NBME Pathology 4

Question 1

An autopsy of a 68-year-old man with dementia shows senile plaques and neurofibrillary tangles. Which protein forms the core of senile plaques?

Accepted Answer

Amyloid-beta (Abeta42)

Answer

Senile (neuritic) plaques in Alzheimer disease are composed of extracellular amyloid-beta peptide (predominantly Abeta42) derived from APP cleavage.

Question 2

A 4-year-old child has a Wilms tumor. Which embryonic tissue fails to differentiate properly, leading to this tumor?

Accepted Answer

Metanephric blastema (nephrogenic rests)

Answer

Wilms tumor (nephroblastoma) arises from persistence of nephrogenic rests — foci of metanephric blastema that fail to differentiate into normal nephrons.

Question 3

A 58-year-old woman undergoes a mastectomy. Histology shows invasive carcinoma with Indian file (single-file) growth pattern and absence of cohesion due to loss of which protein?

Accepted Answer

E-cadherin

Answer

Invasive lobular carcinoma is characterized by single-file tumor cells due to loss of E-cadherin expression from CDH1 mutation or promoter methylation.

Question 4

A 72-year-old man has progressive dyspnea. Spirometry shows FEV1/FVC = 0.55 (reduced) with increased TLC and RV. CT shows panacinar emphysema predominantly in lower lobes. What is the underlying deficiency?

Accepted Answer

Alpha-1 antitrypsin (AAT)

Answer

Alpha-1 antitrypsin deficiency causes panacinar emphysema predominantly in the lung bases because uninhibited neutrophil elastase destroys alveolar walls.

Question 5

A 33-year-old man with ulcerative colitis for 10 years has cholestatic jaundice and pruritus. ERCP shows 'beaded' intrahepatic and extrahepatic bile ducts. What is the diagnosis?

Accepted Answer

Primary sclerosing cholangitis (PSC)

Answer

PSC causes multifocal biliary strictures producing the 'beaded' appearance on cholangiography and is strongly associated with IBD, especially UC.

NBME Practice Test

NBME Practice Test

NBME Pathology 4