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Page 2 of 9 Ishihara. Mini-invasive Surg 2021;5:36 https://dx.doi.org/10.20517/2574-1225.2021.72

INTRODUCTION
Esophageal cancer is the seventh most common cancer and the sixth most common cause of cancer-related
[1]
death worldwide, with 572,000 new cases and 509,000 deaths in 2018 . Although the incidence of
esophageal adenocarcinoma is increasing rapidly in Europe and North America, esophageal squamous cell
carcinoma (SCC) remains the most common histological type, accounting for 80% of all esophageal cancers
[1]
worldwide .
The overall survival of patients with advanced esophageal cancer remains poor, regardless of histological
type. However, when diagnosed at an early stage, esophageal cancer can be cured by endoscopic submucosal
dissection (ESD), surgical resection, or chemoradiotherapy. Superficial SCC is defined as cancer limited to
the mucosa or the submucosa. The treatment strategy for superficial SCC of the esophagus is determined
based on the preoperative diagnosis of cancer invasion depth, lateral extent of the cancer, and metastasis.
The curative ability of tumor resection is usually determined by the histologic findings of the resected
specimen. This review will discuss the preferred preoperative examinations, indications for ESD, and
curative ability of ESD in patients with esophageal SCC.

PREOPERATIVE EXAMINATIONS
Diagnosis of cancer invasion depth
Endoscopic evaluation by non-magnifying endoscopy (non-ME) followed by magnifying endoscopy (ME)
is the common procedure for diagnosing invasion depth of superficial esophageal SCC in Japan. Endoscopic
ultrasonography (EUS) is also used to diagnose cancer invasion depth but is currently not used as a
[2,3]
standard procedure because of conflicting results regarding its diagnostic accuracy . Although EUS is
[7]
recommended for staging T1 esophageal cancer in some guidelines and by some experts , it is not
[4-6]
recommended in other guidelines . A recent multicenter study was conducted to evaluate the additional
[8,9]
diagnostic value of EUS following non-ME+ME for differentiating superficial SCC into M/SM1 cancer
(mucosal cancer/cancer invading into the submucosa by ≤ 200 µm) and ≥ SM2 cancer (cancer invading into
[10]
the submucosa > 200 µm) . Additional use of EUS after non-ME+ME increased the proportion of
overdiagnoses by 6.6% (21.6% vs. 28.2%, one-sided P = 0.93), with similarly increased tendencies for
overdiagnosis in all subgroup analyses. Although the addition of EUS reduced the proportion of
underdiagnoses by 4.5% (29.2% vs. 24.7%), it did not improve the accuracy of distinguishing between
M/SM1 and ≥ SM2 superficial SCCs. Overdiagnosis of the depth of invasion means that cancers potentially
curable by endoscopic resection may be treated by esophagectomy, while underdiagnosed cancers may be
treated by endoscopic resection, with no curative effect. An increase in overdiagnosis is considered to have a
greater impact than underdiagnosis, because over diagnosed patients may receive unnecessary
esophagectomy, which is more invasive than unnecessary endoscopic resection caused by an
underdiagnosis. Similar results were reported in other studies evaluating the usefulness of additional
EUS [11,12] . Considering the risk-benefit balance of adding EUS, the current results suggest that EUS should
not be performed routinely in patients with superficial esophageal SCC.

Diagnosis of lateral extent
The Esophageal Cancer Practice Guidelines 2017 suggest that the extent of endoscopic resection is closely
[4]
related to the risk of stenosis, and it is therefore “strongly recommended to evaluate the circumferential
extent of the lesion preoperatively”. Image-enhanced magnifying endoscopy or iodine staining is
recommended to diagnose the lateral extent of the lesion [Figure 1], with the latter allowing clear
delineation of the lesion border. However, use of high concentrations of iodine solution may cause the
superficial epithelium to peel off, making a subsequent diagnosis difficult, and thus iodine solution should
be used at a low concentration of ≤ 1%.