The parotid gland, an unusual site of colorectal cancer metastasis

Colorectal cancer commonly metastasises to the liver, peritoneum and lungs. With dis-seminated disease, it can spread to more unusual sites. Parotid gland metastasis usually originates from head and neck malignancies. We present a case of stage IV sigmoid colon adenocarcinoma with metastases to the left parotid. The patient was a 53-year-old Filipino man diagnosed with stage IV sigmoid adenocarcinoma with liver metastases in June 2021. He underwent laparoscopic sigmoidectomy and received eight cycles of chemotherapy with capecitabine and oxaliplatin with partial response of his liver lesions. Capecitabine monotherapy was then maintained. On September 2022, he experienced persistent left facial pain, with no relief after dental tooth extraction and antibiotics. A computed tomography (CT) scan revealed a 5 x 7 x 6 cm inhomogenous mass in the left parotid with destruction of the mandible. A fine needle biopsy was consistent with a high-grade carci-noma. After multidisciplinary discussions, a repeat core needle biopsy was deemed necessary to proceed with immunohistochemistry. With strong positivity for cytokeratin 20 (CK20), carcinoembryonic antigen, special AT-rich sequence-binding protein 2 and CAM 5.2, and weak positivity for CK7, the parotid mass was diagnosed as metastatic adenocarcinoma from the colon. He then received palliative radiation to the parotid mass for pain con-trol. A gastrostomy tube was also inserted for nutritional support. Treatment with next-line chemotherapy (FOLFIRI regimen) was planned. Unfortunately, he contracted COVID-19 pneumonia and succumbed to respiratory failure. Pursuing the histologic diagnosis of this uncommon area of metastasis was necessary for appropriate treatment planning. Fostering multidisciplinary collaboration throughout the complex aspects of cancer care requires patient advocacy, leadership and effective communication. For our patient, it was essential to coordinate with surgery and pathology to maximise the diagnostic yield of a repeat biopsy while minimising complications and treatment delays.