A patient presents to a physician complaining of recurrent episodic diarrhea, triggered by eating too much or drinking alcohol. His wife states that "he turns as red as a beet, stas wheezing, and looks just ghastly" during these episodes. Chest x-ray demonstrates a lung mass. Which of the following would MOST likely be present on biopsy of the lesion?

The patient has carcinoid syndrome, in which vasoactive mediators secreted by carcinoid tumors (typically of the lung or small bowel) produce recurrent diarrhea, flushing, wheezing, and carcinoid hea disease. Although many substances may be produced by these tumors, serotonin is one of the more impoant mediators produced, probably accounting for the observed diarrhea.Bronchioloalveolar carcinomas are not paicularly likely to secrete hormones.Primary and recurrent tuberculosis can be uncommonly associated with finger clubbing, or hyperophic osteopathy, but not with carcinoid syndrome. Ref: Chandrasoma P., Taylor C.R. (1998). Chapter 41. The Intestines: III. Neoplasms. In P. Chandrasoma, C.R. Taylor (Eds), Concise Pathology, 3e.