Digital Assessment of Gingival Dimensions of Healthy Periodontium.

The aim of the present study was to re-visit the gingival dimension using digital scanning in a healthy Korean population. Forty-eight periodontally healthy volunteers (38 males and 10 females, mean age: 24.3 ± 2.2 years) were included. The mucogingival junction was highlighted using 2.5% diluted iodine solution. Then, the facial gingiva and mucosa of both jaws were digitally scanned using an intraoral digital scanner. Using computer software and periodontal probing, the heights and areas of keratinized gingiva (KG) and attached gingiva (AG) were measured. Similar distribution patterns in the gingival heights were noted in the maxilla and mandible. The maxilla showed substantially greater gingival values than the mandible. The heights of the KG and AG were notably smaller on the mandibular first premolar (2.37 mm and 1.07 mm, median value) and second molar (3.28 mm and 1.78 mm) than on the other teeth. The area of the KG was the largest in the canine (63.74 mm2 and 46.85 mm2) and first molar (64.14 mm2 and 58.82 mm2) in each jaw. Mandibular first and second molars, mandibular canine, and maxillary canine showed the highest value of the area under the receiver operation characteristics curve (>0.7) for differentiating between males and females. The gingival dimensions recorded using intraoral scanner demonstrated similar distribution patterns as in previous studies.

Histological comparison of different compressive forces on particulate grafts during alveolar ridge preservation: a prospective proof-of-concept study.

PURPOSE: The aim of this study was to determine the impact of different compressive forces on deproteinized bovine bone mineral (DBBM) particles covered by native bilayer collagen membrane (NBCM) during alveolar ridge preservation (ARP) in the molar area, and to identify any histomorphometric and clinical differences according to the compressive force applied. METHODS: Sockets were filled with DBBM after tooth extraction, and different compressive forces (30 N and 5 N, respectively) were applied to the graft material in the test (30 N) and control (5 N) groups. The DBBM in both groups was covered with NBCM in a double-layered fashion. A crossed horizontal mattress suture (hidden X) was then made. A core biopsy was performed using a trephine bur without flap elevation at the implant placement site for histomorphometric evaluations after 4 months. The change of the marginal bone level was measured using radiography. RESULTS: Twelve patients completed the study. The histomorphometric analysis demonstrated that the mean ratios of the areas of new bone, residual graft material, and soft tissue and the implant stability quotient did not differ significantly between the groups (P>0.05). However, the mean size of the residual graft material showed a significant intergroup difference (P<0.05). CONCLUSIONS: The application of 2 compressive forces (5 N, 30 N) on particulate DBBM grafts during open-healing ARP in the posterior area led to comparable new bone formation, implant feasibility and peri-implant bone level.

A scoring system for the diagnosis of non-alcoholic steatohepatitis from liver biopsy.

BACKGROUND: Liver biopsy is the essential method to diagnose non-alcoholic steatohepatitis (NASH), but histological features of NASH are too subjective to achieve reproducible diagnoses in early stages of disease. We aimed to identify the key histological features of NASH and devise a scoring model for diagnosis. METHODS: Thirteen pathologists blindly assessed 12 histological factors and final histological diagnoses ('not-NASH,' 'borderline,' and 'NASH') of 31 liver biopsies that were diagnosed as non-alcoholic fatty liver disease (NAFLD) or NASH before and after consensus. The main histological parameters to diagnose NASH were selected based on histological diagnoses and the diagnostic accuracy and agreement of 12 scoring models were compared for final diagnosis and the NAFLD Activity Score (NAS) system. RESULTS: Inter-observer agreement of final diagnosis was fair (κ = 0.25) before consensus and slightly improved after consensus (κ = 0.33). Steatosis at more than 5% was the essential parameter for diagnosis. Major diagnostic factors for diagnosis were fibrosis except 1C grade and presence of ballooned cells. Minor diagnostic factors were lobular inflammation ( ≥ 2 foci/ × 200 field), microgranuloma, and glycogenated nuclei. All 12 models showed higher inter-observer agreement rates than NAS and post-consensus diagnosis (κ = 0.52-0.69 vs. 0.33). Considering the reproducibility of factors and practicability of the model, summation of the scores of major (× 2) and minor factors may be used for the practical diagnosis of NASH. CONCLUSIONS: A scoring system for the diagnosis of NAFLD would be helpful as guidelines for pathologists and clinicians by improving the reproducibility of histological diagnosis of NAFLD.

Early implant failure: a retrospective analysis of contributing factors.

