USMLE Pathology 1 — Questions and Answers
Question 1: A 55-year-old smoker presents with a central lung mass, hypercalcemia, and finger clubbing. Histology shows keratin pearls and intercellular bridges. What is the diagnosis?
- Squamous cell carcinoma (Correct answer)
- Adenocarcinoma
- Small cell carcinoma
- Large cell carcinoma
Correct answer: Squamous cell carcinoma
Squamous cell carcinoma arises centrally, produces PTHrP causing hypercalcemia, and shows keratin pearls with intercellular bridges on histology.
Question 2: Which type of necrosis is characteristic of tuberculosis granulomas?
- Caseous necrosis (Correct answer)
- Liquefactive necrosis
- Coagulative necrosis
- Fat necrosis
Correct answer: Caseous necrosis
Caseous necrosis is characteristic of granulomatous inflammation in TB, producing a cheese-like gross appearance due to incomplete digestion of cellular debris.
Question 3: A patient with SLE has a positive ANA and anti-dsDNA antibodies. Which type of hypersensitivity reaction mediates the kidney damage in lupus nephritis?
- Type III (immune complex-mediated) (Correct answer)
- Type II (antibody-mediated cytotoxicity)
- Type I (IgE-mediated)
- Type IV (cell-mediated)
Correct answer: Type III (immune complex-mediated)
Lupus nephritis is caused by deposition of immune complexes (dsDNA-anti-dsDNA) in the glomerular basement membrane, activating complement and causing type III hypersensitivity injury.
Question 4: Which tumor marker is elevated in hepatocellular carcinoma?
- Alpha-fetoprotein (AFP) (Correct answer)
- CEA
- CA 19-9
- PSA
Correct answer: Alpha-fetoprotein (AFP)
AFP is the primary tumor marker for hepatocellular carcinoma (HCC) and is also elevated in yolk sac tumors and in normal fetal liver.
Question 5: A 30-year-old woman has a breast mass that moves freely, is rubbery, and has well-defined borders. No lymph node involvement. What is the most likely diagnosis?
- Fibroadenoma (Correct answer)
- Ductal carcinoma in situ
- Infiltrating ductal carcinoma
- Phyllodes tumor
Correct answer: Fibroadenoma
Fibroadenoma is the most common benign breast tumor in young women, presenting as a well-circumscribed, rubbery, freely movable mass with no lymph node involvement.
Question 6: A patient with chronic myeloid leukemia (CML) has the Philadelphia chromosome. Which genetic translocation produces this?
- t(9;22) (Correct answer)
- t(8;14)
- t(14;18)
- t(15;17)
Correct answer: t(9;22)
CML is characterized by t(9;22), creating the BCR-ABL fusion gene on the Philadelphia chromosome, which encodes a constitutively active tyrosine kinase.
USMLE Pathology 1
A 55-year-old smoker presents with a central lung mass, hypercalcemia, and finger clubbing.
Histology shows keratin pearls and intercellular bridges.
What is the diagnosis?