Abstract
Recent studies have shown a significant increase in the temporal trend of medullary thyroid carcinoma (MTC) incidence. However, it remains unknown to which extent sporadic medullary thyroid carcinoma (SMTC) and hereditary MTC (HMTC) affect the MTC incidence over time. We conducted a nationwide retrospective study using previously described RET and MTC cohorts combined with review of medical records, pedigree comparison and relevant nationwide registries. The study included 474 MTC patients diagnosed in Denmark between 1960 and 2014. In the nationwide period from 1997 to 2014, we recorded a mean age-standardized incidence of all MTC, SMTC and HMTC of 0.19, 0.13 and 0.06 per 100,000 per year, respectively. The average annual percentage change in incidence for all MTC, SMTC and HMTC were 1.0 (P = 0.542), 2.8 (P = 0.125) and −3.1 (P = 0.324), respectively. The corresponding figures for point prevalence at January 1, 2015 were 3.8, 2.5 and 1.3 per 100,000, respectively. The average annual percentage change in prevalence from 1998 to 2015 for all MTC, SMTC and HMTC was 2.8 (P < 0.001), 3.8 (P < 0.001) and 1.5 (P = 0.010), respectively. We found no significant change in the incidence of all MTC, SMTC and HMTC possibly due to our small sample size. However, due to an increasing trend in the incidence of all MTC and opposing trends of SMTC (increasing) and HMTC (decreasing) incidence, it seems plausible that an increase for all MTC seen by others may be driven by the SMTC group rather than the HMTC group.
Highlights
Medullary thyroid carcinoma (MTC) is a neuroendocrine tumor arising from the calcitonin secreting parafollicular C cells of the thyroid gland
Relatedness to a nationwide cohort of REarranged during Transfection (RET) positive MEN2 families was assessed through pedigree comparison. This was performed to improve classification, as RET germline mutations have been reported in 1.5–14.9% of patients, who have been classified as apparently sporadic MTC (SMTC) in absence of MEN2 family history or other MEN2 features [16, 17, 18, 19, 20, 21, 22]
The mean age at diagnosis for all MTC patients was 52.4 years, while a significant difference was identified between the SMTC and hereditary MTC (HMTC) group (P < 0.001)
Summary
Medullary thyroid carcinoma (MTC) is a neuroendocrine tumor arising from the calcitonin secreting parafollicular C cells of the thyroid gland. MEN2A associates MTC, pheochromocytoma (PHEO), hyperparathyroidism (HPTH), cutaneous lichen amyloidosis and Hirschsprung’s disease, while MEN2B associates MTC, PHEO, ganglioneuromatosis of the aerodigestive tract, and facial, ophthalmologic and skeletal abnormalities. Both syndromes are caused by germline mutations of the REarranged during Transfection (RET) proto-oncogene [1, 2]. It remains unknown to which extent SMTC and HMTC affect the MTC incidence over time. We conducted the first nationwide study aiming to assess the significance of SMTC and HMTC in regards to the time trends in MTC incidence.
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