PURPOSE: The aim of this retrospective study was to determine the prevalence of early implant failure using a single implant system and to identify the factors contributing to early implant failure. METHODS: Patients who received implant treatment with a single implant system (Luna®, Shinhung, Seoul, Korea) at Dankook University Dental Hospital from 2015 to 2017 were enrolled. The following data were collected for analysis: sex and age of the patient, seniority of the surgeon, diameter and length of the implant, position in the dental arch, access approach for sinus-floor elevation, and type of guided bone regeneration (GBR) procedure. The effect of each predictor was evaluated using the crude hazard ratio and the adjusted hazard ratio (aHR) in univariate and multivariate Cox regression analyses, respectively. RESULTS: This study analyzed 1,031 implants in 409 patients, who comprised 169 females and 240 males with a median age of 54 years (interquartile range [IQR], 47-61 years) and were followed up for a median of 7.2 months (IQR, 5.6-9.9 months) after implant placement. Thirty-five implants were removed prior to final prosthesis delivery, and the cumulative survival rate in the early phase at the implant level was 95.6%. Multivariate regression analysis revealed that seniority of the surgeon (residents: aHR=2.86; 95% confidence interval [CI], 1.37-5.94) and the jaw in which the implant was placed (mandible: aHR=2.31; 95% CI, 1.12-4.76) exerted statistically significant effects on early implant failure after adjusting for sex, age, dimensions of the implant, and type of GBR procedure (preoperative and/or simultaneous) (P<0.05). CONCLUSIONS: Prospective studies are warranted to further elucidate the factors contributing to early implant failure. In the meantime, surgeons should receive appropriate training and carefully select the bone bed in order to minimize the risk of early implant failure.

Reverse-transcription loop-mediated isothermal amplification (RT-LAMP) assay for the visual detection of European and North American porcine reproductive and respiratory syndrome viruses.

A reverse transcription loop-mediated isothermal amplification (RT-LAMP) assay for visual detection of European (EU) and North American (NA) porcine reproductive and respiratory syndrome viruses (PRRSVs) were established and evaluated with reference PRRSV strains and clinical samples. The assay was performed in two reaction tubes containing each set of primers specific for EU or NA-PRRSV at 58°C for 40min, and the results could be visually detected by the naked eye, using hydroxynaphthol blue dye. The detection limit of the assay was 1 or 0.1 TCID50/0.1mL for EU or NA PRRSV, respectively, which was comparable to that of the previously described real-time RT-PCR (qRT-PCR). The detection rate of the assay on 130 field samples was 72.3%, relatively higher than that of qRT-PCR (70.8%), and there was high overall percentage agreement between the two assays. The high specificity, sensitivity, and reliability of the RT-LAMP assay described in this study renders it useful for the rapid and differential diagnosis of EU and NA PRRSVs, even in under-equipped laboratories.

Interobserver Agreement on Pathologic Features of Liver Biopsy Tissue in Patients with Nonalcoholic Fatty Liver Disease.

BACKGROUND: The histomorphologic criteria for the pathological features of liver tissue from patients with non-alcoholic fatty liver disease (NAFLD) remain subjective, causing confusion among pathologists and clinicians. In this report, we studied interobserver agreement of NAFLD pathologic features and analyzed causes of disagreement. METHODS: Thirty-one cases of clinicopathologically diagnosed NAFLD from 10 hospitals were selected. One hematoxylin and eosin and one Masson's trichrome-stained virtual slide from each case were blindly reviewed with regard to 12 histological parameters by 13 pathologists in a gastrointestinal study group of the Korean Society of Pathologists. After the first review, we analyzed the causes of disagreement and defined detailed morphological criteria. The glass slides from each case were reviewed a second time after a consensus meeting. The degree of interobserver agreement was determined by multi-rater kappa statistics. RESULTS: Kappa values of the first review ranged from 0.0091-0.7618. Acidophilic bodies (k = 0.7618) and portal inflammation (k = 0.5914) showed high levels of agreement, whereas microgranuloma (k = 0.0984) and microvesicular fatty change (k = 0.0091) showed low levels of agreement. After the second review, the kappa values of the four major pathological features increased from 0.3830 to 0.5638 for steatosis grade, from 0.1398 to 0.2815 for lobular inflammation, from 0.1923 to 0.3362 for ballooning degeneration, and from 0.3303 to 0.4664 for fibrosis. CONCLUSIONS: More detailed histomorphological criteria must be defined for correct diagnosis and high interobserver agreement of NAFLD.

