Synchronous Isolated Cystic Pancreatic Metastasis Arising From Primary Colorectal Cancer: A Rare Case Report

Introduction

Pancreatic cancer remains a major oncologic challenge due to its late presentation, aggressive course, and poor 5-year survival [1]. Whereas most pancreatic tumors are primary adenocarcinomas, metastatic lesions represent only 2% to 5% of pancreatic malignancies, and renal cell carcinoma is the most common primary source [2]. Colorectal pancreatic metastasis (CRPM) is exceedingly rare, particularly in the synchronous setting.

This rarity presents substantial diagnostic and therapeutic challenges. The pancreas is an unusual site for colorectal metastasis, and radiologic differentiation from primary pancreatic tumors – particularly cystic lesions – is difficult. Published case reports often describe metachronous disease, prolonged latency between primary tumor resection and pancreatic involvement, and heterogeneous treatment strategies. Due to limited data, management decisions are frequently extrapolated from renal cell carcinoma experience rather than colorectal-specific evidence.

The present case highlights these diagnostic difficulties and the complexity of treatment planning. By documenting a synchronous cystic pancreatic metastasis from colorectal cancer, this report adds to the small but growing body of literature and underscores the need for multidisciplinary evaluation and individualized treatment strategies.

Case Report

A 70-year-old man with diabetes and hypertension exhibited rectal bleeding, severe constipation, poor stool control, and fecal seepage. Physical examination and colonoscopy revealed a mass in the anterior lower rectum, whereas cross-sectional imaging identified a cystic lesion in the pancreatic uncinate process.

Tumor marker assessment showed a carbohydrate antigen 19-9 level of 93.4 U/mL and a carcinoembryonic antigen level of 3.4 ng/mL. Magnetic resonance imaging demonstrated a 5-cm cystic mass suggestive of an intraductal papillary mucinous neoplasm (Figure 1). Differential diagnoses included intraductal papillary mucinous neoplasm, mucinous cystic neoplasm, serous cystadenoma, pancreatic neuroendocrine tumor with cystic change, primary pancreatic adenocarcinoma, and metastatic disease.

Endoscopic-ultrasound-guided fine-needle aspiration confirmed adenocarcinoma consistent with colorectal origin. The case was reviewed at a multidisciplinary team meeting, and neoadjuvant therapy was initiated, consisting of 1 month of capecitabine-based chemoradiation followed by 4 cycles of FOLFOX (folinic acid, fluorouracil, and oxaliplatin). Post-treatment magnetic resonance imaging showed regression of the rectal tumor, and positron emission tomography-computed tomography demonstrated stable disease in the pancreatic lesion (Figure 2).

The patient underwent abdominoperineal resection. Pathological analysis demonstrated a post-treatment stage of pT2 pN0 cM1 with negative margins, according to the American Joint Committee on Cancer 8th edition pTNM classification. Pancreatic resection was planned 2 months later; however, the procedure was aborted due to mesenteric root involvement.

Four additional cycles of FOLFIRINOX (folinic acid, fluorouracil, irinotecan, and oxaliplatin) were administered, and radiologic improvement was evident on computed tomography angiography (Figure 3). After 8 months, the patient underwent a classical Whipple procedure. Pathological analysis confirmed metastatic colorectal adenocarcinoma with mucinous features, vascular and perineural invasion, negative margins, and no lymph node involvement (0/14) (Figure 4).

Recovery was uneventful, and follow-up over 5 months demonstrated good clinical progress (Figure 5).

Discussion

The most common sites of metastasis in colorectal cancer are the liver and lungs. Surgical resection of these metastases in selected patients is robustly associated with improved outcomes and, in some cases, cure [3,4]. In contrast, CRPM is rare, and the impact of surgical treatment on clinical outcomes remains unclear [5].

Pancreatic tumors are most commonly primary in origin, and metastatic lesions are rare, representing 1% to 2% of all pancreatic carcinomas; these may be solid or cystic in nature [6–8]. The existing literature more frequently describes metachronous pancreatic metastasis from renal cell carcinoma, often with a prolonged interval between resection of the primary tumor and the development of pancreatic metastases [6]. These metastases may occur as widespread disease or an isolated pancreatic lesion [9–11]. Isolated cystic metastasis to the pancreas from a colorectal primary (ICMCR) has rarely been reported; most available data are derived from autopsy studies, case reports, and small case series [6,12].

Only a limited number of reports describe the surgical management and clinical outcomes of patients with ICMCR, and most lack detailed descriptions of nonsurgical management. Pancreatic resection was reported in 2 consecutive series by Sperti et al for synchronous colorectal pancreatic disease [10,11]; however, none of these cases were described as ICMCR. Although these cases demonstrated favorable outcomes, with a median survival of 16.5 months, distinct adjuvant therapy protocols were used postoperatively.

Most reported cases of secondary pancreatic cancer, regardless of the primary tumor origin, have been managed with surgical resection when feasible. Neoadjuvant chemotherapy is known to downstage pancreatic neoplasms, allowing complete surgical resection in initially inoperable, borderline resectable, and locally advanced pancreatic cancer [13–15]. However, its role in CRPM remains unclear. In the present case, neoadjuvant chemotherapy achieved successful downstaging, enabling subsequent surgical resection without complications. Long-term follow-up and increased reporting of similar cases are needed to clarify the efficacy of neoadjuvant chemotherapy in locally advanced CRPM and ICMCR. Although pancreatectomy was previously avoided due to high morbidity and mortality rates, recent evidence suggests improved overall survival when resection is performed with curative intent. Given declining complication rates in high-volume centers, surgical intervention is increasingly justifiable in cases of resectable secondary pancreatic metastasis. High-volume centers reporting pancreatic resection for metastases from various non-colonic primary sites have demonstrated median survival of 4.6 years [16], as well as overall survival rates of 62% at 2 years and 25% at 5 years [17].

Due to limited evidence, there is no consensus or established guideline for the management of ICMCR. This is largely attributable to the rarity of the condition and the absence of comparative studies evaluating surgical versus conservative or palliative approaches. In this context, the present case provides additional insight concerning the role of a multidisciplinary approach in this uncommon setting. Our patient’s favorable treatment response and good postoperative outcome highlight the potential applicability of this approach in selected cases.

Conclusions

This case highlights challenges in the management of secondary pancreatic cancer arising from a colorectal primary, an area in which evidence remains limited. Surgical resection continues to represent the cornerstone of treatment for pancreatic tumors, irrespective of origin; it is associated with improved palliation and more favorable survival outcomes [8]. Similarly, in colorectal cancer metastases – most commonly involving the lung and liver – surgical resection has been shown to improve overall and disease-free survival [3,4]. However, given the rarity of CRPM, standardized treatment guidelines have not been established. The present report underscores the importance of a multidisciplinary approach and the need for further studies with refined patient selection to clarify optimal evidence-based management strategies.