Thyroid tumour in a child previously treated for neuroblastoma

The Current Histologic Classification of Thyroid Cancer

Thyroid cancers of follicular cell derivation provide excellent phenotype-genotype correlations. Current morphologic classifications are complex and require simplification. Benign adenomas have follicular or papillary architecture and bland cytology. Well-differentiated thyroid carcinomas exhibit follicular architecture, expansile growth, and variable cytologic atypia and invasiveness; low-risk tumors have excellent prognosis after surgical resection whereas widely-invasive and angioinvasive tumors warrant total thyroidectomy and radioablation. Papillary carcinoma is less differentiated; indolent microcarcinomas can be managed by active surveillance, whereas clinical lesions with local or distant spread require therapy. Progression gives rise to poorly differentiated and anaplastic carcinomas that are less common but far more aggressive.

Differentiated thyroid carcinoma after 131I-MIBG treatment for neuroblastoma during childhood: description of the first two cases

BACKGROUND

It is well known that the thyroid gland is sensitive to the damaging effects of irradiation (X-radiation or (131)I¯). For this reason, during exposure to (131)I- metaiodobenzylguanidine (MIBG) in children with neuroblastoma (NBL), the thyroid gland is protected against radiation damage by the administration of either potassium iodide (KI) or a combination of KI, thyroxine, and methimazole. Although hypothyroidism and benign thyroid nodules are frequently encountered during follow-up of these children, differentiated thyroid carcinoma (DTC) has never been reported after treatment with (131)I-MIBG in children who have not been given external beam irradiation. Here, we describe the first two cases of DTC after (131)I-MIBG-therapy.

PATIENT FINDINGS

A 6-year-old boy, treated with (131)I-MIBG for NBL at the age of 4 months, and a 13-year-old girl, treated at the age of 9 months, were both diagnosed with DTC at 5 and 12 years after (131)I-MIBG treatment, respectively. Both children received thyroid protection during exposure to (131)I-MIBG. In each child DTC was discovered in nonpalpable nodules by thyroid ultrasound.

SUMMARY

The first two pediatric patients with DTC after treatment with (131)I-MIBG are reported.

CONCLUSIONS

Both these cases of DTC after (131)I-MIBG for childhood NBL underline the importance of adequate thyroid protection against radiation exposure during treatment for NBL. Children who have been treated with (131)I-MIBG should be given life-long follow-up, not only with regard to thyroid function, but also with surveillance for the development of thyroid nodules and thyroid cancer.