Clear cell carcinoid of the appendix: Report of two cases with literature review.

The clear cell/lipid-rich change has been described in neuroendocine tumors in several organs, but rarely observed in the appendix. In this study, we describe the morphologic, immunohistochemical features of incidentally discovered appendiceal carcinoids entirely represented by clear cells in a 22-year-old man and a 52-year-old woman. Ultrastructual examination demonstrated abundant lipid droplets and dense core granules. The mechanism leading to lipid accumulation in the cytoplasm has not been discovered, but degenerative processes following recurrent inflammatory change might be considered. This uncommon variant of appendiceal classic carcinoid tumors may bear a superficial resemblance to goblet carcinoid and/or appendiceal metastases from clear cell carcinoma. Awareness of clear cell carcinoid of the appendix will prevent incorrect diagnosis and unnecessary aggressive management.

TisN0M1 Sigmoid Colon Cancer: A Case Report.

Distant metastasis of a colon carcinoma in situ has not yet been reported. We experienced a case of a sigmoid colon carcinoma in situ with common hepatic lymph node metastasis. After the first operation, we diagnosed dual intramucosal adenocarcinomas of the sigmoid colon without any regional lymph node metastasis. After the second operation, a metastatic adenocarcinoma was found in the common hepatic lymph nodes. We suggest that metastasis in cases of a colonic carcinoma in situ is rare, but possible. The parallel progression model of tumors can explain this early metastasis.

Inhibitory effects of rapamycin on the different stages of hepatic fibrosis.

AIM: To investigate and compare the inhibitory effects of rapamycin in the different stages of liver fibrosis. METHODS: We performed bile duct ligation (BDL) in male Wistar rats (n = 24). The experimental rats were classified into four groups: the BDL(+)/Rapa(-) group (un-treated control, n = 4), the BDL(+)/Rapa(+) group (treated 14 d after BDL, n = 8), the BDL(+)/Rapa(++) group (treated on the day after BDL, n = 8), and the BDL(-)/Rapa(-) group (un-treated, sham -operated control, n = 4). The BDL(+)/Rapa(+) and BDL(+)/Rapa(++) groups were administered rapamycin (2 mg/kg) for 28 d. The liver tissues were tested by immunohistochemical staining for α-smooth muscle actin (α-SMA) and cytokeratin. RESULTS: The liver mRNA levels of transforming growth factor (TGF)-ß1 and platelet-derived growth factor (PDGF) were measured using the polymerase chain reaction. The protein levels of liver p70s6K and p-p70s6k were determined using Western blotting. α-SMA expression was lowest in the BDL(+)/Rapa(++)group. TGF-ß1 and PDGF expression levels in the rapamycin-treated group were lower than those in the un-treated group and higher than those in the control groups (TGF-ß1: 0.23 ± 0.00 vs 0.34 ± 0.01, 0.23 ± 0.0 vs 0.09 ± 0.00, P < 0.0001; PDGF: 0.21 ± 0.00 vs 0.34 ± 0.01, 0.21 ± 0.0 vs 0.09 ± 0.00, P < 0.0001). The p70s6k and p-p70s6k levels decreased in the treated groups and were lowest in the BDL(+)/Rapa(++)group (p70s6k: 1.05 ± 0.17 vs 1.30 ± 0.56, 0.40 ± 0.01 vs 1.30 ± 0.56, P < 0.0001; p-p70s6k: 1.40 ± 0.5 vs 1.67 ± 0.12, 0.70 ± 0.01 vs 1.67 ± 0.12, P < 0.0001). CONCLUSION: The results of our study indicate that rapamycin has inhibitory effects on liver fibrosis, and the treatment is most effective in the early stages of fibrosis.

Prognostic significance of p53, mTOR, c-Met, IGF-1R, and HSP70 overexpression after the resection of hepatocellular carcinoma.

