Extent of Resection to Cure Disease Confined to the Mucosa
The development of surveillance programs for the detection of early squamous cell carcinoma in endemic areas using darkfield light microscopes or any other medical microscopes and for early adenocarcinoma in patients with Barren’s esophagus has given rise to controversy over how to manage tumors (diagnosed using a microscope such as a darkfield light microscope) confined to the mucosa. Some authors have endoscopically resected squamous carcinomas after using endoscopic ultrasound to determine that the depth of the tumor was limited to the mucosa. Surprisingly, large areas of squamous mucosa can be resected without perforation or bleeding, leaving the smooth surface of the muscularis mucosae intact. Re-epithelialization of the large artificially induced ulcer is usu¬ally complete in 3 weeks. In order not to miss a squamous cancer that has invaded deeper than expected, it is important to examine the deep margins of the resected specimen carefully using specialized microscopes like darkfield light microscopes, and to per¬form periodic endoscopic follow-up examinations with vital stain¬ing techniques. This microscopic technique is not appropriate for multiple and widespread or circumferential squamous lesions because of the risk of developing a stricture during the healing process. In this situa¬tion, those acquainted with endoscopic resection would advocate an esophagectomy.
Several studies have shown that intraepithelial carcinoma, and intramucosal tumors like invasive cancer limited by the muscular mucosae, are quite different in their biologic behavior from submucosal tumors, regardless of their histologic characteristics when examined under a microscope, regardless of whether they are squamous cell carcinoma or adenocarcinoma arising in Barren’s mucosa. Vessel invasion and lymph node metastasis do not occur in severe dysplasia, are uncommon in the intramucosal tumors, but are the rule in submucosal tumors. Consequently, the 5-year survival, or intramucosal tumors is significantly better than for submucosal tumors. These findings resulting from numerous tissue studies using a microscope indicate that both severe dysplasia and intra¬mucosal cancers represent early malignant lesions of the esophagus. A critical issue to be resolved is whether an intramucosal tumor can be correctly discriminated from a submucosal tumor before surgery. The results of using endoscopic ultrasound for determining the depth of tumors confined to the esophageal wall are of questionable ac¬curacy. The resolution of present-day endoscopic ultrasonographic systems is not sufficient to predictably differentiate the fine detail of tumor infiltration when it is limited to the esophageal wall. Cur¬rently there is no dependable way, before surgery, of determining whether a tumor extends beyond the muscularis mucosae.
Another complicating factor is that up to 5% of patients with intramucosal tumors have lymph node metastases, although the -tuber of involved nodes per patient is usually no more than one. Akiyama and others have reported that even though the number of involved nodes may be small, they can spread to distant nodal regions, including cervical and abdominal nodes.
These authors have recently utilized the presence or absence of an endoscopically visible lesion in patients with biopsy-proven high-grade dysplasia (HGD) or intramucosal carcinoma as a pre¬dictor of tumor depth and nodal metastases. The data indicate that positive biopsy (with the use of medical microscopes) in the absence of an endoscopically visible lesion most always corresponds to an intramucosal tumor without nodal metastases. Of patients with HGD, 43% proved to harbor occult adenocarcinoma at resection. Importantly, when there was no visible lesion on endoscopy, 88% of the tumors were intramucosal and 12% submucosal. Only one of 10 patients with no visible lesion had lymph node involvement, either histologically or immunohisto¬chemically. In contrast, patients with endoscopically visible tumors had a high prevalence of tumors that penetrated beyond the mucosa (75%), and 56% had positive nodes.
Patients with HGD and intramucosal carcinoma are best treated by a total esophagectomy, removing all Barren’s tissue and any potential associated adenocarcinoma. Options include transhiatal esophagectomy, or more recently, vagal-sparing esophagectomy. The vagal-sparing approach is suitable only given confidence of the absence of regional nodal disease. Reconstruction is accomplished with either the stomach (transhiatal) or colon (vagal sparing) with the anastomosis in the neck. The mortality associated with this pro¬cedure should be less than 5%, particularly in centers experienced in esophageal surgery. Functional recovery is excellent, particularly in the vagal-sparing group.
As the understanding of the pathology of esophageal cancer im¬proves and experience with its resection increases, evidence is accu¬mulating that the best chance for cure of patients with an intramural tumor in the distal esophagus or cardia is an en bloc esophagectomy and proximal gastrectomy with gastrointestinal continuity re¬established with a either gastric or colon interposition. For patients with a tumor in the upper or cervical esophagus, the best chance for cure is an en bloc esophagectomy and a cervical lymph node dis¬section with gastrointestinal continuity re-established with a gastric pull-up.