Metachronous Lower GI Malignancies in Head and Neck Squamous Cell Carcinoma: A Case Report and Literature Review

Second primary gastrointestinal (GI) adenocarcinoma is rare in a previously treated or untreated primary head and neck squamous cell carcinoma (HNSCC). We present a case of metachronous colon adenocarcinoma in a primary oropharyngeal squamous cell carcinoma (SCC) post-treatment. An elderly patient with stage IVA primary SCC involving the base of the tongue and adjacent tonsil has been successfully treated with definitive concurrent chemoradiotherapy using weekly cisplatin in our tertiary care center. Approximately, 3 years post-treatment, she has been diagnosed with second primary adenocarcinoma involving the right-sided colon. This metachronous malignancy has been treated by surgery followed by adjuvant chemotherapy. After our case presentation, we reviewed the literature onmetachronous malignancies in primary HNSCC and also about colorectal cancers as a second primary malignancy with their impact on survival.