ABSTRACT
The authors describe a patient whose nasal neoplasm demonstrated histological characteristics of both a moderately differentiated intestinal-type adenocarcinoma and an atypical carcinoid (well-differentiated neuroendocrine carcinoma). The adenocarcinoma displayed a predominantly papillary architecture, immunohistochemically positive staining for intestinal markers, and ultrastructural features (microvilli with long roots) characteristic of intestinal differentiation. The carcinoid component was argyrophilic, was immunoreactive with chromogranin, gastrin, and serotonin, and displayed ultrastructurally characteristic G and EC cells. The neoplasm recurred twice, and the tumor tissue from the second recurrence was composed only of neuroendocrine cells, indicating that this component was more resistant to the therapy (surgery and radiotherapy) employed. The patient died from an intracranial recurrence 5 months after the last combined surgical and radiotherapic treatment. Because of its unfavorable prognosis, a neuroendocrine-exocrine tumor should not be grouped with typical carcinoids or with well-differentiated papillary sinonasal adenocarcinomas, which seem to be less aggressive.