Biphasic Large Cell Neuroendocrine Carcinoma--pure Mucinous Carcinoma of the Gallbladder (MANEC): a Unique Combination

Introduction: We report a case of primary combined large cell neuroendocrine carcinoma (LCNEC)--pure mucinous carcinoma of the gallbladder (MANEC)--which represents the first description of this entity.

Methods: The patient is a 59-year-old Italian male who underwent cholecystectomy under a preoperative diagnosis of cholecystitis with gallstones and gallbladder tumour. During laparotomy, cholecystectomy, liver wedge resection and regional lymph node dissection were performed. The resected gallbladder showed a thickened wall, gallstones and a 4 cm gelatinous, cauliflower-like soft tissue mass.

Results: Following surgery, the gallbladder tumour was diagnosed as a mixed endocrine-exocrine carcinoma. There was evidence of lymph node metastasis or direct liver invasion. The mucin-producing carcinoma was composed of poorly differentiated glandular cells with mucin lakes. The LCNEC was characterized by large cells with prominent nucleoli, coarse chromatin and a high mitotic rate. The cells showed an "organoid" growth pattern with rosette formation and frequent areas of necrosis. Chromogranin A, synaptophysin and CD56 were diffusely and strongly expressed.

Discussion: This case may provide helpful insights regarding the histogenesis of this unusual combination of tumors: the concept of a collision tumor between two neoplasms that have arisen in adjacent areas may be the best explanation for its pathogenesis.