Surgical resection of isolated pancreatic metastatic malignant melanoma

Pancreatic metastasis from a nonpancreatic primary tumor is rare (<2 %) (1,2) and has a potentially poor prognosis (3). Melanoma is an aggressive skin malignancy that commonly exhibits distant metastasis and poor overall prognosis (4). Isolated pancreatic metastasis from melanoma is even less common and poses significant diagnostic and therapeutic challenges. A retrospective study demonstrated that surgical resection increased the survival of patients with abdominal visceral melanoma metastases (5). However, pancreatic resection of metastatic melanoma is potentially associated with high mortality as experience with this type of surgery is limited (6). Here, we describe a rare case of isolated pancreatic metastatic melanoma treated with pancreatic resection at our hospital, including clinical features, treatment, and follow-up. A review of the related literature is also provided.

A 72-year-old Chinese woman underwent routine examination at our hospital, which revealed a hypoechoic mass in the pancreas on abdominal ultrasonography (Figure 1A). Subsequent abdominal contrast-enhanced computed tomography (CT) revealed a 22 mm × 13 mm lesion in the body and tail of the pancreas, which was confirmed by magnetic resonance imaging (MRI) (Figure 1B,1C). The patient had undergone surgical resection for malignant melanoma at the left skull base in our hospital 26 months earlier. After surgery, the patient received sequential treatment, including cisplatin combined with temozolomide chemotherapy and radiotherapy, as well as sintilimab and toripalimab immunotherapy. Positron emission tomography (PET)-CT revealed a pancreatic body mass with heightened ¹⁸F-fluorodeoxyglucose (FDG) metabolism (Figure 1D) and postoperative alterations in the left nasal skull base melanoma, as indicated by localized FDG uptake near the left maxillary frontal process and nasolacrimal duct. Laboratory assessments demonstrated normal blood cell counts and typical ranges in the levels of the carcinoembryonic antigen (CEA) and carbohydrate antigen 19-9 (CA19-9) tumor markers.

Figure 1 Ultrasound, CT, MRI, and PET-CT images of tumor in the pancreas (yellow arrowhead). (A) Ultrasound shows hypoechoic areas within the pancreas. (B) CT shows enhancement of pancreatic body and tail tumors during arterial phase. (C) Coronal MRI shows the location of the tumor in the pancreas. (D) Significantly enhanced FDG uptake in pancreatic lesions on PET-CT. CT, computed tomography; MRI, magnetic resonance imaging; PET, positron emission tomography; FDG, fluorodeoxyglucose.

We performed pancreatic body and distal resections combined with a splenectomy using the da Vinci robotic system to completely remove the tumor (Figure 2). No other abdominal metastases were observed intraoperatively, and pathological evaluation confirmed the integrity of the tumor. The patient was discharged smoothly after 3 weeks of treatment. Histopathological examination of the specimen revealed the presence of malignant melanoma with necrosis and a tumor size of 3 cm × 3 cm × 2 cm. The pancreatic margin was negative, and no involvement of the spleen was observed (Figure 3A,3B). Immunoreactivity was strongly positive for anti-HMB45 (Figure 3C) and weakly positive for anti-S-100 protein (Figure 3D). Tumor cells tested negative for CK7/18/19, CAM5.2, CD56, and D2-40. The Ki-67 index was approximately 80%. Immunohistochemical analysis revealed findings consistent with those obtained 2 years prior (Figures 3,4), thereby substantiating the diagnosis of pancreatic metastatic malignant melanoma. Notably, a neuroendocrine tumor measuring approximately 2.5 mm in maximum diameter (Figure 5) was classified as G1 stage. The patient was discharged after 3 months. Routine blood tests and evaluation of the CEA and CA19-9 tumor marker levels showed no significant abnormalities. The patient is currently undergoing regular follow-ups.

Figure 2 Photos of surgical specimens. The spleen, omental tissue, and pancreatic tissue including tumors (yellow arrowheads) are shown.

Figure 3 HE staining and immunohistochemical images of the pancreatic metastatic malignant melanoma. (A) HE staining of the pancreatic metastatic malignant melanoma at 4× magnification. (B) HE staining of the pancreatic metastatic malignant melanoma at 40× magnification. (C) Immunohistochemistry shows positive HMB45 staining at 40× magnification. (D) Immunohistochemistry showing positive S-100 staining at 40× magnification. HE, hematoxylin and eosin.

