Helicobacter pylori is undetectable in intraductal papillary mucinous neoplasm.

BACKGROUND: About half of the world population is infected with Helicobacter pylori (H. pylori), a bacterium associated with gastric cancer and considered to be a risk factor for pancreatic ductal adenocarcinoma. Whether the bacterium is associated with intraductal papillary mucinous neoplasm, believed to be a precursor of pancreatic ductal adenocarcinoma, is unknown. The aim of this study was to investigate the presence of H. pylori DNA in tissue sections of intraductal papillary mucinous neoplasm. METHODS: The presence of H. pylori DNA was tested in a retrospective controlled study of formalin-fixed, paraffin-embedded pancreatic tissues from 24 patients who underwent surgery for intraductal papillary mucinous neoplasm. Histologically normal tissues surrounding neoplasms were used as control. H. pylori DNA was evaluated after deparaffinization, DNA extraction, and purification, and results were evaluated statistically. RESULTS: Samples were collected from 13 males and 11 females with mean age 59 years (range 44-77), and consisted of 19 cases of main-duct and three cases of branched-duct intraductal papillary mucinous neoplasm. Two patients were diagnosed with pancreatic cancer and main-duct intraductal papillary mucinous neoplasm. H. pylori DNA was not detected either in intraductal papillary mucinous neoplasm tissue, or in surrounding normal tissue. CONCLUSIONS: Although H. pylori has been implicated in pancreatic ductal adenocarcinoma, it may not play a key role in the development of intraductal papillary mucinous neoplasm.

The relationship between diverticula and low-grade mucinous neoplasm of the appendix. Does the diverticulum play a role in the development of periappendicular mucin deposition or pseudomyxoma peritonei?

Prevalences of diverticulum and low-grade mucinous neoplasm (LGMN) were reported as 0.04-2% and less than 1% in the appendix. In this study, the frequency of diverticulum in LGMN cases, the relationship between diverticula and periappendicular mucin, and the possible role of diverticula in pseudomyxoma peritonei pathogenesis were researched. Through systematic review and targeted search, 38 LGMN and 96 diverticula were identified, frequencies and relationship between diverticulum and LGMN were analysed. Diverticulum and LGMN were determined in 4.8% and 1.04%, respectively, of 1922 appendectomy materials specifically grossed by the same pathologist. The prevalence of diverticulum was higher in our study than literature. The difference may be due to detailed macroscopic examination. Diverticulum was detected in 60% of LGMN cases. The rate of diverticulum was found to be significantly higher in LGMNs than non-neoplastic diverticulum (p < 0.001). Periappendicular mucin deposition was significantly more frequent in LGMN cases with diverticulum than in other groups (p < 0.05). Follow-ups were available in 18 patients; none of them had mucin deposition in the peritoneal cavity. We detected that periappendicular mucin was highly associated with diverticula in LGMN cases. Periappendicular acellular mucin deposition may not give rise to pseudomyxoma peritonei. We may think that mucin could move out of the appendix through the diverticulum rather than neoplastic spread in some of these cases.

Colonic mucosal pseudolipomatosis: Are we aware of it?

OBJECTIVE: Colonic mucosal pseudolipomatosis is rare, and its pathogenesis is controversial. A number of mechanisms, including mechanical injury during an endoscopic procedure or chemical injury by disinfectant, seem to contribute to its pathogenesis. MATERIAL AND METHODS: This retrospective study examined the colonic biopsies of 1370 patients. These biopsies were preserved at the Department of Pathology of Istanbul Training and Research Hospital between January 2012 and June 2013. RESULTS: We found pseudolipomatosis in 14 of 1370 colonoscopy cases (1.02%). Of these 14 patients, 8 were male and 6 were female. The male patients were between 24 and 66 years, with a mean of 39; the female patients were between 26 and 58 years, with a mean of 42. CONCLUSION: Many endoscopists are unaware of the lesion, and the diagnosis is generally possible only after pathological assessment of multiple biopsies taken from suspect lesions. Here we report and discuss colonic pseudolipomatosis incidentally found in a series of patients undergoing routine colonoscopy, and we underline the endoscopic pattern and diagnostic difficulties.