BACKGROUND/AIMS: The current study examines the expression of molecular biomarkers in hepatocellular carcinoma (HCC) and whether these findings correlate with the clinicopathologic features of the disease and patient survival. METHODS: We analyzed the immunohistochemical expression of p53, mammalian target of rapamycin (mTOR), c-Met, and insulin-like growth factor 1 receptor (IGF-1R) heat shock protein 70 (HSP70) with the clinicopathologic features of 83 HCCs. RESULTS: p53 expression was higher in the male patients with undifferentiated histological tumor grades, cirrhosis, and portal vein invasion. High 48 c-Met expression correlated with cirrhosis, and high mTOR expression correlated with the tumor grade and cirrhosis. High IGF-1R expression correlated with the tumor grade and cirrhosis. A multivariate analysis identified a significant relationship between the high expression of p53, tumor grade, and portal vein invasion. In addition, a high expression of mTOR was related to tumor grade and cirrhosis, and a high expression of HSP70 was related to portal vein invasion in a multivariate analysis. The Kaplan-Meier survival curve for patients with high versus low Edmondson grades and p53 expression was statistically significant. CONCLUSIONS: p53, mTOR, and IGF-1R expression correlated with the Edmondson tumor grade in a univariate analysis, while p53 and mTOR correlated with the Edmondson tumor grade in a multivariate analysis. In addition, the tumor grade was found to predict survival. p53 was primarily related to the clinicopathologic features compared to other markers, and it is a poor prognostic factor of survival.

A case of liver fibrosis with splenomegaly after oxaliplatin-based adjuvant chemotherapy for colon cancer.

Previous studies reported that oxaliplatin is associated with sinusoidal obstruction syndrome. However few reports on oxaliplatin induced liver fibrosis are found in the literature. Furthermore pathogenesis of liver fibrosis is not well known. We report a case of 45-yr-old Korean man in whom liver fibrosis with splenomegaly developed after 12 cycles of oxaliplatin based adjuvant chemotherapy for colon cancer (T4N2M0). Thorough history taking and serological examination revealed no evidence of chronic liver disease. Restaging CT scans demonstrated a good response to chemotherapy. Five month after chemotherapy, he underwent right hepatectomy due to isolated metastatic lesion. The liver parenchyma showed diffuse sinusoidal dilatation and centrilobular vein fibrosis with necrosis without steatosis. We could conclude that splenomegaly was due to perisinusoidal liver fibrosis and liver cell necrosis induced portal hypertension by oxaliplatin. In addition, to investigate the pathogenesis of liver fibrosis, immunohistochemical stains such as CD31 and α-smooth muscle actin (α-SMA) were conducted with control group. The immunohistochemical stains for CD31 and α-SMA were positive along the sinusoidal space in the patient, while negative in the control group. Chemotherapy with oxaliplatin induces liver fibrosis which should be kept in mind as a serious complication.

A Phase II Study of Additional Four-Week Chemotherapy With Capecitabine During the Resting Periods After Six-Week Neoadjuvant Chemoradiotherapy in Patients With Locally Advanced Rectal Cancer.

PURPOSE: The aim of this study is to evaluate the efficacy and the safety of additional 4-week chemotherapy with capecitabine during the resting periods after a 6-week neoadjuvant chemoradiotherapy (NCRT) in patients with locally advanced rectal cancer. METHODS: Radiotherapy was delivered to the whole pelvis at a total dose of 50.4 Gy for 6 weeks. Oral capecitabine was administered at a dose of 825 mg/m(2) twice daily for 10 weeks. Surgery was performed 2-4 weeks following the completion of chemotherapy. RESULTS: Between January 2010 and September 2011, 44 patients were enrolled. Forty-three patients underwent surgery, and 41 patients completed the scheduled treatment. Pathologic complete remission (pCR) was noted in 9 patients (20.9%). T down-staging and N down-staging were observed in 32 patients (74.4%) and 33 patients (76.7%), respectively. Grade 3 to 5 toxicity was noted in 5 patients (11.4%). The pCR rate was similar with the pCR rates obtained after conventional NCRT at our institute and at other institutes. CONCLUSION: This study showed that additional 4-week chemotherapy with capecitabine during the resting periods after 6-week NCRT was safe, but it was no more effective than conventional NCRT.

Proposal for a standardized pathology report of gastroenteropancreatic neuroendocrine tumors: prognostic significance of pathological parameters.

BACKGROUND: There is confusion in the diagnosis and biological behaviors of gastroenteropancreatic neuroendocrine tumors (GEP-NETs), because of independently proposed nomenclatures and classifications. A standardized form of pathology report is required for the proper management of patients. METHODS: We discussed the proper pathological evaluation of GEP-NET at the consensus conference of the subcommittee meeting for the Gastrointestinal Pathology Study Group of the Korean Society of Pathologists. We then verified the prognostic significance of pathological parameters from our previous nationwide collection of pathological data from 28 hospitals in Korea to determine the essential data set for a pathology report. RESULTS: Histological classification, grading (mitosis and/or Ki-67 labeling index), T staging (extent, size), lymph node metastasis, and lymphovascular and perineural invasion were significant prognostic factors and essential for the pathology report of GEP-NET, while immunostaining such as synaptophysin and chromogranin may be optional. Furthermore, the staging system, either that of the 2010 American Joint Cancer Committee (AJCC) or the European Neuroendocrine Tumor Society (ENETS), should be specified, especially for pancreatic neuroendocrine neoplasms. CONCLUSIONS: A standardized pathology report is crucial for the proper management and prediction of prognosis of patients with GEP-NET.

