Aberrant Presentation of Metastatic Colorectal Cancer: A Diagnostic Dilemma

Aliasger A Amin, Anil Reddy, Madan Jha. James Cook University Hospital

Objective: A 75 year old gentleman with 2-3 months history of an increased frequency of loose stools with occasional blood spotting. He had no other significant symptoms. Colonoscopy showed an obstructing lesion in the sigmoid colon and the biopsy confirmed to be adenocarcinoma. CT scan showed the sigmoid tumour with metastasis to the liver, retroperitoneal lymph nodes and left adrenal gland. Tumor was stented prior to starting chemotherapy. Five months later, he developed numbness over his right lower lip and jaw, and a swelling in the right mandibular region. On examination there was a mass in the right mandibular region. There was right mental nerve anaesthesia but no facial nerve palsy.

Method and procedure: He had a CT scan of his facial region and a trucut biopsy of the mass in the right mandibular region

Result: CT scan showed a 33.0mm mass with destruction of lingual and buccal cortex of the ascending ramus of mandible on the right side which extended to involve the region of the inferior alveolar canal involving the inferior alveolar nerve. Trucut biopsy was focally positive for CK20 and monoclonal CEA, which was consistent with metastatic adenocarcinoma suggestive of an origin from a primary colorectal cancer

Conclusion: Metastasis to mandible from adenocarinoma of the colon is quite rare and represents incurable disseminated disease. Most cases of mental nerve neuropathy that are not dental in origin have been associated with malignant tumors or diffuse metastatic disease. The sign of mental nerve neuropathy should be considered as a sinister symptom and clinicians should be aware of mandible being a potential site of metastasis from colorectal cancer and such cases should be further investigated accordingly.