Calculation of the Ki67 index in pancreatic neuroendocrine tumors: a comparative analysis of four counting methodologies.

Ki67 index is now an essential part of classification of pancreatic neuroendocrine tumors. However, its adaptation into daily practice has been fraught with challenges related to counting methodology. In this study, three reviewers used four counting methodologies to calculate Ki67 index in 68 well-differentiated pancreatic neuroendocrine tumors: (1) 'eye-ball' estimation, which has been advocated as reliable and is widely used; (2) automated counting by image analyzer; (3) manual eye-counting (eye under a microscope without a grid); and (4) manual count of camera-captured/printed image. Pearson's correlation (R) was used to measure pair-wise correlation among three reviewers using all four methodologies. Average level of agreement was calculated using mean of R values. The results showed that: (1) 'eye-balling' was least expensive and fastest (average time <1 min) but had poor reliability and reproducibility. (2) Automated count was the most expensive and least practical with major impact on turnaround time (limited by machine and personnel accessibility), and, more importantly, had inaccuracies in overcounting unwanted material. (3) Manual eye count had no additional cost, averaged 6 min, but proved impractical and poorly reproducible. (4) Camera-captured/printed image was most reliable, had highest reproducibility, but took longer than 'eye-balling'. In conclusion, based on its comparatively low cost/benefit ratio and reproducibility, camera-captured/printed image appears to be the most practical for calculating Ki67 index. Although automated counting is generally advertised as the gold standard for index calculation, in this study it was not as accurate or cost-effective as camera-captured/printed image and was highly operator-dependent. 'Eye-balling' produces highly inaccurate and unreliable results, and is not recommended for routine use.

Comparison of World Health Organization 2000/2004 and World Health Organization 2010 classifications for gastrointestinal and pancreatic neuroendocrine tumors.

Gastroenteropancreatic neuroendocrine tumors (GEPNETs) were divided into 4 groups based on tumor diameter and stage in World Health Organization (WHO) 2000/2004 classification as well-differentiated endocrine tumor benign (WDETB), well-differentiated endocrine tumor with uncertain behavior (WDETUB), well-differentiated endocrine carcinoma (WDEC), and poorly differentiated endocrine carcinoma (PDEC). World Health Organization 2000/2004 was not widely accepted because of stage-related classification and the category of "uncertain behavior." The European NET Society proposed a grading classification and site-specific staging system in 2010. Gastroenteropancreatic NETs were divided into 3 groups as NET grade 1 (G1), NET grade 2 (G2), and neuroendocrine carcinoma (NEC) grade 3 (G3) based on mitoses and the Ki-67 index. We evaluated 63 GEPNET cases according to both classifications. We compared two classifications and the tumor groups in terms of prognostic parameters (diameter, mitosis, Ki-67 index, angioinvasion, perineural invasion, necrosis, and metastasis) and pathologic stage. All 14 cases diagnosed as PDEC were included in the NEC G3 according to WHO 2010. Seventeen cases were diagnosed as WDETB, 9 as WDETUB, and 23 as WDEC. There was statistically significant difference between these groups in terms of all prognostic parameters except for necrosis, mitosis, Ki-67 index, and grade. All WDETB cases, 89% of WDETUBs, and 87% of WDECs were included in the NET G1. There were 45 cases evaluated as NET G1 and 4 cases as NET G2 according to WHO 2010. Metastasis and perineural invasion were more common in NET G2, no significant differences in other parameters. In conclusion, WHO 2010 is easier to use, whereas WHO 2000/2004 shows higher correlation with prognosis. However, it includes benign and uncertain behavior categories, although small tumors with low proliferative activity can also cause metastases. All GEPNETs should be considered potentially malignant.

Assessment of cricopharyngeal muscle aging with apoptotic markers.

