Surgery for metastatic tumors of the pancreas

The pancreas is an unusual but occasionally favored site for metastasis, notably from carcinoma of the kidney and lung [1–3, 15]. In this series of the patients, 77.8% (case nos. 1–7) pancreatic tumor were metastasis from clear cell RCC and 11.1% (case no. 7) were from rectal cancer, consistent with previous studies [4–7]. Interestingly, all metastatic tumors from the left RCC (3 cases) were developed in the left side of the pancreas. This tendency of metastatic direction to the pancreas has been never reported and may indicate the mechanism of hematogenous metastasis from the kidney to pancreas. In patients with portal hypertension, vascular endothelial growth factor (VEGF)-dependent angiogenesis plays a crucial role in the formation of portal-systemic collateral vessels, which include spleno-renal shunts [16]. VEGF has an important role in progression of RCC [17]. Collateral vessels like spleno-renal shunts dependent on VEGF angiogenesis possibly contribute to the tendency of metastatic direction in RCC patients. One case of our series was the metastasis from oral malignant melanoma, with poor prognosis even the aggressive chemotherapy by dacarbazine. There were a few reports indicated similar situation [18, 19]; however, it appears that surgical resection is only a palliative procedure, because long-term survival is a rare event.

Despite the technological advances, preoperative diagnosis of the metastatic pancreatic tumor is sometimes difficult [15]. EUS-FNA is an excellent method for procurement of diagnostic samples from the pancreas, with a diagnostic accuracy of more than 90% for pancreatic adenocarcinoma [20, 21]. One patient in this study (case no. 6) was preoperatively diagnosed as metastasis of clear cell RCC by EUS-FNA, even only 10 mm of the size of the tumor. It suggested that EUS-FNA is useful to correct diagnosis of metastatic pancreatic tumor.

Surgical resection of the metastatic tumor to the pancreas should be approached by carefully applying appropriate selection criteria, because of the substantial morbidity indicated in this series and a previous report [22]. On the other hand, a noteworthy finding in our series was a long interval from the initial surgery to the pancreatic metastasis and long survival after pancreatic resection. This was particularly the cases with clear cell RCC patients. Yuasa et al. reported that the median duration from diagnosis of RCC to pancreatic metastasis was 7.8 years (4.2–12.7 years) [23]. Consistent with the study, metastatic tumor of the pancreas from RCC is recurred in long-term interval in general in our series. Patients with isolated RCC metastasis to the pancreas, whether synchronous or metachronous, represent a selected group of patients with more indolent RCC [22]. In addition, new effective therapeutic strategy such as molecular target drug has been introduced to metastatic disease from clear cell RCC [24]. This advantage may provide the benefit of resection of the pancreatic metastasis even with metastatic lesions in other organs such as the lung, in selected cases with good response to the treatment, as indicated in our study.

We performed distal pancreatectomy in 6 cases, pancreaticoduodenectomy in 2 cases, and total pancreatectomy in 1 case. The surgical strategy for pancreatic metastatic tumor has not been established. Recently, limited or partial pancreatectomy has been performed, especially for disease which does not need lymph node dissection [25]. These preserving operations may be useful for patients with pancreatic metastasis from clear cell renal cell carcinoma.

In conclusion, the metastasis to the pancreas can be developed years after the initial surgery of the primary disease. EUS-FNA was suggested to be feasible for diagnosis and helpful to consider the indication of surgery. Long-term survival can be archived with pancreatic resection, especially in patients with pancreatic metastasis from clear cell RCC.