Primary Extrarenal Renal Cell Carcinoma: A Unique Diagnosis Performed through Endoscopic Ultrasound

Renal cell carcinoma (RCC) is the most common kidney cancer in adults, accounting for more than 90% of renal neoplasms. Clear cell carcinoma is the most prevalent histologic subtype followed by papillary RCC. They are thought to be derived from nephron proximal tubules [1]. Endoscopic ultrasound with fine-needle aspiration (EUS-FNA) plays a major role in the diagnosis and staging of gastrointestinal malignancies. It also proved to be effective in assessing and sampling both adrenal glands [2]. A 62-year-old asymptomatic male underwent a routine abdominal ultrasound which was unremarkable except for a 9-cm right adrenal mass. No additional lesions were seen on computed tomography (CT) and a laparoscopic right adrenalectomy was performed. Surgical pathology revealed a well-delimited tumour with bleeding and necrotic areas. It was composed by papilla coated by cells with nuclear pseudostratification, rounded nucleus with irregular nuclear membrane, prominent nucleolus, and eosinophilic cytoplasm. Surgical margins were tumour free and the remaining adrenal parenchyma was normal. Immunohistochemistry (IHC) was positive for RCC Ma, CK7, CD10, and racemase, being negative for CK20, CD117, and all adrenal cortex markers (MelanA, calretinin, inhibin, synaptophysin, and chromogranin A). Although these findings were suggestive of metastatic papillary RCC, both kidneys were normal in the abdominal MRI. Of note, whole body positron emission tomography (PET-CT) was negative. One year later, a new left adrenal nodule was detected on a surveillance CT. The patient was referred for EUS, which revealed a well-delimited isoechoic nodule with a diameter of 24 mm and a 3-mm cystic area inside. The lesion was punctured with a 22-gauge needle (Fig. 1). Cell