This is a rare case report of thoracoscopic esophagectomy for ESCC after POEM for esophageal achalasia. The first report on the relationship between ESCC and esophageal achalasia was published in 1872 . The incidence of esophageal achalasia estimated to be 0.5–1.6 cases in 100,000 individuals per year [6, 7], with 0.4–9.2% of all cases suffering from ESCC . Esophageal achalasia was mainly managed with pneumatic dilation, and Heller myotomy (HM) before POEM, which entails incision of the inner circular muscle through a submucosal tunnel around the EGJ, was introduced by Inoue in 2009 as a novel and effective treatment option with less invasiveness . Recent studies have compared POEM with other methods for the treatment of esophageal achalasia. Steven G and Fraukje A have reported that although POEM is associated with a high incidence of reflux esophagitis, which can be controlled by proton pump inhibitors, it is superior to pneumatic dilation and HM in terms of long-term therapeutic effects as evaluated by the Eckardt score [9, 10]. Therefore, POEM is now becoming one of the most common standard procedures to treat esophageal achalasia.
In the present case, the pathological assessment of the surgical specimen revealed that nearby 75% of the inner circular muscle was lost at the EGJ level, which extended along the 2 o’clock direction toward the oral side of the entry hole. As shown in Fig. 6, the loss in the outer longitudinal muscle, as well as atrophied inner circular muscle, could also be detected along this area. The observed loss and atrophy resulted from the muscular incision made during POEM to relieve the LES pressure and improve the esophageal passage.
In general, only the inner circular muscle is incised when the EGJ is approached through the mucosal entry in the course of POEM. Although the smooth muscles have the ability to regenerate , there was nearby 75% muscle loss in addition to the presence of some atrophic areas in the inner circular muscle at the EGJ level; these changes were more extensive than the incised site by POEM. Barry and Aymeric reported that muscle incisions caused muscular atrophy along the fiber direction in the rabbit gastrocnemius [12, 13]. This is because the rupture of the strong tension caused by esophageal achalasia at the EGJ leads to remarkable atrophy along the fiber direction of the inner circular muscle. The esophageal inner circular muscle was missing in tiers in some area, which might have caused by the bending and dilatation of esophagus from the cranial to the caudal side; this phenomenon might hinder the incision of the esophageal inner circular muscle in a straight line. This outcome might also have been caused by the discrepancy between the incisional line and the longitudinal axis of the esophagus during specimen incision because of the natural winding around the EGJ. There was a loss of the outer longitudinal and inner circular muscles along the submucosal tunnel. This is attributable to the decreased strength of the esophageal wall at the site of incision and the subsequent pressure that causes a tear in the outer longitudinal muscle along its fiber direction.
Although we preserved the outer longitudinal muscle layer during POEM, we assumed that inflammation would extend beyond the esophageal adventitia, thereby resulting in strong adhesion formation between the surrounding tissues. However, fibrous formation around the esophagus (including the pericardial surface) was not as intense as expected; therefore, the exfoliation of the esophagus from the surrounding tissues was relatively easy. In general, some minor mediastinal emphysema may occur immediately after POEM . Except for the rare cases of mediastinitis due to post-POEM mucosal injury , POEM has little impact outside of the esophageal adventitia.