A case of long-term recurrence-free poorly differentiated neuroendocrine carcinoma of lymph nodes treated by surgical resection without any chemotherapy.

A 77-year-old man presented with a 2-month history of an enlarged right inguinal lymph node. Diagnostic excisional biopsy of the inguinal lymph node proved it to be a poorly differentiated neuroendocrine carcinoma by histological and immunohistological analyses. We diagnosed a poorly differentiated neuroendocrine carcinoma by histological examination and immunohistological analysis of the resected inguinal lymph node. We performed computed tomographic examination and positron emission tomography, which identified lymph node involvement without any signs of other tumors. Because these tumors had grown expandingly and had been encapsulated locally, we performed an operation to dissect all of the involved lymph nodes. Direct invasion to the right external iliac artery was not detected, and two of the enlarged lymph nodes were successfully resected without any complications. Pathologically, the resected specimen was diagnosed as a neuroendocrine carcinoma with a negative surgical margin and it was similar to the histology of the inguinal lymph node previously resected. The patient had no recurrence for 3 years without receiving any adjuvant treatment. There have been no reports describing a case of poorly differentiated neuroendocrine carcinoma, of unknown origin, which metastasized to other lymph nodes. Although further studies are required, complete resection of the involved lymph nodes should be considered as a choice for localized, expanding growth-pattern disease even if it is undifferentiated type.