Esophageal carcinoma cuniculatum: a narrative review to understand this rare and commonly misdiagnosed variant of well-differentiated esophageal squamous cell carcinoma

Background and Objective: Esophageal carcinoma cuniculatum (CC) is a rare variant of a well-differentiated squamous cell carcinoma (SCC). Unlike other forms of esophageal cancers, CC of the esophagus is difficult to diagnose on endoscopic biopsies. This can lead to a delay in the diagnosis and increases morbidity. We reviewed the available literature to shed light on the etiopathogenesis, diagnosis, treatment, and outcomes of this disease. Our aim is to create a better understanding of this rare disease entity and contribute to a timely diagnosis to reduce the associated morbidity and mortality. Methods: Extensive review of PubMed, Embase, Scopus, Google Scholar was conducted. We identified the published literature on Esophageal CC from inception till date. We report epidemiological trends, clinical presentation, diagnostic and treatment strategies to correctly identify the cases to reduce the likelihood of a missed diagnosis of esophageal CC. Key Content and Findings: Associated risk factors for esophageal CC are chronic reflux esophagitis, smoking, alcohol consumption, immunosuppression, and achalasia. Dysphagia is the most common presentation. Primary diagnostic modality is an esophagogastroduodenoscopy (EGD), but diagnosis can be easily missed. To favor an early diagnosis, a histological scoring system has been proposed by Chen et al. where authors describe specific histological features that appear to be common based on the numerous mucosal biopsies examined from patients with CC. Conclusions: A high clinical suspicion for the disease along with close endoscopic follow-up with repeat biopsies is needed for an early diagnosis. Surgery remains the gold standard for treatment and is associated with a favorable prognosis when the patients are diagnosed early.