Sinonasal Low-Grade Adenocarcinoma: Report of Three Cases with the Clinicopathologic and Immunohistochemical Findings

Low-grade adenocarcinomas that primarily arise within the sinonasal tract are uncommon tumors. We report here on three cases of primary sinonasal low-grade adenocarcinomas. The patients were 2 females and 1 male with ages of 48, 57 and 64, respectively. Microscopically, the tumors had a well developed tubulopapillary growth pattern that consisted of columnar or pseudostratified cells with eosinophilic cytoplasm, round to oval nuclei and rare mitotic activity. On immunohistochemistry, the tumor cells were strongly positive for cytokeratin 7, but they were negative for cytokeratin 20, CDX-2 and p53. The Ki-67 labeling index was very low (mean: 1.9%). Two patients developed recurrent tumors at the primary site after the initial surgery, but all the patients are presently alive without metastasis 6 years 8 months, 8 years 8 months, and 11 months after the initial diagnosis. When considering the progress of these tumors, we think that it’s important to understand the pathology of this entity to avoid underdiagnosis because a complete excision is required for effective treatment.