Differentiation between pancreatic metastases from renal cell carcinoma and pancreatic neuroendocrine neoplasm using endoscopic ultrasound

Objectives: Pancreatic metastases from renal cell carcinoma (PRCC) often appear many years after treatment of the primary tumor, and differentiation from pancreatic neuroendocrine neoplasm (PanNEN) can be challenging due to their hypervascularity. Here, we investigated the utility of endoscopic ultrasound (EUS) for differentiation of these conditions. Methods: A retrospective analysis was performed in 17 and 79 consecutive patients with pathologically proven PRCC and non-functional PanNEN who were examined by EUS. In cases examined by EUS elastography or contrast-enhanced harmonic EUS (CH-EUS), the lesions were classified as stiff or soft, or into three vascular patterns as hypoechoic, isoechoic, and hyperechoic. CH-EUS images at 20 s, 40 s, 60 s, 3 min and 5 min were used for evaluation. EUS images were independently reviewed by two readers who were blinded to all clinical information. Results: The patients with PRCC were significantly older than those with PanNEN (median, 71 (range, 45–81) vs. 58 (22–76), P = 0.001) and more often had multiple tumors (6/17 (35%) vs. 7/79 (9%), P = 0.010). In EUS findings, PRCC lesions significantly more frequently had a marginal hypoechoic zone (MHZ) (11/17 (65%) vs. 27/79 (34%), P = 0.028), being classified as soft (12/13 (92%) vs. 26/58 (45%), P = 0.002), and showed sustained hyperechoic vascular patterns at 5 min (7/8 (88%) vs. 4/59 (7%), P < 0.001) compared to PanNEN lesions. Conclusions: The presence of a MHZ, a soft lesion, and a sustained hyperechoic vascular pattern in EUS may be useful for differentiating PRCC from PanNEN.