A case of primary adenosquamous carcinoma of the liver.

Adenosquamous carcinoma (ASC) is a rare tumor of the liver, which carries a poor prognosis. It has been reported mostly in the form of case studies. Recently, we experienced a case of primary ASC of the liver that has been preoperatively considered as cholangiocelluar carcinoma of the liver. Microscopically, the tumor was composed of adenocarcinoma, squamous cell carcinoma, as well as transitional area, including the transformation of adenocarcinoma to squamous cell carcinoma. The patient remained well with no evidence of post-resection complication or recurrence for 15 month.

Current Trends of the Incidence and Pathological Diagnosis of Gastroenteropancreatic Neuroendocrine Tumors (GEP-NETs) in Korea 2000-2009: Multicenter Study.

PURPOSE: As a result of various independently proposed nomenclatures and classifications, there is confusion in the diagnosis and prediction of biological behavior of gastroenteropancreatic neuroendocrine tumors (GEP-NETs). A comprehensive nationwide study is needed in order to understand the biological characteristics of GEP-NETs in Korea. MATERIALS AND METHODS: We collected 4,951 pathology reports from 29 hospitals in Korea between 2000 and 2009. Kaplan-Meier survival analysis was used to determine the prognostic significance of clinicopathological parameters. RESULTS: Although the GEP-NET is a relatively rare tumor in Korea, its incidence has increased during the last decade, with the most significant increase found in the rectum. The 10-year survival rate for well-differentiated endocrine tumor was 92.89%, in contrast to 85.74% in well differentiated neuroendocrine carcinoma and 34.59% in poorly differentiated neuroendocrine carcinoma. Disease related death was most common in the biliary tract (62.2%) and very rare in the rectum (5.2%). In Kaplan-Meier survival analysis, tumor location, histological classification, extent, size, mitosis, Ki-67 labeling index, synaptophysin expression, lymphovascular invasion, perineural invasion, and lymph node metastasis showed prognostic significance (p<0.05), however, chromogranin expression did not (p=0.148). The 2000 and 2010 World Health Organization (WHO) classification proposals were useful for prediction of the prognosis of GEP-NET. CONCLUSION: The incidence of GEP-NET in Korea has shown a remarkable increase during the last decade, however, the distribution of tumors in the digestive system differs from that of western reports. Assessment of pathological parameters, including immunostaining, is crucial in understanding biological behavior of the tumor as well as predicting prognosis of patients with GEP-NET.

Use of covered stents in the central vein: a feasibility study in a canine model.

PURPOSE: To evaluate the feasibility of using covered stents vs. bare stents in a model of central vein stenosis with an arteriovenous graft created to mimic the conditions in hemodialysis patients. METHODS: In 7 mongrel dogs, an expanded polytetrafluoroethylene-covered nitinol stent was placed in one common iliac vein and a bare stent was placed in the contralateral vein. Arteriovenous grafts were created bilaterally between the common femoral artery and vein to induce endothelial damage. Neointima formation in the covered stents was compared to the bare stents at 12 weeks using microscopy and histochemical staining. RESULTS: Two dogs were excluded due to thrombosis and infection of the arteriovenous grafts, but all stents in the remaining 5 dogs were patent. Smooth, complete neointimal coverage was observed on the inner surface of all the covered stents without intraluminal thrombus. In contrast, incomplete neointimal coverage was seen in all bare stents, with small focal thrombi adhering to the neointima on 3 bare stents. Focal nodular neointimal hyperplasia with denudation of the endothelium was observed in only 2 bare stents. Mean neointimal thickening was significantly greater in the covered stents. Eccentric neointimal thickening was observed at the inflow and outflow segments of both types of stents. CONCLUSION: Covered stents are technically feasible for the treatment of central vein stenosis, and they demonstrate complete, smooth neointimal coverage in normal central veins, but they also display greater neointimal thickening than bare stents.

