In Japan EGC is the commonest malignancy, in consequence of the nation-wide screening system in the country. In the West also there is a trend for EGC to increase as a proportion of all resected gastric cancers, because of improvement of diagnostic techniques
( Sano).
Everett and Axon affirm that the clinicopathological features of the disease are remarkably similar between Japan and the West (Everett).
In the countries with a high prevalence of the disease like Japan a mass screening is in use. In the West the early detection of gastric cancer comes from a selective screening of symptomatic patients.
Many EGC patients present with symptoms of benign gastric ulcer. Therefore patients with ulcer symptoms should undergo endoscopy with biopsy at least once after the symptoms are relieved by medication.
A prospective study demonstrated that EGC progresses to advanced cancer in a median period of 37 months. For this reason it is recommended to submit patients with recurrent ulcer symptoms to endoscopy
(Sano).
Only the histological confirmation of the depth of tumor invasion gives the final diagnosis, but pretreatment diagnosis of the disease is essential today.
For endoscopists who have never diagnosed EGC it may be easy overlook it. Japanese endoscopists distinguish EGC from deeper tumors in 90% of patients by routine endoscopy alone, examining the color and stiffness of the lesion and the shape of converging folds, while they adjust the volume of the air in the stomach.
The lack of experience of Western endoscopist, who have not many occasions to diagnose EGC influence the surgical strategy of Western surgeons, but we will discuss this object in the forthcoming article in Surgical Oncology net
(Sano).
Between 1972 and 1982 the percentage of early gastric cancer less than 2.0 cm in size rose from 30% to 40% in Japan. And among all gastric cancers detected, the percentage of small gastric cancers less than 1.0 cm in size rose from 9,7% to 14,3% between 1972 and 1982. Moreover In recent years the percentage of early gastric cancers, among all surgically treated gastric cancers, has risen to about 60%.
Therefore it is important to improve the detection of small lesions with endoscopy, in particular the detection of microcancers less than 2.0cm in diameter. In particular due to the spread of methods of endoscopic treatment.
Hiki describes a method for measuring lesion size: the disc method. A rubber disc, 5 mm in diameter is held with biopsy forceps and inserted into the stomach. The disc is placed at the center or on the periphery of the lesions and then photographed.
Moreover the author mentions the procedure of dye scattering endoscopy and the types of dyes used in this examination. This is an endoscopic technique in which dye allows endoscopic observation of the morphology and function of the gastric mucosa, that would be impossible or difficult to study by conventional endoscopy. There is also a method for increasing the diagnostic accuracy in the color of the vasoconstriction by the spraying of a drug that acts directly on the capillaries in the gastric mucosa (Hiki).
Yanai let us know that there are a few reports on the relation between the tumour invasion depth staging characteristics of endoscopy and EUS.
Endoscopists can perform target scanning with high resolution of even very small gastric cancer lesions under endoscopic control thanks to the recent introduction of high frequency thin endoscopic ultrasound probes.
Yanai concludes that the overall accuracy rates for staging depth of invasion for endoscopy and EUS are 72,2% and 64,8% respectively. EUS shows a higher overstaging rate. Lesions that are classified as being limited to the mucosa, by both endoscopy and EUS are found to be limited to the mucosa in the percentage of 92,2% on histological examination.
EUS compensates for the understaging of lesions with submucosal invasion that are endoscopically staged as mucosal cancer (Yanai).
Ohashi refers a EUS accuracy of assessing the depth of invasion of over 90%. In his study patients showing no changes in the submucosal layer or deeper on EUS include patients with mucosal cancer (80%) and those with submucosal cancer having a very slight infiltration into the submucosa (20%) pathologically.
With regard to lymph nodes the specifity of identification of nodes involved is greater than 80%.
Threrefore EUS assessment is essential before deciding for the endoscopic treatment.
It is obvious that only after endoscopic resection has been performed , the lesion may be classified as intramucosal or submucosal by examination of the specimen.
Moreover EUS and endoscopy are effective in clarifying changes both within and between anatomic levels during follow up ( Ohashi).
It is described in the literature another ultrasound technique, the percutaneous abdominal ultrasound with hydrotechnique. The tumors of the corpus and antrum can be adequately visualized by hydrosonography, the region of the cardia is more difficult to investigate. The accuracy rate for the T category is 42% and for the n category 66%, if the tumor is at all detectable by hydrosonography. However small gastric cancers pT1,pT2 can be better differentiate with the high resolution capacity of EUS (12 MHz) than with hydrosonography
( Kuntz ).
With regard to lymph nodes metastasis the diagnostic sensitivity in patients with early gastric cancer is very low by preoperative CT,US, EUS and by intraoperative assessment. In fact metastatic lymph nodes are quite small and demonstrate only subtle histologic changes.
When the metastatic area occupy > 10% of the whole area of the cut surface of the lymph node, pericancerous fibrosis is often observed. For this reason lymph node metastasis can be predicated by a hard consistency but not by the size or the shape of the lymph node.
There are several histologic methods that have increased diagnostic sensitivity, but they are time consuming, expensive and the rate of incidence of this type of metastasis is low. These methods are serial sectioning to detect occult metastasis, evaluating the metastatic mode for the surgical determination of the dissection level, microscopic measurement of the maximum dimension of the lymph node for diagnostic correlation of metastasis by EUS, and immunohistologic staining and molecular biologic techniques for the detection of micrometastasis.
But it is the advent of computer technology that permits to apply image analysis to the exam of lymph node metastasis in patients with early gastric carcinoma. Digital quantitative analysis is more useful and objective than measurements by microscopy and is widely applicable to the clinicopathologic evaluation of lymph nodes (Nakamura).
References
Sano T et al. The management of Early Gastric Cancer. Surgical Oncology 2000; 9: 17-22.
Everett SM et al. Early Gastric Cancer in Europe. Gut 1997; 41: 142-150.
Yoshiki Hiki PhD. Endoscopic diagnosis of mucosal cancer. Semin. Surg. Oncol. 17:91-95,1999.
Yanai H et al. A blind comparison of the effectiveness of endoscopic ultrasonography and endoscopy in staging early gastric cancer. Gut 1999;44: 361-65.
Ohashi A et al. The utility of endoscopic ultrasonography and endoscopy in the endoscopic mucosal resection of early gastric cancer. Gutt 1999;45:599-604.
Kuntz C et al. Imaging diagnosis for staging of gastric cancer. Semin.Surg. Oncol. 17:96-102, 1999.
Nakamura K et al. Morphometric analysis of regional lymph node with and without metastasis from early gastric carcinoma. Cancer 2000; 88: 2438-42.
