Romei C, Ugolini C, Cosci B, Torregrossa L, Vivaldi A, Ciampi R, Tacito A, Basolo F, Materazzi G, Miccoli P, Vitti P, Pinchera A, Elisei R. Low prevalence of the somatic M918T RET mutation in micro-medullary thyroid cancer.
Thyroid 2012;
22:476-81. [PMID:
22404432 DOI:
10.1089/thy.2011.0358]
[Citation(s) in RCA: 45] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
BACKGROUND
The prevalence of RET somatic mutations in sporadic medullary thyroid cancer (MTCs) is ∼40%-50%, and the most frequent somatic mutation is M918T. RET-positive MTCs have been demonstrated to have a more advanced stage at diagnosis and a worse outcome.
AIMS
The aim of the present work was to compare the prevalence of RET somatic mutations in sporadic microMTCs (<1 cm) and in larger MTCs.
PATIENTS
We analyzed the M918T RET point mutation in 160 sporadic MTC cases. Tumors were classified according to their size: group A, <1 cm; group B, >1 and <2 cm; group C, >2 and <3 cm; and group D, >3 cm.
RESULTS
The overall prevalence of the somatic M918T RET mutation was 19.4% (31/160). RET mutations were distributed differently among the four groups. The prevalence was 11.3% (6/53) in group A, 11.8% (8/68) in group B, 31.8% (7/22) in group C, and 58.8% (10/17) in group D, exhibiting an increase with increasing size of the tumor. When comparing the prevalence of mutations in the four groups, we found a lower prevalence in microMTCs (p<0.0001).
CONCLUSIONS
The overall prevalence of RET somatic mutations was lower than expected, and the prevalence of the somatic M918T RET mutation was significantly lower in microMTCs than in larger tumors. To explain this finding, we can hypothesize either that other oncogene(s) might be responsible for the majority of microMTC, thus identifying a tumor subset, or that the RET mutation might, or might not, occur later during tumor progression.
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