OBJECTIVES: The aims of this study were to evaluate histochemical markers of apoptosis in the cricopharyngeus muscle, which is the gatekeeper of the pharyngoesophageal region during the swallowing process; to investigate the effects of primary aging on this muscle; and to determine whether a relationship exists with gastroesophageal reflux disease. MATERIALS AND METHODS: The study included 30 fresh cadavers with a time of death of 12 hours or less obtained from the Turkish Ministry of Justice Forensic Medicine Unit. All cadavers were dissected with routine postmortem skin incisions to extract specimens from the cricopharyngeus muscle and the esophagocardiac junction mucosa. Muscle degeneration and primary aging were demonstrated by immunodetection of Bax, Bcl-2, and Caspase-3 proteins as markers of the apoptosis. Esophageal specimens were examined for the presence of reflux esophagitis. RESULTS: The mean age was 41.5 (14-74) years, and the study included 18 male and 9 female cadavers. Three of them were excluded because of fixation artifacts. The mean Bax, Bcl-2, and Caspase scores showed no statistically significant relationship with age (P = 0.94). The right and left sides of the muscle were investigated separately, and the Bax scores of the right side of the cricopharyngeus muscle showed a statistically significant decrease with age (P = 0.026), whereas the Bax and Bcl-2 scores were increased with age (P = 0.035 and 0.049, respectively) on the left side. Evaluation of the 23 esophagus specimens revealed 10 cases of esophagitis. No relationship was found between the mean of each apoptotic marker and esophagitis. CONCLUSIONS: It is histopathologically not possible to demonstrate muscle death due to either primary aging or reflux. This might be attributable to the defensive capability of this unique muscle to maintain the feeding process.

Correction: Gallbladder polyps: Correlation of size and clinicopathologic characteristics based on updated definitions.

[This corrects the article DOI: 10.1371/journal.pone.0237979.].

Adenomyomas of the Gallbladder: An Analysis of Frequency, Clinicopathologic Associations, and Relationship to Carcinoma of a Malformative Lesion.

CONTEXT.­: The nature and associations of gallbladder (GB) "adenomyoma" (AM) remain controversial. Some studies have attributed up to 26% of GB carcinoma to AMs. OBJECTIVE.­: To examine the true frequency, clinicopathologic characteristics, and neoplastic changes in GB AM. DESIGN.­: Cholecystectomy cohorts analyzed were 1953 consecutive cases, prospectively with specific attention to AM; 2347 consecutive archival cases; 203 totally embedded GBs; 207 GBs with carcinoma; and archival search of institutions for all cases diagnosed as AM. RESULTS.­: Frequency of AM was 9.3% (19 of 203) in totally submitted cases but 3.3% (77 of 2347) in routinely sampled archival tissue. A total of 283 AMs were identified, with a female to male ratio = 1.9 (177:94) and mean size = 1.3 cm (range, 0.3-5.9). Most (96%, 203 of 210) were fundic, with formed nodular trabeculated submucosal thickening, and were difficult to appreciate from the mucosal surface. Four of 257 were multifocal (1.6%), and 3 of 257 (1.2%) were extensive ("adenomyomatosis"). Dilated glands (up to 14 mm), often radially converging to a point in the mucosa, were typical. Muscle was often minimal, confined to the upper segment. Nine of 225 (4%) revealed features of a duplication. No specific associations with inflammation, cholesterolosis, intestinal metaplasia, or thickening of the uninvolved GB wall were identified. Neoplastic change arising in AM was seen in 9.9% (28 of 283). Sixteen of 283 (5.6%) had mural intracholecystic neoplasm; 7 of 283 (2.5%) had flat-type high-grade dysplasia/carcinoma in situ. Thirteen of 283 cases had both AM and invasive carcinoma (4.6%), but in only 5 of 283 (1.8%), carcinoma arose from AM (invasion was confined to AM, and dysplasia was predominantly in AM). CONCLUSIONS.­: AMs have all the features of a malformative developmental lesion, and may not show a significant muscle component (ie, the name "adeno-myoma" is partly a misnomer). While most are innocuous, some pathologies may arise in AMs, including intracholecystic neoplasms, flat-type high-grade dysplasia or carcinoma in situ, and invasive carcinoma (1.8%, 5 of 283). It is recommended that gross examination of GBs include serial slicing of the fundus for AM detection and total submission if one is found.

