Gallbladder neuroendocrine neoplasm: a case report and critical evaluation of WHO classification.

Gallbladder neuroendocrine neoplasms (GB-NENs) are rare. The majority of GB-NENs are poorly differentiated, with increased mitotic activity and clinically aggressive course. Surgery is the only curative approach and the optimal medical treatment is uncertain. In this report we describe the case of a woman affected by metastatic well differentiated GB-NEN with increased Ki 67. The patient underwent surgical removal of the gallbladder neoplasm and showed disease recurrence with pulmonary and liver metastases. After achieving a partial chemotherapy response, the patient rapidly died due to progressive disease. This case raises important issues. Well differentiated NENs with a high proliferative index are not included as a specific entity in any of the most widely used nomenclature systems. Moreover considering the proliferative index of the disease, it is reasonable to consider the patient a candidate for chemotherapy. Nevertheless, recently published papers raise the possibility that well differentiated NENs and specific proliferative index cutoff can predict low chemosensitivity in patients with highly proliferative neuroendocrine carcinoma.