Metastasis to the sinonasal tract from sigmoid colon adenocarcinoma

Metastatic adenocarcinoma from the gastrointestinal tract to the sinonasal tract is rare. The histological morphology of this lesion is indistinguishable from the colonic variant of primary sinus adenocarcinoma or intestinal-type adenocarcinoma (ITAC). This is a report of a case of metastatic adenocarcinoma of colorectal origin to the paranasal sinuses in a 52-year-old female who was previously treated for adenocarcinoma of the sigmoid colon. A histologic study of the surgical specimen from the sinonasal cavity demonstrated a tumour identical to the patient's prior primary tumour of the colon. The sinonasal neoplastic tissue showed marked positivity for carcinoembryonic antigen and expressed cytokeratin 20, which differentiates metastatic colonic adenocarcinoma from ITAC. The patient received palliative radiation but died 3 months after the diagnosis. Distinguishing metastatic adenocarcinoma from gastrointestinal tract from ITAC can be difficult. In view of the resemblance, immunohistochemical staining can help in differentiating them. It is important to recognise these as metastatic lesions as the treatment is mainly palliative.