Extramedullary plasmacytoma of maxillary sinus.

Solitary extramedullary plasmacytomas are rare tumors that often affect the head and neck region. Diagnosis of solitary extramedullary plasmocytoma can be confirmed only when the presence of systemic disease is excluded by performing clinical, biological, and radiological investigations. Radiotherapy is considered the treatment of choice, surgery being limited to biopsy and to excision of residual disease. We report herein the case of a 62-year-old man with an extramedullary plasmacytoma arising in the left maxillary sinus who was referred for chemoradiotherapy.

Radiomics of locally advanced rectal cancer: machine learning-based prediction of response to neoadjuvant chemoradiotherapy using pre-treatment sagittal T2-weighted MRI.

PURPOSE: Variable response to neoadjuvant chemoradiotherapy (nCRT) is observed among individuals with locally advanced rectal cancer (LARC), having a significant impact on patient management. In this work, we aimed to investigate the potential value of machine learning (ML)-based magnetic resonance imaging (MRI) radiomics in predicting therapeutic response to nCRT in patients with LARC. MATERIALS AND METHODS: Seventy-six patients with LARC were included in this retrospective study. Radiomic features were extracted from pre-treatment sagittal T2-weighted MRI images, with 3D segmentation. Dimension reduction was performed with a reliability analysis, pair-wise correlation analysis, analysis of variance, recursive feature elimination, Kruskal-Wallis, and Relief methods. Models were created using four different algorithms. In addition to radiomic models, clinical only and different combined models were developed and compared. The reference standard was tumor regression grade (TRG) based on the Modified Ryan Scheme (TRG 0 vs TRG 1-3). Models were compared based on net reclassification index (NRI). Clinical utility was assessed with decision curve analysis (DCA). RESULTS: Number of features with excellent reliability is 106. The best result was achieved with radiomic only model using eight features. The area under the curve (AUC), accuracy, sensitivity, and specificity for validation were 0.753 (standard deviation [SD], 0.082), 81.1%, 83.8%, and 75.0%; for testing, 0.705 (SD, 0.145), 73.9%, 81.2%, and 57.1%, respectively. Based on the clinical only model as reference, NRI for radiomic only model was the best. DCA also showed better clinical utility for radiomic only model. CONCLUSIONS: ML-based T2-weighted MRI radiomics might have a potential in predicting response to nCRT in patients with LARC.

Reappraisal of T1b gallbladder cancer (GBC): clinicopathologic analysis of 473 in situ and invasive GBCs and critical review of the literature highlights its rarity, and that it has a very good prognosis.

There are highly conflicting data on relative frequency (2-32%), prognosis, and management of pT1b-gallbladder carcinoma (GBC), with 5-year survival ranging from > 90% in East/Chile where cholecystectomy is regarded as curative, versus < 50% in the West, with radical operations post-cholecystectomy being recommended by guidelines. A total of 473 in situ and invasive extensively sampled GBCs from the USA (n = 225) and Chile (n = 248) were re-evaluated histopathologically per Western invasiveness criteria. 349 had invasive carcinoma, and only 24 were pT1. Seven cases previously staged as pT1b were re-classified as pT2. There were 19 cases (5% of all invasive GBCs) qualified as pT1b and most pT1b carcinomas were minute (< 1mm). One patient with extensive pTis at margins (but pT1b focus away from the margins) died of GBC at 27 months, two died of other causes, and the remainder were alive without disease (median follow-up 69.9 months; 5-year disease-specific survival, 92%). In conclusion, careful pathologic analysis of well-sampled cases reveals that only 5% of invasive GBCs are pT1b, with a 5-year disease-specific survival of > 90%, similar to findings in the East. This supports the inclusion of pT1b in the "early GBC" category, as is typically done in high-incidence regions. Pathologic mis-staging of pT2 as pT1 is not uncommon. Cases should not be classified as pT1b unless extensive, preferably total, sampling of the gallbladder to rule out a subtle pT2 is performed. Critical appraisal of the literature reveals that the Western guidelines are based on either SEER or mis-interpretation of stage IB cases as "pT1b." Although the prognosis of pT1b-GBC is very good, additional surgery (radical cholecystectomy) may be indicated, and long-term surveillance of the biliary tract is warranted.

