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Esophageal benign lesions have been detected less often than malignant lesions, accounting for only 0.5% of autopsy cases, because most patients are asymptomatic . However, benign esophageal lesions can be detected more often by the widespread use of endoscopes and an increasing awareness of the disease. Sebaceous glands are normally found in human hair follicles, but ectopic areas have been reported around the eyes and in the oral cavity, tongue, larynx, palms, soles, and external genitalia, which are lined with squamous cells. Sebaceous glands in the esophagus were first reported in 1962 by De La Pava and Pickren  and are rarely found. The apparent low incidence of this condition may be because of the lack of obvious clinical signs and symptoms. Most cases were discovered incidentally by endoscopy in patients referred for gastrointestinal tract examination.
Ectopic sebaceous glands (ESGs) are best distinguished from other yellowish plaques such as xanthoma through endoscopy. Esophageal xanthomas were first reported in 1984 by Remmele and Engelsing . One study showed that the most common location of xanthoma was the stomach (76%), followed by the esophagus (12%) and sphingosine 1-phosphate receptor modulator (12%) . Coincidently, both ESGs and xanthomas are detected in the lower esophagus and should be confirmed via tissue biopsy.
ESGs and xanthomas in the esophagus (Figure 5) have similar epidemiology, such as patient age (mean, 50 years), endoscopic features (yellowish, small, mildly elevated lesions), and clinical symptoms (asymptomatic), with good prognoses. To the best of our knowledge, no case reports have discussed their differences. We present three cases of ESGs and one case of xanthoma in the esophagus that had similar endoscopic findings and age distributions. A comparison between the esophageal ESGs and xanthoma is provided in Table 1.
ESGs and xanthomas are rarely found in the esophagus. For ESGs in the esophagus, the typical mean patient age at onset is 50 years, with almost equal distribution in men and women . For esophageal xanthoma, also known as “xanthelasma” and “lipid island,” the mean patient age at onset is 54 years, with mild predominance in men [6,7]. ESGs are most likely the result of a metaplastic process rather than a congenital anomaly. As ESGs are derived from endodermal tissue, it is unlikely that they are derived from ectodermal tissue . ESGs are rarely found in infants or children, supporting the belief that they are less likely to be a congenital anomaly ; rather, ESGs are suspected to be associated with reflux gastritis. Accordingly, the theory of an acquired metaplastic change of the esophageal epithelium was suggested in a 79-year-old man . Only one of our patients had gastroesophageal reflux disease. All the patients were diagnosed with ESG in the lower esophagus. In our opinion, the theory of acquired metaplastic change is possible, but there is not enough evidence to support it.
The etiology of esophageal xanthomas is still unknown. One study reported a theory that gastric xanthoma is derived from focal mucosal damage in which the lipids were derived from broken-down cell membranes and captured by interstitial histiocytes . This may explain why the esophageal mucosa has a better tolerance to damage than the gastric mucosa and the fewer reports of xanthoma in the esophagus . No significant associated clinical symptoms or signs have been reported.
For ESGs in the esophagus, the number of occurrences has ranged from 1 to more than 100 (which was consistent with the findings in our patients), and lesion sizes have ranged from 1 mm to 20 mm, with the majority of cases being smaller than 0.5 cm . Factors that affect the pattern and distribution of ESGs in the esophagus require further study. They have several different shapes and a yellowish appearance; smaller lesions are flat or dome shaped, or have a papular surface with irregular margins. Esophageal xanthomas are located most often in the lower esophagus and are about 2–10 mm in size . They appear as well-defined, fern-like yellowish plaques scattered over the middle or lower esophagus, with the plaques being composed of clusters or groups.
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