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Sporadic minute medullary thyroid carcinoma with a double RET mutation: A case report
Author(s) -
Yamamoto Hiroyuki,
Ishii Jun,
Chiba Tomohiro,
Nakazato Yoko,
Hirano Kouichi,
Kamma Hiroshi
Publication year - 2017
Publication title -
pathology international
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.73
H-Index - 74
eISSN - 1440-1827
pISSN - 1320-5463
DOI - 10.1111/pin.12588
Subject(s) - pathology , thyroid , missense mutation , medicine , thyroid carcinoma , somatic cell , hyperplasia , mutation , goiter , germline mutation , cancer research , biology , gene , genetics
We describe a 74‐year‐old man with a nodular goiter accompanied by an incidental sporadic minute medullary thyroid carcinoma (MTC). Histopathologically, the MTC was a well‐defined 1.7 mm tumor in the upper one‐third right lobe, with solid cell nests (SCNs) adjacent to the MTC. C‐cells were scattered mainly around the SCNs, but C‐cell hyperplasia was not evident in the background thyroid. The MTC cell phenotype was immunohistochemically identical to background C‐cells, but was completely different from the SCN main cells. Direct DNA analyses of isolated MTC paraffin‐embedded specimens revealed two RET proto‐oncogene missense point mutations in exon 11 (i.e., C630R and C634W). The non‐tumor thyroid tissue did not reveal any mutations. This study reports the smallest case of sporadic MTC with a double RET somatic mutation, substantiating that RET mutations can occur during a very early stage of carcinogenesis. The combined presence of C630R and C634W represent a novel somatic mutation in sporadic MTC. The present case indicates that the sporadic MTC originated from the surrounding C‐cells of the SCNs without C‐cell hyperplasia and that the SCN main cells may not be able to develop into an MTC.