Low Grade Sinonasal Adenocarcinoma

Sinonasal adenocarcinoma is a rare neoplasm which is classified as ‘intestinal' or ‘nonintestinal' type, depending on its resemblance to gastrointestinal mucosa. These tumors are associated with occupational and environmental carcinogens. In this study, a fifty-year-old oil-painter male patient with a low-grade nonintestinal type sinonasal adenocarcinoma originating from the left middle concha and ethmoid sinus is presented. Microscopical examination revealed many infiltrative glandular structures, most of which were cystically dilated and some of which were smaller in diameter, arranged back to back in loose fibrous stroma as well as intraglandular papillary and micropapillary structures forming complex branches or a cribriform pattern. The glands were lined by epithelial cells that were faintly eosinophilic and relatively abundant cubical/ cylinderical cytoplasms and mildly pleomorphic round/oval nuclei, with rare mitotic figures. Intraluminal and focally intracytoplasmic mucin was demonstrated with Alcian Blue, mucicarmin and PAS stains. Immunohistochemically, tumor cells were strongly and diffusely positive with CK7; focally and weakly positive with CK20 and negative with CDX2 in accordance with the nonintestinal type. S-100, Actin and p63, applied for investigating the myoepithelial and salivary glandular origins, were all negative. Prognostic markers, TTF-1 and p53 were negative; while the Ki-67 index was 2%. The fact that intestinal type sinonasal adenocarcinomas are generally high grade, while nonintestinal tumors are histologically low grade makes this morphological and immunohistochemical-based classification valuable in predicting the prognosis of the disease. In addition to the morphological and immunohistochemical findings, clinical information stands out in the differentiation of the tumor from benign or malignant primary lesions or metastatic adenocarcinoma.