engleski

Intrathyroid metastasis of malignant melanoma: a case report

Aim: Metastases to the thyroid gland are rare, especially in the case of intrathyroid metastasis of malignant melanoma. The aim of our case report is to present results of incidentally found focal pathological intrathyroid FDG-uptake detected in patient with malignant melanoma who underwent staging using FDG-PET/CT scanning. Materials and methods: A 67-year-old female patient underwent staging of malignant melanoma of the skin on the right shoulder using F18-FDG-PET/CT scanning. Pathological FDG-uptake was detected in thyroid nodule (19 x14 mm) in the lower left thyroid lobe that required further investigation. Another hypodense lesion of 9 mm in diameter was detected in the right lower lobe, but without pathological FDG accumulation. The patient underwent further examination including determination of thyroid hormones, thyroid ultrasonography (US), thyroid scintigraphy using 99mTc-pertehnetate, and fine-needle aspiration cytology (FNAC). Results: The patient showed no clinical or hormonal signs of thyroid dysfunction. US of the thyroid confirmed nodules that were already detected on PET-CT and showed additional two nodules. Thyroid scintigraphy registered an inhomogeneous accumulation of radiopharmaceutical in the right lower lobe and a "hot" nodule in the left lower lobe. An US guided FNAC of the nodule in the left lower lobe showed follicular changes of thyroid cells (differential diagnosis of adenomatoid nodule and follicular tumor). An additional FNAC, from the right lower lobe, detected cellular changes typical for metastatic melanoma. Based on these findings, the patient was referred for total thyroidectomy. Postsurgical pathological diagnosis confirmed diagnosis of metastatic melanoma in the nodule in right lower lobe, but also revealed foci of metastatic melanoma within the adenomatoid nodule in the left lower lobe that was not found on FNAC. Conclusion: An intrathyroid metastasis from malignant melanoma was determined in the FDG positive and scintigraphic "hot" nodule in the left thyroid lobe, but also in the other nodule without increased FDG uptake. False-negative FDG-PET result of the intrathyroid metastatic melanoma could be explained by limitations of this method to detect micrometastases and lesions smaller than 1 cm. Presented case suggests that all intrathyroid nodules detected by F18-FDG-PET/CT, not only those with pathological FDG uptake, should undergo further investigation.

Thyroid; Metastasis; Melanoma

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