Squamous cell and adenosquamous carcinomas of the gallbladder: clinicopathological analysis of 34 cases identified in 606 carcinomas.

The information in the literature on squamous cell and adenosquamous carcinomas of the gallbladder is highly limited. In this study, 606 resected invasive gallbladder carcinoma cases were analyzed. Squamous differentiation was identified in 41 cases (7%). Those without any identifiable glandular-type invasive component were classified as pure squamous cell carcinomas (8 cases) and those with the squamous component constituting 25-99% of the tumors were classified as adenosquamous carcinomas (26 cases) and included into the analysis. The remaining 7 that had <25% squamous component were classified as adenocarcinoma with focal squamous change and excluded. The clinicopathological characteristics of adenosquamous carcinoma/squamous cell carcinomas were documented and contrasted with that of ordinary gallbladder adenocarcinomas. The average patient age was 65 years (range 26-81); female/male ratio, 3.8. In only 13%, there was a preoperative clinical suspicion of malignancy. Grossly, 58% presented as thickening and hardening of the wall and 6% were polypoid. In 12%, mucosa adjacent to the tumor revealed squamous metaplasia. All pure squamous cell carcinomas had prominent keratinization. Giant cells and tumor-infiltrating eosinophils were observed in 29 and 51% of the squamous cell carcinomas/adenosquamous carcinomas versus 10% (P=0.02) and 6% (P=0.001) in gallbladder adenocarcinomas, respectively. All but three cases had 'advanced' (pT2 and above) carcinomas. Follow-up was available in 31 patients: 25 died of disease (median=5 months, range 0-20), and 6 were alive (median=64 months, range 5-112.5). The survival of patients with squamous cell carcinomas/adenosquamous carcinomas was significantly worse than that of gallbladder adenocarcinomas (P=0.003), and this adverse prognosis persisted when compared with stage-matched advanced gallbladder adenocarcinoma cases (median=11.4 months, P=0.01). In conclusion, squamous differentiation was noted in 7% of gallbladder carcinomas. The incidence of adenosquamous carcinoma (defined as 25-99% of the tumor being squamous) was 4%, and that of pure squamous cell carcinoma (without any documented invasive glandular component) was 1%. Pure squamous cell carcinomas often showed prominent keratinization. The overall prognosis of adenosquamous carcinoma/squamous cell carcinoma appears to be even worse than that of ordinary adenocarcinomas. Most patients died within a few months; however, those few who were alive beyond 2 years in this cohort experienced long-term survival.

[Reliability of ultrasonography for diagnosing acute appendicitis]. / Akut apandisitte ultrasonografinin güvenilirligi.

