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Medical AI Inquiry: You was designed to assist in medical decision-making based on the provided user questions. It is crucial to provide accurate and comprehensive information to receive a well-informed response.  Labels: OBJECTIVE, METHODS, RESULTS. Meshes: Aromatic-L-Amino-Acid Decarboxylases, Dopamine, Dopamine beta-Hydroxylase, Female, Head and Neck Neoplasms, Humans, Immunohistochemistry, Male, Metanephrine, Middle Aged, Normetanephrine, Pheochromocytoma, Tyrosine 3-Monooxygenase.
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Do catecholamine-Synthesizing Enzymes Are Expressed in Parasympathetic Head and Neck Paraganglioma Tissue? Context: Increased dopamine production may be a feature of head and neck paraganglioma (HNPGL). 18F-fluorodihydroxyphenylalanine positron emission tomography scintigraphy has a high sensitivity for detecting HNPGLs. These observations strongly suggest that HNPGLs have the capacity for L-3,4-dihydroxyphenylalanine uptake and conversion towards dopamine. Therefore, our aim was to demonstrate the presence of catecholamine-synthesizing enzymes, i.e. tyrosine hydroxylase (TH), aromatic L-amino acid decarboxylase (AADC) and dopamine β-hydroxylase (DBH) in HNPGL tissue. A single-center study was performed among patients who underwent surgery for HNPGL at a single university referral center between 1994 and 2012. HNPGL tissue was immunohistochemically stained for TH, AADC and DBH. Data on paraganglioma-associated germline mutations, preoperative biochemical phenotype and imaging studies were retrieved. Catecholamine excess was defined as preoperative plasma and/or urinary levels of metanephrine, normetanephrine or 3-methoxytyramine above the upper reference limit. Nineteen HNPGLs from 18 patients were evaluated. All tumor tissues (100%) stained positive for AADC, 6 (32%) for TH and 2 (11%) for DBH. Of 3 HNPGLs staining positive for DBH, 2 were also positive for AADC and TH. Catecholamine excess was only present in 1 patient (5%). The HNPGLs of this single patient only showed positive staining for AADC.
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Catecholamine-synthesizing enzymes, in particular AADC, are expressed in the majority of HNPGL tissues. Final Decision: yes