The survival of patients with MTC is intermediate to that of patients with differentiated thyroid cancer of follicular cell origin and anaplastic thyroid cancer, with an overall 10-year survival rate of 75 to 85%.1,2,10 There is great variability, however, in the clinical course of patients with MTC. Some patients may survive several decades with persistent disease, whereas some will have rapidly progressive tumors and will die within months of presentation. Only early diagnosis and at least a total thyroidectomy with central neck node clearance give the patient the best chance of disease-free survival. A number of clinical, biochemical, and molecular factors have been reported to predict outcome in patients with MTC (Table 3-2). The most important prognostic factors consistently observed are the age of the patient and the stage of MTC.10 Some studies, but not all, have also suggested that male gender is associated with a worse prognosis. The presence of diarrhea, cervical node metastasis, large tumor size, extrathyroidal tumor extension, and elevated stimulated serum calcitonin levels (> 10,000 pg/mL) at the time of diagnosis have also been shown to adversely influence survival.33 Deoxyribonucleic acid (DNA) ploidy (aneuploid tumors), increased N-myc immunoreactivity (messenger ribonucleic acid), weak calcitonin immunostaining (suggesting tumor dedifferentiation), absent amyloid staining, elevated serum CEA levels, absent somatostatin receptor tumor staining, and the absence of thyroiditis have also been implicated as markers of poor prognosis.33
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