RACS question of the week.

A 22-year-old woman has an 11 cm solitary liver mass. Computed tomography shows a lobulated, heterogeneous lesion with a central scar containing a focus of calcification. She does not drink alcohol, hepatitis B and C serology is negative, the background liver is normal, and her alpha-fetoprotein is normal. Biopsy shows large polygonal cells with abundant granular eosinophilic cytoplasm and prominent nucleoli, in cords separated by bands of dense collagen; the cells are positive for CK7 and CD68. Which diagnosis is most likely?

A 45-year-old man hit his head in a fall from his bicycle. He now has vertical double vision that is worst when he reads. Cover testing shows that the right eye sits higher than the left. The vertical deviation increases when he looks to the left and when his head is tilted towards his right shoulder. Which cranial nerve is injured?

A 40-year-old man is intubated one hour after rescue from an enclosed house fire. On an FiO2 of 0.5 his PaO2 is 210 mmHg and his carboxyhaemoglobin is 4%. His cardiac output is normal, his lactate is 11 mmol/L and his central venous oxygen saturation is 88%. Which process best explains his lactic acidosis?

A 19-year-old man has a laparotomy for a jejunal intussusception. The lead point is a 3 cm pedunculated polyp, and several smaller polyps are palpable elsewhere in the jejunum. Histology shows a hamartomatous polyp with branching bands of smooth muscle extending from the muscularis mucosae into its core, covered by normal-appearing small bowel mucosa without dysplasia. A germline mutation in which gene is most likely?