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Aim: We evaluated the efficacy and safety of TAS-116, a novel class of an orally active selective inhibitor of heat shock protein 90, in patients with advanced gastrointestinal stromal tumour (GIST) after failure of three or more lines of standard treatment with imatinib, sunitinib and regorafenib., Methods: In this single-arm phase II study, patients received 160 mg/day oral TAS-116 for five consecutive days, followed by a 2-day rest. The primary end-point was centrally assessed progression-free survival (PFS). The secondary end-points were objective response rate, disease control rate, overall survival (OS), metabolic response rate, safety, pharmacokinetics and pharmacogenomics., Results: Forty-one patients were enrolled in Japan, and 40 patients underwent efficacy and safety evaluation. At the cut-off date, the median PFS was 4.4 months (95% confidence interval [CI], 2.8-6.0) and 12-week progression-free rate was 73.4% (95% CI, 58.1-88.7). Thirty-four patients (85.0%) had stable disease for ≥ 6 weeks. The median OS was 11.5 months (95% CI, 7.0-not reached). All patients experienced at least one treatment-related adverse event (AE), including diarrhoea (80.0%), decreased appetite (45.0%) and increase in blood creatinine level (42.5%). Grade ≥3 AEs and treatment-related grade ≥3 AEs occurred in 23 (57.5%) and 21 (52.5%) patients, respectively. All AEs resolved after dose modification, and no TAS-116-related AEs led to treatment discontinuation., Conclusion: TAS-116 showed significant activity in advanced GIST refractory to standard treatment. Further development of TAS-116 is warranted., Trial Registration: JapicCTI-163182., (Copyright © 2019 The Author(s). Published by Elsevier Ltd.. All rights reserved.)

Previously, we showed that the expression of potassium channel tetramerization domain-containing 12 (KCTD12), which was discovered by a proteomics approach, is associated with high-risk behavior of gastrointestinal stromal tumors (GISTs). Here, we examined the distribution and expression of this protein by immunostaining with a commercially available polyclonal KCTD12 antibody in GISTs (n = 64) and other types of malignancy (n = 168) to clarify its diagnostic and clinical significance. Diffuse KCTD12 immunoreactivity was found in most GISTs (52 cases; 81%). KCTD12 expression was observed primarily in vascular endothelial cells, Purkinje cells of the cerebellum, and some neurons scattered throughout the cerebral cortex. KCTD12 was absent from not only the interstitial cells of Cajal but also interstitial cells of Cajal hyperplasia that was encountered incidentally in colon diverticulitis. KCTD12 immunostaining was also seen in malignant peripheral nerve sheath tumors (2/10 cases; 20%), synovial sarcomas (2/10; 20%), solitary fibrous tumor (1/8; 13%), angiosarcoma (1/7; 14%), and colon adenocarcinoma (1/24; 4%). In survival analyses, the 5-year recurrence-free survival rate of patients without KCTD12 expression was only 16.7% compared with 95.6% in those with KCTD12 expression (P < .0001). Ki-67 and KCTD12 were significant predictors of recurrence-free survival, and KCTD12 expression provided additional information about recurrence-free survival after accounting for Ki-67 status. Overall, KCTD12 expression was specific for GISTs from neoplastic and nonneoplastic adult tissues other than brain and served as a predictor of GIST recurrence. These findings suggest that KCTD12 is a useful and reliable biomarker for both the diagnosis and prognosis of GIST., (Copyright © 2013 Elsevier Inc. All rights reserved.)

