Biphasic large cell neuroendocrine carcinoma--pure mucinous carcinoma of the gallbladder (MANEC): a unique combination.

[carcinoma of the gallbladder]

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 .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 .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 CD 5 6 were diffusely and strongly expressed .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 .