Background: Although the thyroid is a highly vascularizedgland, it is not a common target of metastasis fromextrathyroidal cancer. Clear-cell renal carcinoma (cRCC)frequently metastasizes to the thyroid, representing 2-3% ofall adult tumors, and more than 40% of patients present withmetastases at diagnosis. The presence of cRCC thyroidalmetastases makes the differential diagnosis from thyroid clearcellcarcinoma extremely difficult. Patients and Methods: A70-year-old woman presented with a mild compressivesymptomatology due to a recent multinodular thyroid goiterwith a ‘simple’ multinodular ultrasound pattern, in the absenceof signs of malignancy and with normal findings for hormonaland immunological assessment. Clinical history presentedchronic renal failure under hemodialytic treatment subsequentto a right nephrectomy carried out 2 years before for anunspecified cause. A volumetric increase of the whole glandwas evident, with absence of laterocervical adenopathy. A totalthyroidectomy was performed. Results: Histologicalexamination showed an enlargement of the thyroid with adistorted shape; the cross-section showed multiple nodules,some with firm appearance and others with colloidalappearance. The sections showed nodules with firmappearance surrounded by a complete fibrous capsule andcharacterized by proliferation of large cells, with abundantoptically clear cytoplasm and well-defined margins, arrangedin an alveolar-tubular pattern (nests and cords). The nucleiexhibited mild to moderate atypia and single or multiplenucleoli. Few mitoses were observed. Within the nodules,several dilated vascular structures were visible, some of whichshowing angiolymphatic invasion. The neoplastic cells werestrongly immunoreactive for CD10 (commonly expressed incRCC) and vimentin. By contrast, thyroid transcription factor-1 (TTF-1), thyroglobulin and CK7 were not found in tumoralcells and this ruled out a primary tumor of the thyroid. On thegrounds of the morphological and immunohistochemicalfindings, along with the patient’s medical history, a diagnosisof intrathyroid metastasis of cRCC was made. Contacting thepatient’s relatives for more information about his renal disease,they revealed that the nephrectomy had been due to cRCC,which had been concealed from the patient. This clarificationconfirmed the histological diagnosis of thyroid metastasis ofcRCC, on a background of micro- and macrofollicularcolloidal goiter. The patient underwent a whole-body CT scanand bone scintigraphy that was negative for metastases.Therefore, being at low-risk and under hemodialytic treatment,the patient was sent for oncologic follow-up. Discussion andConclusion: Many patients suffering from thyroid metastasespresent a local symptomatology which is not easy todistinguish from that caused by primary pathologies of thethyroid. In the case we described here, the difficulty ofdiagnosis was not only due to the rarity of this condition, butwas also complicated by the lack of information about thecause of the previous nephrectomy. In secondary thyroidlesions, it is necessary to ensure the total eradication of thegland (even for suspected malignant pathology) in order toguarantee oncologic radicality and extend the patient’ssurvival.
|Number of pages||2|
|Publication status||Published - 2011|