The patient is a 53-year-old Filipino man diagnosed with sigmoid adenocarcinoma with de novo liver metastasis in June 2021. He initially underwent laparoscopic sigmoidectomy to relieve his partial gut obstruction. Although it is not the recommended first-line treatment for metastatic colon cancer, the patient was then treated with capecitabine at 1,250 mg/m2 twice a day for 14 days and oxaliplatin at 130 mg/m2 at 21-day cycles. Due to financial constraints and lack of local reimbursement, molecular testing for kirsten rat sarcoma viral oncogene homolog, neuroblastoma RAS viral oncogene homolog, v-raf murine sarcoma viral oncogene homolog B1 mutations and mismatch repair deficiency or microsatellite instability was not pursued. Furthermore, additional targeted treatments such as Cetuximab or Bevacizumab or immunotherapy are an out-of-pocket expense locally. After eight cycles of capecitabine and oxaliplatin, a partial response by response evaluation criteria in solid tumors criteria of his liver lesions was achieved despite a minimal increase in his carcinoembryonic antigen (CEA) (42 ng/mL) from baseline (33 ng/mL). He was then maintained on capecitabine monotherapy. On September 2022, he experienced persistent left facial pain, with no relief after dental tooth extraction and 2 weeks of oral antibiotics.
Despite the patient's rapidly growing left facial mass (Figure 1a), consultation with his medical oncologist was delayed due to inadequate health-seeking behaviour and financial difficulties. A neck and oral cavity contrast-enhanced CT scan revealed a 5 x 7 x 6 cm inhomogenous mass in the left parotid with osseous destruction of the mandible (Figure 1b).
Fine needle biopsy of the mass showed papillary, solid and disorganised glandular patterns with high-grade nuclear features with pleomorphic nuclei - consistent with a high-grade carcinoma, and not purely adenocarcinoma (Figure 2a and b). A repeat chest and abdominal contrast-enhanced scan also revealed progression of his liver lesions (multiple enhancing inhomogenous masses with the largest progressing in size, now measuring 7 x 5 cm from 4 x 5 cm previously). Differential diagnoses of the new parotid malignancy included metastatic adenocarcinoma from the colon as well as a new head and neck primary malignancy, particularly, a mucoepidermoid carcinoma of the parotid gland. Despite concerns regarding poor prognosis, the patient and his team of doctors agreed that a correct diagnosis and proper palliative treatment must be pursued. After multidisciplinary meetings with surgery, radiation oncology and pathology, a repeat biopsy through a core needle was deemed necessary to proceed with immunohistochemistry stains. With strong positivity for cytokeratin 20 (CK20), special AT-rich sequence-binding protein 2 (SATB2) and CAM 5.2, and weak positivity for CK7, the parotid mass was diagnosed as a metastatic adenocarcinoma from the colon.
He then received palliative local radiation at 20 Gy given in five fractions for pain control. A gastrostomy tube was also inserted for nutritional support. With a fair performance status at a Karnofsky grade of 70, treatment with FOLFIRI (combination chemotherapy with 5-fluorouracil, leucovorin, and irinotecan) was then planned. However, the patient contracted severe COVID-19 pneumonia before starting treatment and eventually died of respiratory failure after 3 weeks of hospital admission.