NBME Practice MCB Questions and Answers for the Latest Edition

A 2 year old girl who is exposed to the sun has progressive development of dryness of the skin, excessive freckling, and keratoses. Skin fibroblasts cultured from this child are most likely to be defective in which of the following? Nuclear excision repair of pyrimidine dimers a 65 year old man has a radical prostacetomy and lymph node dissection for adenocarcinoma of the prostate. which of the following features is involved in the grading of this neoplasm Tumor size A man with a fair complexion develops an ulcerated nodule on his face after prolonged exposure to sunlight. Examination of tissue obtained on excision of the nodule shows invasive squamous cell carcinoma. Which of the following types of DNA damage is most likely responsible for this leason? Pyrimidine dimers A 45 year old woman with cancer is undergoing an intensive 2 week course of chemotherapy with vinblastine. Which of the following changes is most likely to occur by the end of this treatment? Decreased number of neutrophils - vinblastin mechanism is to bind microtubular proteins in the mitotic spindle, thereby preventing cell division during metaphase. (anaphase promoting complex inhibitor) An 11 year old boy has had pain in his right mid thigh for 2 weeks. Physical examination shows an area of warmth and tenderness around an ill defined mass. X ray of the femure shows a solitary mid diaphyseal osteolytic lesion with permeative margins. The lesion is surrounded by concentric layers of reactive bone. Tissue obtained on biosy of the mass is composed of poorly differentiated sheets of small, uniform, hyperchromatic cells with a very high nuclear cytoplasmic ratio, scant stroma, and no visible matrix. Which of the following is the most likely diagnosis? Ewing sarcoma - Ewing sarcoma is a type of cancer that may be a bone sarcoma or a softtissue sarcoma. Symptoms may include swelling and pain at the site of the tumor, fever, and a bone fracture. a 55 year old woman with colon cancer and a healthy 55 year old woman are participating in a study of colon cancer. malignant cells are obtained from the tumor in the affect patient, and normal colonic epithelial cells are procured from the healthy subject. After both cell tpyes are treated with transforming growth factor B, the number of normal cells decreases whereas the number of tumor cells remains unchanged. The tumor cells most likely express a mutation that inhibits which of the following physiological processes. Apoptosis A 10 month old boy has an abdominal mass noted during a routine physical examination. Abdominal ultrasonography shows a 10 cm solid mass on the upper pole of the left kidney. Angiographically, the mass is hypervascular. Which of the following is the most likely diagnosis? Nephroblastoma (Wilms Tumor) A 52 year old man comes to the physician because of a 3 month hisotry of epigastric abdominal painl; he used to live in japan, is a smokr and drinks three to four glasses of wine daily. Physical exam shows epigastric tenderness. Upper gastrointestinal endoscopy shows a 4 cm ulcer in the stomach. Examination of a biosy specimen of the lesion confirms adenocarinoma. Which of the following is the strongest predisposing risk factor for the patient's condition? Diet An investigator conducts a study of the molecular basis of von Hippel lindau disease, specifically the role of the VHL protein in the disease process. The protein forms part of a ubiquitin ligase complex (E3) that targets hypoxia- inducible factor -1. The pathway is shown in the diagram. Step IV most likely involves which of the following organelles? Proteasome A 28 year old man is diagnosed with advanced testicular cancer. Combination chemotherapy is being considered. Cisplatin is included in the regimen because of its effect on which of the following? DNA A study is conducted of breast cancer cell invasion of surrounding tissues and metastasis. Two breast cancer cell lines, in the presence and absence of macrophages are analyzed. The macrophages are found to secrete a protein that is essential for invasion and metastasis. This protein is most likely which of the following? Metalloproteinases (MMPS