Medical literature about the role of Endoscopic ultrasound (EUS) in identifying thyroid lesions is limited. We present a case of secondary thyroid cancer from renal cell carcinoma (RCC) metastasis, diagnosed by thyroid EUS-fine needle aspiration (FNA) approach that was done for staging of esophageal adenocarcinoma, in a patient with 11 years history of complete right nephrectomy for RCC. An 81 year old female patient presented to our facility with dysphagea to both solids and liquids. Initial EGD examination of the esophagus revealed a distal esophageal mass of 5 cm in length, that was biopsied, and the histopathologic results revealed esophageal adenocarcinoma. For staging, the patient underwent computed tomography (CT) of the chest, which showed the lower esophageal mass with mediastinal lymphadenopathy. Next, the patient underwent upper gastrointestinal (GI) EUS for assessment of the esophageal adenocarcinoma and the mediastinal lymph nodes. The EUS-FNA examination of the mediastinal lymph nodes revealed no lymphatic spread. A diagnosis of esophageal adenocarcinoma with stage of T3N0M0 was made. Upon withdrawing the EUS scope, examination of the thyroid revealed a hypoechoic, round, and well-demarcated mass that measured 26.9 mm x 21.9 mm in the right lobe (Image1A). The radial echoendoscope was then withdrawn and the Olympus video curvilinear array echoendoscope was advanced through the mouth into the proximal esophagus. Under echoendosonographic guidance, FNA with a 25-gauge needle (Expect EUS-FNA 25 G needle; Boston Scientific, Menomonie, WI, USA) was performed successfully without adverse events (Image 1B). Cytopathologist was present in the room and confirmed the adequacy of the sample. The thyroid FNA results showed renal cell carcinoma with positive Immunohistochemical stains for PAX8 and CAIX while negative for thyroid transcription factor-1 (TTF1), thyroglobulin and chromogranin (Image 2A-C). A diagnosis of metastatic RCC was made. The patient had a history of right renal cell carcinoma (RCC) status post right nephrectomy 11 years ago (Image 2D). The patient was referred for further oncology work up and management. In conclusion, diagnosis of metastatic RCC to thyroid by EUS-FNA approach during local staging of esophageal malignancy is feasible and safe.Figure: (A) EUS examination of the thyroid revealed a hypoechoic, round, and well-demarcated mass that measured 26.9 mm x 21.9 mm in the right lobe. (B) Under EUS guidance, FNA with a 25-gauge needle (Expect EUS-FNA 25 G needle; Boston Scientific, Menomonie, WI, USA) was performed successfully.Figure: (A) Cell block of thyroid nodule FNA is displaying multiple nests of clear cells, which have clear to eosinophilic cytoplasm. These nests are separated by delicate vascular network and surrounded by lymphocytic infiltrate (H&E stain, original magnification X 400). (B) Staining of Cell block with PAX-8 shows strong nuclear positivity (PAX-8 immunohistochemistry stain, original magnification X 200). (C) Staining the cell block with thyroid transcription factor-1 (TTF-1) shows negative staining (TTF-1 immunohistochemistry stain, original magnification X 200). (D) Kidney section is showing multiple nests of clear cells, which have clear to eosinophilic cytoplasm. These nests are separated by delicate vascular network (H&E stain, original magnification X 400).
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