Recurrent renal leiomyosarcoma mimicking a colonic submucosal tumor: a case report.

A primary leiomyosarcoma of the kidney is a rare, but highly aggressive, neoplasm, accounting for only 0.1% of all invasive renal tumors. Local or systemic recurrence is common, but a leiomyosarcoma is difficult to diagnose preoperatively. We recently encountered an interesting case of an unusual recurrence of a renal leiomyosarcoma. A 57-year-old woman visited our hospital complaining of lower abdominal pain. Four years previously, she had undergone a left nephrectomy. She had a primary leiomyosarcoma of the kidney that had been misdiagnosed as a renal cell carcinoma. Colonoscopy revealed the presence of a lesion similar to a submucosal tumor in the descending colon. Postoperative pathologic examination confirmed that the mass was a recurrent leiomyosarcoma. We report this unusual case and present a review of the literature.

Expression of DOG1, PDGFRA, and p16 in Gastrointestinal Stromal Tumors.

BACKGROUND/AIMS: The diagnosis of gastrointestinal stromal tumors (GIST) relies on the demonstration of KIT expression, but KIT expression is absent or reduced in approximately 15% of GIST. METHODS: Eighty-one GISTs were diagnosed between January 1998 and December 2007 at the Department of Pathology at both Chungnam National University Hospital and Eulji University Hospital, Daejeon. Medical history, patient follow-up, and radiographic data were collected if available in the medical records. To determine diagnostic and prognostic markers for GISTs focused on PDGFRA mutation and clinicopathologic features, we analyzed 81 GIST cases for KIT, PDGFRA, DOG1, and p16 expression and for mutation of PDGFRA genes. RESULTS: Among 81 GIST cases, 20 high risk cases (24.7%) were recurred or metastasized. Immunohistochemically, KIT was positive in 76 (93.8%), PDGFRA in 75 (92.7%), and DOG1 in 77 (95.1%). With a cutoff value of 50%, p16 expression was positive in 26 cases were positive (32.1%). A correlation between p16 expression or negative DOG1 expression and recurrence or metastasis was demonstrated (p<0.05). Four cases showed a missense mutation in exon 12 of PDGFRA gene, three of these were of epithelioid GISTs. Two cases showed a silent mutation in exon 18 of PDGFRA. CONCLUSIONS: These results indicate that the expression of DOG1 and PDGFRA is observed in a majority of GIST cases. Expression of p16 and negative DOG1 expression is predictive for development of recurrence and/or metastasis. Even though mutation of the PDGFRA gene is frequently seen in epithelioid GISTs, a clinicopathologic correlation was not demonstrated.

Diagnosis of gastric epithelial neoplasia: Dilemma for Korean pathologists.

The histopathological diagnosis of gastric mucosal biopsy and endoscopic mucosal resection/endoscopic submucosal dissection specimens is important, but the diagnostic criteria, terminology, and grading system are not the same in the East and West. A structurally invasive focus is necessary to diagnose carcinoma for most Western pathologists, but Japanese pathologists make a diagnosis of cancer based on severe dysplastic cytologic atypia irrespective of the presence of invasion. Although the Vienna classification was introduced to reduce diagnostic discrepancies, it has been difficult to adopt due to different concepts for gastric epithelial neoplastic lesions. Korean pathologists experience much difficulty making a diagnosis because we are influenced by Japanese pathologists as well as Western medicine. Japan is geographically close to Korea, and academic exchanges are active. Additionally, Korean doctors are familiar with Western style medical terminology. As a result, the terminology, definitions, and diagnostic criteria for gastric intraepithelial neoplasia are very heterogeneous in Korea. To solve this problem, the Gastrointestinal Pathology Study Group of the Korean Society of Pathologists has made an effort and has suggested guidelines for differential diagnosis: (1) a diagnosis of carcinoma is based on invasion; (2) the most important characteristic of low grade dysplasia is the architectural pattern such as regular distribution of crypts without severe branching, budding, or marked glandular crowding; (3) if nuclear pseudostratification occupies more than the basal half of the cryptal cells in three or more adjacent crypts, the lesion is considered high grade dysplasia; (4) if severe cytologic atypia is present, careful inspection for invasive foci is necessary, because the risk for invasion is very high; and (5) other structural or nuclear atypia should be evaluated to make a final decision such as cribriform pattern, papillae, ridges, vesicular nuclei, high nuclear/cytoplasmic ratio, loss of nuclear polarity, thick and irregular nuclear membrane, and nucleoli.