A Case of Sinonasal Intestinal Type Adenocarcinoma Mimicking CNS Tumour: A Pathologist’s Perspective

Sinonasal Intestinal-Type Adenocarcinoma (ITAC) is a rare neoplasm. The overall incidence of ITAC is less than 1% of all neoplasms, but almost 4% in sinonasal malignancies. This tumour tends to be very locally aggressive but rarely metastasises. It is frequently misdiagnosed clinically as a salivary gland tumour or Central Nervous System (CNS) tumour. In this case, a 50-year-old female presented with chief complaints of headache, vomiting and occasional nasal bleed for a few months. Radiological diagnosis (MRI) of CNS tumour was made. The other relevant necessary investigations and clinical management was done as per surgical oncology team. The tumour was removed by bifrontal craniotomy. On histopathological examination, two differential diagnoses of metastatic Gastrointestinal (GI) adenocarcinoma and sinonasal ITAC were made. Tumour cells exhibited strong immunopositivity for CK-20, CDX2, and Epithelial Membrane Antigen (EMA), while being negative for Glial Fibrillary Acidic Protein (GFAP). Thus, the final diagnosis made was well-differentiated sinonasal adenocarcinoma of the intestinal type. This case highlights the importance of histopathology with Immunohistochemistry (IHC) when most probable clinical as well as radiological diagnosis was CNS tumour. Histopathological examination with a combination of IHC had confirmed the diagnosis of sinonasal ITAC.