BACKGROUND: Abdominal ultrasonography (US) is the most commonly used diagnostic tool for diagnosing acute appendicitis, which is one of the most common causes of acute surgical abdomen. In this study, we examined the reliability of US for diagnosing acute appendicitis. METHODS: In this prospective study, we performed abdominal US on 235 patients admitted to our surgical emergency department during 2007 and diagnosed as acute surgical abdomen according to the physical examination and laboratory findings. These patients were surgically treated by appendectomy, and the materials were pathologically examined. RESULTS: Two hundred thirty-five patients were admitted to this study. One hundred ninety-three of these patients (82.1%) were diagnosed as acute appendicitis, and 42 (17.9%) were diagnosed differently. One hundred thirty-three (88.67%) of 150 patients diagnosed as acute appendicitis on US examinations were also reported as acute appendicitis on histopathological examination. Sixty of 85 patients diagnosed differently on US examination were reported as acute appendicitis on histopathological examination. CONCLUSION: The sensitivity of abdominal US for diagnosing acute appendicitis was determined as 69%. The specificity was calculated as 60%, positive predictive value as 0.89, negative predictive value as 0.30, and accuracy as 0.67. Abdominal US is a helpful diagnostic tool for diagnosing acute appendicitis. However, it should not be seen as superior to anamnesis and physical examination findings.

Gastrointestinal tract schwannomas and brief review of literature.

Schwannomas originating from Schwann cells arise from the peripheral nerve sheath and are slow-growing, benign tumors that originate mostly from the mesenchyme. It appears equally in both sexes. Schwannomas are often seen in the 3rd and 5th decades of life. Schwannomas can be seen everywhere where peripheral nerves are seen. Gastrointestinal schwannomas constitute 2-6% of all submucosal masses, and the stomach is the most common region (60-70%). Endoscopic Ultrasound (EUS)-guided sampling of gastrointestinal submucosal lesions has made it possible to achieve preop- erative differential diagnosis. Patients diagnosed with gastrointestinal schwannomas between January 2005 and December 2017 were included in this study. Three out of six patients were females. Median age was 52.5 (44-76) years. Schwannomas were found in two patients in the gastric region, one patient in the appendiceal region, two patients in the colon and one patient in the perianal region. Primary schwannomas are usually benign. Radical resection with free margin is necessary because of the risk of malignant degeneration; chemo and radiotherapy response is indeterminate, and local recurrence rates are high.

Intracholecystic tubular non-mucinous neoplasm (ICTN) of the gallbladder: a clinicopathologically distinct, invasion-resistant entity.

Preinvasive tumor-forming gallbladder neoplasms that are composed of small, non-mucinous tubules with complex architecture remain a poorly characterized group. Here, we evaluated the clinicopathological characteristics of this entity. Twenty-eight examples were analyzed. Tumors were invariably pedunculated polyps with thin stalks, often presented as loosely attached intraluminal nodules, with cauliflower architecture (akin to cholesterol polyps) comprised of compact, back-to-back acinar-like, small tubular units with minimal/no cytoplasm showing variable complexity, creating a picture distinct from the other tubular type dysplasia in the gallbladder. Their limited stroma showed distinctive amorphous amyloid-like hyalinization (39%). While some had round nuclei with single prominent nucleoli, others exhibited slightly more elongated nuclei with washed out chromatin reminiscent of papillary thyroid carcinoma. Squamoid/meningothelial-like morules (71%) and subtle neuroendocrine cell clusters (39%) were frequent. The level of cytoarchitectural atypia qualified as high-grade dysplasia (HGD) in all cases, but none were invasive. The background mucosa showed no dysplasia, but cholesterolosis. The majority (n = 8/12) showed diffuse MUC6 expression and lacked MUC5AC expression. Based on these observations, 635 gallbladder carcinomas were re-analyzed for residual/adjacent lesions with entity-defining characteristics disclosed here, and none could be identified. Preinvasive tubular non-mucinous neoplasm of the gallbladder, which we propose to classify as intracholecystic tubular non-mucinous neoplasm, is a clinicopathologically discrete entity, which tends to occur in uninjured gallbladders and in association with cholesterol polyps. By being tubular, non-mucinous and MUC6-positive, it is akin to intraductal tubulopapillary neoplasms of pancreatobiliary tract, but it is also different in many other aspects. Although their cytoarchitectural complexity warrants an HGD/carcinoma classification, they do not show invasion and their distinct characteristics warrant their separate classification.

Epstein-Barr virus infection in patients with chronic gastritis without Helicobacter pylori infection.

