Follicular Variant of Papillary Thyroid Carcinoma Presenting as a Toxic Nodule by I-123 Scintigraphy

Abstract

The risk of malignancy in a "hot" thyroid nodule detected by radioiodine scintigraphy is rare. We report a case of a 63-year-old man with a hyperfunctioning nodule demonstrated by radioiodine scintigraphy and cytology suspicious for follicular variant of papillary thyroid carcinoma (FVPTC). There were no locoregional or distant metastases at initial diagnosis. Histopathologic examination following thyroidectomy confirmed the presence of an encapsulated FVPTC. A year into follow-up, his I-131 whole body scan performed following the withdrawal from exogenous thyroid hormone was negative, whereas his serum thyroglobulin (Tg) levels were intermediate. A subsequent PET/CT scan revealed a small, but stable, metabolically active pretracheal lymph node, which on biopsy was confirmed to be stage III FVPTC. In conclusion, the presence of hyperfunctioning thyroid nodule(s) does not preclude malignancy and, therefore, proper cytohistologic evaluation in such patients may help to exclude a coexistent thyroid carcinoma. Patients treated for localized PTC may benefit from serial PET/CT follow-up in the early detection and management of recurrence or distant metastases.

Follicular variant of papillary thyroid carcinoma: an unusual cause of thyrotoxicosis

“…Furthermore, all of the seven were papillary thyroid carcinoma, with one of these having the follicular variant subtype 2. We found only two case reports of hyperfunctioning follicular variant papillary thyroid carcinoma 4 5…”

Thyroid Carcinoma in Hot Nodules: Review of the Literature

“…Out of these 31 articles, 16 articles (five series of cases and 11 case reports) included cases matching the previously mentioned criteria for a total of 45 reported cases. 6,7,[11][12][13][14][15][16][17][18][19][20][21][22][23][24] Among these 45 cases, the histological repartition was as follow: 25 (56%) follicular carcinoma, 16 (36%) papillary carcinoma including at least four (9%) confirmed follicular variant, two (4%) Hürthle cells thyroid cancer, one (2%) poorly differentiated thyroid cancer and we were not able to find the histology for one case (Table 1).…”

Thyrotoxicosis with concomitant thyroid cancer

“…Except for etiologies mentioned above, thyrotoxicosis induced by ATC, HCC and FVPTC have also been described (Kumar et al 2005, Bommireddipalli et al 2010, Ruggeri et al 2013, Rees et al 2015, Daroszewski et al 2018. Additionally, painless thyroiditis-induced thyrotoxicosis has been reported to be associated with PTC (Valentini et al 2016).…”

“…For the mechanism of thyrotoxicosis with concurrent FVPTC, activation of the cAMP signal transduction system followed by the mutation of the TR gene, which is now thought to cause thyrotoxicosis, has been demonstrated in a great number of autonomously hyperfunctioning thyroid nodules (Bommireddipalli et al 2010).…”

“…Patients with thyrotoxicosis induced by FVPTC can be treated with ATDs to attenuate symptoms and signs of thyrotoxicosis. In general, patients with FVPTC-induced thyrotoxicosis undergo near/total thyroidectomy; and 131 I is subsequently administered not only for postsurgical thyroid remnant ablation and/or metastases therapy but for convenient periodical surveillance as well (Bommireddipalli et al 2010, Rees et al 2015.…”