A Rare Case of Metastatic Merkel Cell Carcinoma to the Stomach and Pancreas Presenting With Upper Gastrointestinal Bleeding and Obstructive Jaundice

Metastasis to the stomach: a systematic review

Background: This study reviews the literature on gastric metastases (GM) in terms of diagnosis, treatment, and outcomes. The goal of this study was to provide clinicians with a reliable and beneficial source to understand gastric metastases arising from various primary tumors and to present the growing literature in an easily accessible form. Methods: Articles published in English language from implementation of MEDLINE and Cochrane databases until May 2022 were considered for the systematic review. Articles other than English language, letters to the editor, posters, and clinical images were excluded. Hematogenous and lymphogenic metastases were included whereas direct tumoral invasion and seeding were excluded. Articles and abstracts were analyzed and last selection was done after cross-referencing and by use of defined eligibility criteria. Results: In total 1,521 publications were identified and 170 articles were finally included totaling 186 patients with GM. The median age of patients was 62 years. Gynecologic cancer was the most common cancer type causing GM (67 patients), followed by lung cancer (33 patients), renal cancer (20 patients), and melanoma (19 patients). One of the main treatment methods performed for metastasis was resection surgery (n=62), sometimes combined with chemotherapy (ChT) or immunotherapy. ChT was the other most used treatment method (n=78). Also, immunotherapy was amongst the most preferred treatment options after surgery and ChT (n=10). Conclusions: As 172 case reports were screened in the systematic review from different journals, heterogeneity was inevitable. Some articles missed important information such as complete follow-up or clinical information. Moreover, since all of the included articles were case reports quality assessment could not be performed. Among 172 case reports reviewed, resection surgery was performed the most and was sometimes combined with ChT and immunotherapy. Further research about what type of treatment has the best outcomes for patients with gastric metastases is needed.

Malignant biliary obstruction due to metastatic non-hepato-pancreato-biliary cancer

Malignant biliary obstruction generally results from primary malignancies of the pancreatic head, bile duct, gallbladder, liver, and ampulla of Vater. Metastatic lesions from other primaries to these organs or nearby lymph nodes are rarer causes of biliary obstruction. The most common primaries include renal cancer, lung cancer, gastric cancer, colorectal cancer, breast cancer, lymphoma, and melanoma. They may be difficult to differentiate from primary hepato-pancreato-biliary cancer based on imaging studies, or even on biopsy. There is also no consensus on the optimal method of treatment, including the feasibility and effectiveness of endoscopic intervention or surgery. A thorough review of the literature on pancreato-biliary metastases and malignant biliary obstruction due to metastatic non-hepato-pancreato-biliary cancer is presented. The diagnostic modality and clinical characteristics may differ significantly depending on the type of primary cancer. Different primaries also cause malignant biliary obstruction in different ways, including direct invasion, pancreatic or biliary metastasis, hilar lymph node metastasis, liver metastasis, and peritoneal carcinomatosis. Metastasectomy may hold promise for some types of pancreato-biliary metastases. This review aims to elucidate the current knowledge in this area, which has received sparse attention in the past. The aging population, advances in diagnostic imaging, and improved treatment options may lead to an increase in these rare occurrences going forward.

Merkel Cell Carcinoma With Isolated Pancreatic Metastasis

Merkel cell carcinoma (MCC) is a highly aggressive cutaneous neuroendocrine carcinoma, frequently associated with distant metastasis. However, recurrence of MCC manifesting with only pancreatic involvement is exceedingly rare. A 53-year-old man presented to our institution with abdominal discomfort 3 months after initial resection of chest wall MCC. Imaging revealed lesions in the pancreas and peripancreatic lymph nodes. Pathology obtained through endoscopic ultrasound confirmed recurrence of MCC. He underwent chemotherapy with cisplatin and etoposide, resulting in a complete resolution of the pancreatic lesions. Unfortunately, he passed away from sudden cardiac arrest while being in remission from MCC. Immunohistochemistry is crucial in differentiating MCC from primary pancreatic glandular and neuroendocrine tumors. While there are no definitive guidelines in the management of pancreatic lesions associated with MCC, checkpoint inhibitor immunotherapy is increasingly being used.