Medullary thyroid microcarcinoma

Abstract

BACKGROUND: Medullary thyroid microcarcinomas (microMTCs) are medullary thyroid carcinomas (MTCs) that measure 1 cm in size for which there is a paucity of data on incidence, characteristics, and clinical significance. METHODS: Patients who had a diagnosis of microMTC were abstracted from the Surveillance, Epidemiology, and End Results database (1988)(1989)(1990)(1991)(1992)(1993)(1994)(1995)(1996)(1997)(1998)(1999)(2000)(2001)(2002)(2003)(2004)(2005)(2006)(2007). The data were analyzed using chi-square tests, t tests, and log-rank tests; multivariate logistic regression was used to identify factors that were associated independently with lymph node metastases. Tests for diagnostic accuracy, including likelihood ratio tests and post-test probability tests, were computed to evaluate the size-specific likelihood of developing lymph node metastases among patients with microMTC. RESULTS: In total, 310 patients had microMTC; its incidence increased during the study period (P trend ¼ .033), and microMTC as a proportion of all MTCs increased by 39%. The mean tumor size was 5.7 mm. Thirty-one percent of tumors were multifocal, and 7.8% had extrathyroid extension. Lymph node metastases occurred in nearly 37% of patients who had any lymph nodes removed (65 of 176 patients). Nearly 20% of patients had regional disease, and 5% had distant metastases. The overall 10-year survival rates for patients with localized, regional, and distant disease stages were 96%, 87%, and 50%, respectively (P < .001). After adjustment, extrathyroid extension (odds ratio [OR], 41.9; P < .001) and tumor size (OR, 1.2; P ¼ .008) retained an independent association with lymph node metastases. MTCs that measured 5 mm were associated with a probability of lymph node metastases of approximately 23%, and the probability increased for patients who had tumors >5 mm. CONCLUSIONS: The current results indicated that microMTCs have significant rates of poor prognostic features known to impact the survival of patients with MTC. These microcarcinomas are an important clinical entity that requires comprehensive evaluation and surgical management. Cancer 2012;118:620-

Small medullary thyroid carcinoma: post-operative calcitonin rather than tumour size predicts disease persistence and progression

“…The variance in cure rates may be due to differences in the chronological periods and the ratio of familial disease. Death in microMTC patients has been reported in older studies where the 10-year survival was 96% for localised tumours and 87% for regional tumours (4,19,24). In microMTC patients with positive lymph nodes at diagnosis, undetectable post-operative calcitonin was found in 28.6% compared with 76.8% in those without positive lymph nodes at diagnosis, roughly agreeing with the findings of Scollo et al (15) (32 vs 95%).…”

“…Hamy et al only observed lymph node involvement; thus, older studies have questioned the extent of surgical treatment needed (7,11,12). However, two recent studies have reported that even small tumours may present with more advanced disease (4,13). Finally, in patients with a hereditary MTC, who frequently have small tumours due to earlier diagnosis, the clinical course and prognosis are better (13).…”

“…Thus, whether tumour size could predict the clinical behaviour of MTCs would be an important question. This would be of importance not only for the prognosis of the disease but also for the surgical procedure to be followed (4,7,13,15,16). Towards this direction, there have been many efforts to establish a cut-off value of tumour size that could distinguish those patients who are at a higher risk for progressive disease.…”

“Atypical” Non-Secretory Medullary Thyroid Carcinoma: Case Report and Review of the Literature

“…If we could divide these negative calcitonin MTC into two categories, one were cancer cells show diffuse staining for calcitonin and another with weak and focal immunoreactivity, we could say that in the first category MTC maintain its ability to produce calcitonin but lose its ability to secrete it, whereas in the second category cancer cells cannot produce calcitonin. In regards to the first type of negative calcitonin MTC, one could hypothesize that there might be a defect in the secretory mechanism, or that the tumor preferential secrete precursor peptides and aberrant forms of calcitonin instead of the mature molecule [6], or that a mutation in the calcitonin/CGRP gene is responsible for the normal or reduced serum calcitonin [4]. When it comes to the second category, we already know that in progressive disease calcitonin levels may decrease due to dedifferentiation [9,15], we could consider that tumor cells with weak calcitonin expression indicate a loss of function and there for dedifferentiation and more aggressive nature [7,14].…”

“…In fact it is the second most aggressive thyroid cancer after anaplastic carcinoma [4], with a mortality rate that ranges between 13, 4 -38% [2][3][4][5]. Its poor prognosis relies not only on its aggressive nature but also on its limited response to chemotherapy and radiation [6]. Currently the only possible mean of care for MTC is surgical excision [7].…”