody cross-links Fc-gamma-RIIa receptors on platelets, causing massive platelet activation, paradoxically leading to widespread arterial and venous thrombosis with moderate thrombocytopenia.
32	What is the mechanism of action of Heparin versus Warfarin on the coagulation cascade?	Heparin: Binds antithrombin III (ATIII) causing a conformational change that accelerates its inactivation of Thrombin (IIa) and Factor Xa (monitored via aPTT). Warfarin: Inhibits Vitamin K epoxide reductase (VKORC1), blocking gamma-carboxylation of Factors II, VII, IX, X and Proteins C and S (monitored via PT/INR).