Follicular Thyroid Carcinoma Masquerading as Subacute Thyroiditis Diagnosis using Ultrasonography and Radionuclide Thyroid Angiography

Abstract

The rare presentation of a follicular thyroid carcinoma mimicking the clinical and radionuclide features of subacute thyroiditis is described. Granulomatous thyroiditis was initially suspected on the clinical basis of acute onset of a hard, tender right lobe thyroid enlargement with associated systemic symptoms, modest elevation of thyroid hormone levels and suppressed thyroid RAIU. Fine needle aspiration cytology specimens were unsatisfactory for characterization. Three weeks later the thyroid RAIU was normal. The thyroid enlargement persisted, now being clearly visualized as a hypofunctional nodule on scintiscan. Repeat fine needle aspiration cytology was suggestive of acinar proliferation with hyperfunction. Ultrasonography revealed a solid nodule with a peripheral sonolucent halo. Radionuclide angiography showed intense arterial flow of Tc-99m pertechnetate through the right lobe thyroid enlargement suggestive of malignant thyroid pathology. Surgical excision and histopathological examination revealed a follicular carcinoma involving the right lobe. The possibility of carcinomatous involvement should be considered in those patients where initially tender thyroid nodularity persists longer than expected for a benign inflammatory disease, careful follow-up and relevant investigations being necessary to confirm the diagnosis.

Thyroid primary and metastatic malignant tumours of poor prognosis may mimic subacute thyroiditis - time to change the diagnostic criteria: case reports and a review of the literature

“…Differentiated thyroid cancers progress much slower than anaplastic cancers, rarely give extensive infiltration of neck tissues and usually are not associated with significant ESR. However, Prakash et al [8] described a case of follicular thyroid cancer that manifested as hard, tender right thyroid lobe enlargement, associated with modest elevation of thyroid hormone levels and suppressed thyroid RAIU. Unfortunately, no ESR result of this patient is available in that paper.…”

The co-occurrence of SAT, hypophysitis, and Schnitzler syndrome after COVID-19 vaccination: the first described case

“…In the differential diagnosis of SAT, other causes of painful goiter should be considered, including rapidly growing thyroid cancers, lymphomas (including Hodgkin lymphoma) [65], metastases [66], hematomas, or Pneumocystis carini infection. Highly aggressive tumors (such as anaplastic carcinoma) rapidly infiltrate the surrounding tissues, including the neck muscles, and may cause symptoms similar to those of SAT.…”

“…Thyroid abscess may also be difficult to differentiate from SAT and sometimes may develop as a result of infection of necrotic tissues in anaplastic carcinoma, as described by Lewiński et al [6]. Prakash et al reported a case of follicular cancer with clinical presentation that mimicked SAT as it manifested with hard and painful right lobe of the thyroid [66]. It must be kept in mind that good therapeutic response to glucocorticoids is not a diagnostic criterium for SAT since improvement with steroid therapy can also be seen in some cancers, metastatic lesions, and amyloidosis [67].…”

Diagnostic cytological features and differential diagnosis of subacute granulomatous (De Quervain's) thyroiditis

“…Certain USG and cytological features of SGT are reported to mimic thyroid carcinomas in the literature, leading to unnecessary surgical resections . The reactive cytological features of SGT that cause false positivity should be known to prevent unnecessary surgical resections.…”