A Rare Case of Heterozygous Gain of Function Thyrotropin Receptor Mutation Associated with Development of Thyroid Follicular Carcinoma

Locally invasive classical papillary thyroid carcinoma with TSH receptor I568T mutation: case report

Summary

Autonomous thyroid adenomas are caused by activating mutations in the genes encoding the thyroid-stimulating hormone receptor (TSHR) or mutations in the Gas subunit of the TSHR. Nodules with suspicious sonographic features should be submitted to fine-needle aspiration. Additional molecular testing may be performed to characterize the thyroid nodule's malignant potential further. We present a patient who underwent whole-transcriptome RNA-sequencing that indicated a TSHR I568T mutation after an ultrasound showed suspicious sonographic features and fine-needle aspiration was 'suspicious for malignancy'. The patient underwent thyroid resection and was found to have a locally invasive classical papillary thyroid carcinoma. Most reports of TSHR I568T mutation have been seen in patients with benign thyroid conditions. While there is insufficient data to suggest that the TSHR I568T mutation causes aggressive thyroid malignancy, we believe clinicians who identify the presence of this mutation on genome sequencing should be cautious about the possibility of locally invasive thyroid malignancy, especially when associated with Bethesda V cytopathology.

Learning points

Germline and somatic activating mutations in the genes coding for the thyroid-stimulating hormone receptor (TSHR) have been frequently reported in familial and sporadic autonomous thyroid adenomas and non-autoimmune hyperthyroidism. Most reports of TSHR I568T mutation have been detected in patients with benign thyroid conditions. We present a patient who underwent whole-transcriptome RNA-sequencing that indicated a TSHR I568T mutation and subsequently underwent thyroid resection and was found to have a locally invasive classical papillary thyroid carcinoma. Clinicians who identify the presence of TSHR I568T mutation on genome sequencing should be cautious about the possibility of locally invasive thyroid malignancy, especially when associated with Bethesda V cytopathology.

A synchronous papillary and follicular thyroid carcinoma presenting as a large toxic nodule in a female adolescent

Case presentation

We report for the first time a synchronous papillary and follicular thyroid carcinoma in a 12-year-old girl presenting with a large (5 cm diameter) left thyroid nodule, an increased left and right upper pole technetium tracer uptake at scintigraphy and hyperthyroidism. The uptake at the right lobe was explained by the crossing of the left nodule to the right site of the neck at Computed Tomography (CT) scanning.

Background

Although thyroid nodules are less common in children than in adults, there is more vigilance required in children because of the higher risk of malignancy. According to literature, about 5% of the thyroid nodules in adults are malignant versus 20–26% in children. The characteristics of 9 other pediatric cases with a differentiated thyroid carcinoma presenting with a toxic nodule, which have been reported during the last 20 years, are summarized. A nodular size of more than 3.5 cm and female predominance was a common finding.

Conclusions

The presence of hyperthyroidism in association with a hyperfunctioning thyroid nodule does not rule out thyroid cancer and warrants careful evaluation, even in the absence of cervical lymph node invasion.

The Thyrotropin Receptor Mutation Database Update

The thyrotropin receptor (TSHR) mutation database, consisting of all known TSHR mutations and their clinical characterizations, was established in 1999. The database contents are updated here with the same website (tsh-receptor-mutation-database.org). The new database contains 638 cases of TSHR mutations: 448 cases of gain of function mutations (7 novel mutations and 41 new cases for previously described mutations since its last update in 2012) and 190 cases of loss of function mutations (28 novel mutations and 31 new cases for previously described mutations since its last update in 2012). This database is continuously updated and allows for rapid validation of patient TSHR mutations causing hyper- or hypothyroidism or insensitivity to TSH.