Martin is a 28-year-old young man of Honduran descent, whom you've never met before. He's the boyfriend of a long-term female patient of yours, and has been complaining of right-sided chest pain for the past two weeks.

Martin is thin and healthy-looking, with no previous illness. Approximately 12 days before, he remembers having a violent sneeze, followed by pain on the right side of his chest. It has persisted and gets worse with deep inspiration. There's no cough, shortness of breath, or fever. He doesn't play contact sports or recall any incident of trauma.

On examination, his vital signs are normal. The chest is clear, with evidence of good air entry in all lung fields. There's definite tenderness to palpation of the chest wall on the right side at the mid-axillary line. Both the cardiovascular and abdominal examinations are non-contributory. He seems to have suffered a strain or tear of one of the intercostal muscles, so you advise him to rest, take acetaminophen as required, and return in a week or two if the pain continues.

About 10 days later, Martin's back. You remember being fooled once before by a spontaneous pneumothorax in a thin, young man who had ruptured a bleb, so you order an x-ray of the chest and right ribs, as well as blood work. The imaging report shows a pathologic fracture of the 6th rib, with a suggestion to get a CT scan.

The white blood count is 11.9 x 10⁹ cells/L, with a preponderance of monocytes. Hemoglobin is 146 g/L, and chemistry is normal, including calcium. After the CT scan, the patient is referred to a chest surgeon for a rib biopsy. What's your diagnosis?

What's the diagnosis?