Thyroid cancer in children: report of three cases and a review of the Japanese literature

Childhood minimally invasive follicular carcinoma: clinical features and immunohistochemistry analysis

AIM

To report on two cases of childhood thyroid minimally invasive follicular carcinoma (MIFC) to highlight the clinical features, laboratory findings and diagnosis of this rare disease.

METHODS

The patients' age, gender, clinical features, laboratory findings, pathology and therapy were reviewed. Immunohistochemistry analysis was performed on the resected masses section.

RESULTS

From 2000 to 2008, a total of 15 cases of thyroid cancer were confirmed by pathological analysis, which account for about 2.16% of all malignant solid tumours. They included nine of thyroid papillary carcinoma, two of MIFC and one of undifferentiated thyroid carcinoma. For the two children with MIFC, one was an 8-year-boy and one was a 12-year-old girl. Thyroid mass was found as the primary sign. Imaging findings showed well-defined heterogeneous mass and radionuclide scintigraphy with 99mTc demonstrated small cold nodules in the right lobe of thyroid in two cases. Histopathology confirmed the diagnosis of MIFC. Immunohistochemical staining was positive for thyroglobulin, thyroid transcription factor-1, galectin-3, Hector Battifora mesothelial antigen-1, cytokeratin-AE1/AE3, cytokeratin-19, proliferating cell nuclear antigen and E-cadherin in two cases, and S-100 in one case, while CD56, vimentin and desmin were negative. One case was undertaken lobectomy and the other was undertaken subtotal thyreoidectomy with L-T4 replacement therapy.

CONCLUSION

MIFC is exceedingly rare in children and should be included in the differential diagnosis of thyroid mass. The diagnosis of MIFC depends mainly on the pathological findings.

Low frequency of BRAFT1796A mutations in childhood thyroid carcinomas

A high prevalence of the activating BRAF mutation, BRAF(T1796A), is observed in adult papillary thyroid carcinomas (PTCs). The prognosis of childhood PTCs is generally fairly good despite the fact that distant metastases are often documented in these cases. To investigate the differences between the characteristics of childhood and adult PTCs, we analyzed both BRAF(T1796A) and RAS mutations in 31 Japanese and 48 post-Chernobyl Ukrainian thyroid carcinomas. In the 31 Japanese childhood cases, BRAF(T1796A) was found in only one instance (3.2%), and no RAS mutations were detected. In the Ukrainian subjects, of the 15 childhood and the 33 adolescent and young adult PTCs examined, the BRAF(T1796A) mutation was found in zero and eight cases, respectively, and RAS mutations were found in two of the young adult cases. In addition, 17 of the 48 Ukrainian cases showed expression of the RET tyrosine kinase region, indicating the existence of RET/PTC rearrangements. Unlike adult PTCs, we could detect no positive association between BRAF(T1796A) mutations and clinical parameters in the childhood carcinomas, suggesting that a low prevalence of BRAF(T1796A) is a common feature of PTCs in children regardless of radiation exposure levels. The differences in the prevalence of BRAF(T1796A) mutations between childhood and adult cases of PTC may well reflect inherent differences in the clinical features of these cancers between the two age groups.