Three high-yield USMLE Step 1 pathology questions: esophageal rupture after vomiting, a lymphoma with CD15 and CD30, and the most common malignant brain tumor in adults. Pick your answer first, then open the explanation.
Question 1: Chest pain after vomiting with subcutaneous emphysema
An alcoholic patient presents with sudden chest pain, cough and shortness of breath after repeated episodes of retching and vomiting. Examination reveals subcutaneous emphysema. Which of the following is the most likely diagnosis?
A. Boerhaave syndrome B. Mallory-Weiss tear C. Myocardial infarction D. Rupture of esophageal varices
Correct answer: A. Boerhaave syndrome
Boerhaave syndrome is a transmural (full-thickness) rupture of the distal esophagus caused by a sudden rise in pressure during forceful vomiting. Air escapes into the mediastinum, causing pneumomediastinum and subcutaneous emphysema. It is a surgical emergency.
Why the other options are wrong:
Mallory-Weiss tear is a mucosal (not transmural) tear at the gastroesophageal junction; it causes painless hematemesis without air in the tissues.
Myocardial infarction does not cause subcutaneous emphysema.
Ruptured esophageal varices cause massive painless hematemesis in a patient with portal hypertension.
High-yield: Classic signs: Mackler triad (vomiting, lower chest pain, subcutaneous emphysema) and Hamman sign (crunching sound with the heartbeat). Diagnose with a water-soluble contrast esophagram or CT.
Question 2: Lymph node biopsy with CD15 and CD30 positive cells
A 34-year-old man presents with fatigue, chills and weight loss for the last 2 months. Examination reveals enlarged, non-tender cervical lymph nodes. A lymph node biopsy shows cells expressing CD15 and CD30. Which of the following is the most likely diagnosis?
A. Acute lymphoblastic leukemia B. Chronic lymphocytic leukemia C. Hodgkin lymphoma D. Non-Hodgkin lymphoma
Correct answer: C. Hodgkin lymphoma
Hodgkin lymphoma is characterized by Reed-Sternberg cells (large “owl-eye” cells of B-cell origin) that are CD15+ and CD30+. It typically presents with painless cervical lymphadenopathy and B symptoms (fever, night sweats, weight loss) and has a bimodal age distribution.
Why the other options are wrong:
ALL affects mainly children and shows TdT+ lymphoblasts in the bone marrow.
CLL affects older adults; smudge cells, CD5+ and CD20+ B cells.
Non-Hodgkin lymphomas lack Reed-Sternberg cells and usually express B-cell (CD19, CD20) or T-cell markers.
High-yield: The nodular sclerosis subtype is the most common Hodgkin lymphoma, often in young women with a mediastinal mass. Pain in lymph nodes after drinking alcohol is a classic clue.
Question 3: Most common malignant primary brain tumor in adults
Which one of the following is the most common and most malignant primary brain tumor of the cerebral hemispheres in adults?
A. Astrocytoma (low grade) B. Glioblastoma multiforme C. Lymphosarcoma D. Meningioma
Correct answer: B. Glioblastoma multiforme
Glioblastoma (grade 4 astrocytoma) is the most common malignant primary brain tumor in adults, usually after age 50. It infiltrates surrounding brain and can cross the corpus callosum (“butterfly glioma”). Histology shows pseudopalisading necrosis and vascular proliferation; tumor cells are GFAP positive.
Why the other options are wrong:
Low-grade astrocytoma grows slowly and is less malignant.
Lymphosarcoma (lymphoma) of the brain is less common and is linked to HIV/immunosuppression.
Meningioma is the most common benign brain tumor; it arises from arachnoid cells and shows psammoma bodies.
High-yield: Median survival of glioblastoma is only about 15 months despite surgery, radiation and temozolomide.