BACKGROUND/AIMS: The association of Epstein-Barr virus (EBV) with gastric malignancies has been proven by many studies in the literature. However, information about EBV-associated inflammation/gastritis remains limited. The aim of this study is to establish the prevalence of latent EBV infection in patients with chronic gastritis without H. pylori infection. MATERIALS AND METHODS: In this study, 119 patients with gastritis without H. pylori infection were included. Furthermore, 28 patients with H. pylori gastritis were included in the study as a control group. Chromogenic in situ hybridization (EBV-encoded RNA) and immunohistochemistry (LMP-1 antibody) were performed in all 147 cases. The prevalence of EBV and its relationship with age, sex, the affected part of the stomach, the density of inflammation, inflammatory activity, intestinal metaplasia, and atrophy were analyzed. RESULTS: In this study, 14 cases showed positive immunostaining for EBV. EBV positivity was seen mostly in the lymphoid tissue (13 cases), but it was also detected at the gastric epithelium (7 cases). The mean age of the patients was 44 years, which was slightly younger than that of the EBV-negative cases (48 years). The inflammation density was higher in EBV-positive cases than the EBV-negative gastritis cases (p=0.002). Intestinal metaplasia was detected in 7% of the cases. EBV-positive cases had a higher incidence of atrophy without intestinal metaplasia (21% vs 3.8% without EBV). CONCLUSION: EBV was detected in 12% of the cases with gastritis without H. pylori infection. Endoscopic follow-up may be appropriate for patients with gastritis, who have atrophy without intestinal metaplasia and are H. pylori negative but EBV positive.

The Prognostic Value of 18F-FDG PET/CT and KRAS Mutation in Colorectal Cancers

Objective: Prognostic effect of KRAS mutation and side of tumor in colorectal cancer is a highly controversial subject. Therefore, we evaluated the association between FDG uptake pattern in 18F-fluoro-2-deoxy-glucose positron emission tomography/computed tomography (18F-FDG PET/CT) imaging and KRAS mutation and tumor localization in patients with a diagnosis of colon cancer and assessed the effects of these three factors on prognosis and survival. Methods: Eighty-three patients with colorectal cancer were retrospectively included in this study. 18F-FDG PET/CT study was performed for pretreatment staging. The maximum standardized uptake value (SUVmax) of the primary tumor and survival data of patients were compared between groups. KRAS mutations were detected with the help of real-time Polymerase Chain Reaction technique through genomic DNA extracted from paraffin-embedded tumor tissue blocks. Tumor lesions with potential KRAS mutations were classified as mutant KRAS and wild type. Results: Twenty five patients were female while 58 were male. The mean age of the patients was 59.8±11.3 years. Mean follow-up was 35.5±18.9 months. Primary tumor was localized in the left colon in 83.1% of patients and in the right colon in 16.9%. KRAS mutation was detected in 54.2% (n=45) of patients. Mean SUVmax of patients with primary tumor was estimated to be 21.1±9.1 (range= 6.0-47.5). Mean tumor SUVmax of patients with a KRAS mutation (24.0±9.0) was found to be significantly higher than those without KRAS mutation (17.7±8.2) (p=0.001). Mean survival was significantly shorter in patients with locoregional nodal metastasis than in patients without locoregional nodal metastasis as well as in patients with distant nodal metastasis than in patients without distant nodal metastasis and in patients with organ metastasis in initial PET/CT than in patients without organ metastasis. Also, mean survival was nearly statistically-significantly shorter in patients with tumors located in left colon (34.2±19.4) than in right colon (43.2±14.6) (p=0.059). However, we found no significant impact of KRAS mutation on survival. Conclusion: In our study, we found that tumor localization had no significant effect on prognosis in patients with colon cancer. On the other hand, FDG uptake was observed to be higher in the presence of KRAS mutation and it was concluded that coexistence of KRAS mutation with higher SUVmax is a negative prognostic factor.