WBR0630

Author	[[PageAuthor::Yazan Daaboul, M.D. (Reviewed by Serge Korjian)]]
Exam Type	ExamType::USMLE Step 1
Main Category	MainCategory::Pathology
Sub Category	SubCategory::Gastrointestinal
Prompt	[[Prompt::A 58-year-old man presents to the outpatient clinic with compaints of episodic diarrhea, cutaneous flushing, and dyspnea. Cardiac auscultation is remarkable for a holosystolic, high-pitched blowing murmur heard best at the apex and radiates to the axillary region. Pulmonary auscultation is remarkable for diffuse, bilateral wheezing. Work-up reveals high concentration of urinary 5-hydroxyindoleacetic acid. Which of the following characterizes the appearance of the patient's disease under electron microscopy?]]
Answer A	AnswerA::Cells that contain membrane-bound granules secreting biogenic amines
Answer A Explanation	AnswerAExp::Carcinoid tumors are characterized by the presence of membrane-bound neurosecretory granules that secrete hormones and biogenic amines.
Answer B	AnswerB::Deposits of immune complexes that contain aberrant antibodies
Answer B Explanation	[[AnswerBExp::IgA nephropathy is characterized by the deposition of aberrant IgA1 antibodies. The clinical syndrome of IgA nephropathy is commonly a nephritic syndrome in a young, otherwise healthy patient, with a concurrent history of respiratory or gastrointestinal tract infection. Carcinoid tumors are not related to IgA nephropathy.]]
Answer C	AnswerC::Thyrotrophs with indented nuclei associated with large nucleoli and long cytoplasmic processes.
Answer C Explanation	[[AnswerCExp::Thyrotroph ademonas of the pituitary are characterized by nuclei that are indented associated with large nucleoli and long cytoplasmic processes. Thyrotroph adenomas may present with symptoms of thyrotoxicosis. Urinary 5-HIAA is not typically seen in such adenomas]]
Answer D	AnswerD::Neurosecretory granules around the Golgi complexes that contain vasoactive intestinal polypeptide
Answer D Explanation	AnswerDExp::VIPomas are gastrointestinal neuroendocrine tumors that are characterized by neurosecretory cells that secrete vasoactive intestinal polypeptide (VIP).
Answer E	AnswerE::Cells with granules containing enzymes that cleave angiotensinogen
Answer E Explanation	[[AnswerEExp::Renin-secreting tumors, usually juxtaglomuelar cell tumors, are characterized by the presence of cells that contain granules that have renin, an enzyme that cleaves angiotensinogen into angiotensin I. Hypertension is a common presentation for renin-secreting tumors.]]
Right Answer	RightAnswer::A
Explanation	[[Explanation::Carcinoid tumors are neuroendocrine serotonin-secreting tumors arising from the Kulchitsky cells in the crypts of Liberkuhn. They are commonly present in the GI tract and grow as nodules in the submucosa, especially in the appendix, ileum, and rectum. Patients typically have high levels of urinary 5-hydroxyindoleacetic acid (5-HIAA), a by-product of serotonin. Carcinoid tumors may present at virtually any age; the median age of diagnosis is in the range of 55-65 years of age. Carcinoid tumors may remain asymptomatic in the majority of cases. Symptoms usually arise in the case of metastasis beyond the GI tract, when the liver is unable to metabolize the secreted serotonin. Excess serotonin is responsible for the non-specific symptoms that often occur late in the disease, including diarrhea in more than 80% of the cases. Other common symptoms are cutaneous flushing, erythema, cyanosis, dyspnea due to bronchospasm, abdominal pain, and right-sided cardiac valvulopathy and heart failure. When symptoms become present, carcinoid tumors are then called "carcinoid syndrome". Diagnosis is often difficult, since the tumor may not be easily visualized on routine imaging techniques, which are best at identifying metastasized tumors. Small bowel series may be helpful in diagnosing early carcinoid tumors. Pathological findings, including electron microscopy, are needed to visualize characteristic findings of carcinoid tumors, which are cells that contain secretory granules containing serotonin. Treatment is generally by resection of tumor and pharmacologic therapy, including somatostatin. Prognosis depends on the location, pathological findings of the tumor, and metastasis. Small localized tumors have excellent prognosis with 90% 5-year survival rate. Diagnosis and treatment must take into consideration the probability of metastasis. Educational Objective: Carcinoid syndrome is characterized by diarrhea, cutaneous flushing, right-sided cardiac valvulopathy, and pulmonary wheezing. Patients have elevated levels of urinary 5-HIAA. On electron microscopy, carcnoid tumors have cells that contain membrane-bound granules that secrete serotonin. References: Ha J, Tan WA. Gastrointestinal carcinoid tumors: a review. J Gastroint Dig Syst. 2012; 2(2):107-14 Kulke MH, Mayer RJ. Carcinoid tumors. N Engl J Med. 1999; 340(11):858-68]]
Approved	Approved::Yes
Keyword	WBRKeyword::Carcinoid tumor, WBRKeyword::Carcinoid syndrome, WBRKeyword::Dyspnea, WBRKeyword::Wheezing, WBRKeyword::Diarrhea, WBRKeyword::5-HIAA, WBRKeyword::HIAA, WBRKeyword::Hydroxyindoleacetic acid, WBRKeyword::Serotonin, WBRKeyword::Neuroendocrine
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