RESUMEN
BACKGROUND: The prevalence and incidence of neuroendocrine tumors (NETs) are increasing worldwide. Primary mesenteric NETs are extremely rare. Solid tumors that arise in the mesentery are typically metastatic. We present an extremely rare case of a primary grade 2 NET (NET G2) in the ileal mesentery. CASE PRESENTATION: A 54-year-old man was referred to our hospital for further examination of a previously diagnosed right mesenteric tumor. Mild tenderness was noted on the right side of the abdomen, but there were no palpable masses. Fluorodeoxyglucose-positron emission tomography (FDG-PET) revealed slight FDG uptake (maximum standardized uptake value, 2.0) in the right abdomen, and a benign or low-grade malignant tumor was suspected. We extracted the ileal mesenteric tumor with an ileal resection (90 cm). The cut surface of the 55 × 33 × 33 mm3 tumor was pale yellowish-white. Immunohistochemistry revealed diffuse staining for synaptophysin and chromogranin A, and focal staining for CD56. The Ki-67 index was 3%. The final pathological diagnosis was NET G2. The patient's postoperative course was uneventful, and he developed no recurrence 1.5 years after surgery. Postoperative antitumor therapy was not performed for this patient because the histological diagnosis was NET G2, and it was determined that the tumor could be completely resected by surgery. CONCLUSIONS: We report an extremely rare case of primary ileal mesenteric NET. Mesenteric tumors that show slight FDG uptake on FDG-PET examination should be considered well-differentiated NET.
RESUMEN
OBJECTIVE: Recent technologic developments in computed tomography have increased the incidence of surgical intervention for small-sized lung cancer. Although indications of a sublobar resection for early disease have been discussed, we occasionally encounter locally advanced small-sized lung cancer with node metastasis. The present study aimed to clarify the histopathologic factors influencing nodal involvement and prognosis of such patients. METHODS: We studied 97 patients who underwent complete resection for an adenocarcinoma of 2 cm or less in diameter. Lymph node metastasis and necrosis were microscopically evaluated, whereas immunohistochemical studies were also performed with Ki-67 and D2-40 for proliferation activity and lymphatic invasion, respectively. In addition, carcinoembryonic antigen expression in the tumor and its level in serum were investigated. Survival analysis was then conducted by using these clinicopathologic factors. RESULTS: The 5-year disease-free survival rate was 90%. Nodal involvement was significantly frequent in patients with tumors showing microscopic necrosis, a Ki-67 labeling index of greater than 5%, and an increased serum carcinoembryonic antigen level. Furthermore, 5-year disease-free survival was worse in patients with lesions showing microscopic necrosis (68%), a Ki-67 labeling index of greater than 5% (76%), and lymphatic invasion detected with D2-40 staining (77%). Multivariate analysis identified lymphatic invasion detected with D2-40 to be an independent predictor for postoperative recurrence. CONCLUSIONS: These results indicate that microscopic necrosis, Ki-67 labeling index, and serum carcinoembryonic antigen level are predictors of nodal involvement. Careful postoperative follow-up examinations for recurrence are required for patients with tumors that show microscopic necrosis, high Ki-67 labeling index, and lymphatic invasion, even in those with stage IA disease.
