S4308 Caught Between Two Histologies: A Rare Case of Esophageal Primary Adenosquamous Carcinoma

Introduction: Adenosquamous carcinoma (ASC) of the esophagus is a rare type of esophageal cancer. Incidence rates are reported to range from 0.37% to 1% of all esophageal cancers. ASC has histological components of both adenocarcinoma (AC) and squamous cell carcinoma (SCC), and the pathogenesis is unclear, with theories suggesting an AC origin that progresses to SCC, SCC which then undergoes glandular differentiation, or ASC which arises from 2 simulation stem cell mutations that undergo malignant transformation. We present a case of ASC in an elderly gentleman. Case Description/Methods: Our patient is an 86-year-old man with a remote history of prostate cancer who presented to the office with complaints of reflux. His symptoms were previously well controlled on pantoprazole for a few years. Three months prior to arrival he experienced seizures and was started on levetiracetam and lamotrigine by neurology. Following this, he began to experience dysphagia with solid and liquid foods. He was started on omeprazole which he was unable to swallow. His seizure medications were switched to valproic acid only, and his pantoprazole was resumed; however, his symptoms continued to persist. On arrival to the office he had unintentional weight loss of 11 pounds in 2 weeks. He underwent esophagogastroduodenoscopy, which showed congested and vertically lined mucosa in his esophagus; he also had esophageal stenosis which was dilated. There was gastritis and congestion present in the stomach as well. Pathology of biopsies from the distal esophagus showed invasive ASC arising in the squamoglandular junction. He was referred to oncology and had a positron emission tomography scan which showed liver metastasis. He started chemotherapy with FOLFOX and herceptin and is currently following with oncology. Discussion: This case underscores the insidious nature of ASC and its difficulty in diagnosis. Treatment is complicated as surgery is preferred in local disease but diagnosis is often made in advanced stages. Prognosis data also seems to be conflicting. In a retrospective review, lymph node metastasis was found to be an important prognostic factor, and the prognosis was found to be no worse than when compared to esophageal SCC or AC. However, other comprehensive reviews found no independent prognostic factors. Comparisons of mean survival times and 5-year mortality between ASC and AC/SCC showed both no difference and lower survival in ASC in different articles. Given the difficulty in diagnosis and treatment, further research is needed.