Figure 4 HE staining and immunohistochemical images of the primary tumor. (A) HE staining of the primary malignant melanoma at 4× magnification. (B) HE staining of the primary malignant melanoma at 40× magnification. (C) Immunohistochemistry showing positive HMB45 staining at 40× magnification. (D) Immunohistochemistry shows weakly positive S-100 staining at 40× magnification. HE, hematoxylin and eosin.

Figure 5 HE staining and immunohistochemical images of the neuroendocrine tumor. (A) HE staining of the neuroendocrine tumor at 4× magnification. (B) HE staining of the neuroendocrine tumor at 40× magnification. (C) Immunohistochemistry showing positive CgA staining at 40× magnification. (D) Immunohistochemistry shows positive Syn staining at 40× magnification. HE, hematoxylin and eosin.

Pancreatic metastatic lesions are extremely rare in pancreatic malignancies and are usually observed in patients with widespread primary carcinoma metastases. Isolated pancreatic metastatic lesions are even more uncommon (1). The most common malignant tumors that metastasize to the pancreas are renal cell carcinoma, lung cancer, breast cancer, and colon cancer; malignant melanomas are less common (1,7). Malignant melanoma is a relatively common malignant tumor of the skin, mucous membranes, and pigmented tissues, with a high incidence of metastasis to the small intestine, colon, stomach, and rectum. Reports of pancreatic metastatic malignant melanoma are rare (5,8). Despite continuous advancements in treatment, the prognosis for these patients remains poor owing to the high malignancy and early metastasis of these tumors. According to a previous study, the 5-year overall survival rate of patients with melanoma in China is 41.6%, with a median survival time of 3.92 years. For patients diagnosed with stage IV disease, the 5-year survival rate is only 4.6%, with a median survival time of 1.42 years (9).

Currently, no consensus on the treatment of metastatic malignant melanoma exists, and many factors affecting the survival rate of these patients remain unknown. Deutsch et al. (5) conducted a retrospective study on patients with stage IV malignant melanoma, including those with abdominal organ metastases. Among these, pancreatic metastatic melanoma accounted for 2.3%. They found that patients with malignant melanoma metastasizing to the gastrointestinal tract, liver, spleen, pancreas, or multiple abdominal organs had higher survival rates after surgical treatment compared with those who did not undergo surgery. With the recent advent of systemic treatments, the advantages of surgical treatment have become more apparent, with the median survival time increasing from 8 to 11 months.

Although some evidence have suggested that surgical resection of metastatic malignant melanoma benefits patient survival, experience with surgical resection of pancreatic metastatic melanoma remains limited. Goyal et al. (1) reported a median survival period of 11.4 months and longest survival time of 26 months for five patients who underwent surgical resection. However, three of these patients experienced varying degrees of postoperative complications. He et al. (8) reported a case of pancreatic metastatic malignant melanoma that was successfully treated with surgical resection, resulting in a survival time of 25 months and no local recurrence or other metastatic lesions.

At The Second Affiliated Hospital and Yuying Children’s Hospital of Wenzhou Medical University, we identified a patient with isolated pancreatic metastatic melanoma. Through imaging examinations such as PET-CT, we found that the patient had no other metastatic lesions. After a thorough preoperative evaluation and multidisciplinary treatment consultation, we performed surgical resection of the lesion using the da Vinci robotic-assisted system. Postoperative pathological examination confirmed the complete removal of the lesion. The patient has been followed up for 3 months, and no significant postoperative complications have been observed. This case provided further evidence for the surgical treatment of isolated pancreatic metastatic melanoma. Based on a comprehensive assessment, we believe that surgical resection can improve the prognosis of such patients. Additionally, this is the first study to propose the use of da Vinci robotic-assisted surgery for the resection of isolated pancreatic metastatic melanoma. The pancreas is an anatomically complex organ with intricate vascular structures, and the da Vinci robotic system can enhance the stability and safety of the surgery. However, owing to the limited number of reported cases, further research is needed.

Acknowledgments

Funding: None.

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