RESUMEN
BACKGROUND: A secondary lesion in the thyroid gland is a rare clinical scenario diagnosed preoperatively during the evaluation of a neck mass, postoperatively in a thyroidectomy specimen or in autopsy studies. Even though the thyroid gland is highly vascular, secondary malignant lesions are rare accounting for 0.2% of all thyroid malignancies. Thyroid gland secondary lesions are often metachronous in presentation as they are seldom evaluated in the initial diagnostic workup of the primary lesion. Fine-needle aspiration cytology (FNAC) is a useful modality for the diagnosis of secondary thyroid lesions. MATERIALS AND METHODS: A 6-year retrospective review (2016-2021) was carried out to assess the secondary lesions in the thyroid gland. Papanicolaou and field-stained FNAC smears of secondary thyroid lesions were reviewed. Ancillary techniques were performed on the cell block for differentiating from the primary thyroid gland lesions. RESULTS: There were 383 patients in our archives. There were only 18 cases (4.7%) that presented with secondary neoplastic lesions in the thyroid gland either by direct extension, metastases or as a hematolymphoid malignancy. There were 14 (77.7%) cases that presented with non-hematolymphoid secondary lesions while 4 (22.3%) cases presented with hematolymphoid malignancies. Thyroid secondaries were predominantly seen in female patients (female: male ratio of 1.5:1). Most of the cases presented with a synchronous secondary lesion (n = 14, 77.7%) and few metachronous secondary lesions were also noted (n = 4, 22.3%). CONCLUSION: Although exceedingly rare, the detection of secondary thyroid gland lesions is important for staging and planning treatment.