The author herein reports histopathologic features of 31 surgical cases of gastrointestinal stromal tumor (GIST) of the digestive organs. The 31 cases of GIST were diagnosed in our pathology laboratory. They consisted of 24 cases of gastric GIST, 1 case of hepatic GIST, 1 case of small intestinal GIST, 4 cases of colon GIST, and 1 case of rectal GIST. The age of the patients ranged from 56 year to 84 years with a mean of 71 years. Male to female ratio was 21:10. The presenting symptoms were gastrointestinal bleeding in 13 cases, abdominal pain and discomfort in 13 cases, and asymptomatic in 5 cases. Endoscopy and imaging modalities including US, CT and MRI were useful to detect the tumors in all cases, and biopsies confirmed the GIST diagnosis in 21 cases. The size of GIST ranged from 1 cm to 12 cm with a mean of 4.3 cm. Grossly, 23 cases were submucosal tumors, 6 serosa-side tumors, 1 solid tumor in the liver, and 1 rectal polyp. Histologically, 28 cases were of spindle cell type and 3 of epithelioid type. According to mitotic counts and tumor size, the malignant risk was very low in 4 cases, low in 14 cases, intermediate in 9 cases, and high in 4 cases. Immunohistochemically, all cases were positive for KIT and vimentin, 30 cases for CD34, and 4 cases for alpha-smooth muscle actin. None were positive for desmin and S100 protein. Ki-67 labeling ranged from 2% to 18%. P53 protein was negative in all cases. PDGFRA was positive in 20 cases among 24 cases examined. Genetic analysis using PCR-direct sequencing method was performed in 5 GISTs; all the 5 GISTs showed point mutations or deletions in KIT gene, but did not in PDGFRA gene. The 5 cases of GIST were positive for PDGFRA protein, suggesting that PDGFRA overexpression is not associated with PDGFRA gene mutations. Four of the 31 cases showed metastases. The chemotherapy was imatinib mesylate in 6 cases, and none in 25 cases. Four cases of high risk died of GIST, and 27 cases are alive now without tumors.

Purpose: Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal tumors of the gastrointestinal tract arising from Cajal's cells and expressing c-kit. In a consensus report, the clinical behavior of GISTs was categorized into risk classes according to the tumor size and mitotic count. We analyzed the risk categories based on GIST patients who underwent a surgical resection at our institute during a period of 15 years., Methods: We evaluated the risk categories of GISTs and analyzed the outcome and risk categories retrospectively. We presented the MIB-1 score of the tumor instead of mitotic counts for the evaluation of cellular growth because of inaccuracies regarding the mitotic counts., Results: Patients were classified into 4 cases of very low risk, 11 of low risk, 8 of intermediate risk, and 5 of high risk. Four high-risk patients showed recurrence as either liver metastasis or peritoneal dissemination. In addition, local recurrence occurred in one low-risk and one intermediate-risk patient each., Conclusion: Our cases confirmed the correlation between the risk categories and the prognosis. A complete resection with sufficient margin must be confirmed even in low-risk cases to prevent local recurrence. Since high-risk patients showed poor prognosis, the adjuvant treatment with chemotherapeutic regimens must therefore be further studied for high-risk patients.

Gastrointestinal stromal tumors (GISTs) are rare mesenchymal neoplasms with an annual incidence of approximately 10 to 20 per 1 million cases. Although pathologists have often observed incidental small GISTs in the stomach resected from patients with gastric cancer, no report on the real incidence of gastric GISTs is available. In this study, 100 whole stomachs resected from patients with gastric cancer were sectioned at 5-mm intervals and hematoxylin and eosin-stained slides (a mean of 130 slides for each case) were examined for microscopic GISTs. KIT (CD117), CD34, and desmin expression of the incidental tumors was evaluated by immunohistochemistry, and genomic DNA extracted from formalin-fixed and paraffin-embedded tumor tissues was analyzed for c-kit gene mutations in exon 11. In 35 of the 100 whole stomachs, we found 50 microscopic GISTs, all of which were positive for KIT and/or CD34 and negative for desmin. Most microscopic GISTs (45/50, 90%) were located in the upper stomach. Two of the 25 (8%) microscopic GISTs had c-kit gene mutations. Fifty-one leiomyomas with positive expression for desmin were observed in 28 of the 100 stomachs. Both leiomyomas and GISTs were found in 12 stomachs. These results indicate that microscopic GISTs are common in the upper portion of the stomach. Considering the annual incidence of clinical GISTs, only few microscopic GISTs may grow into a clinical size with malignant potential. Further studies are required to clarify the genetic events responsible for the transformation of microscopic GISTs to clinical GISTs.

Immunostaining depending on antigen-antibody specificity is the commonest approach for determining the localization of specific antigens in tissue sections. This procedure is applicable not only with frozen or specially fixed samples, but also has proved reliable with formalin-fixed paraffin-embedded tissue sections through improvement of antigen-retrieval. Immunostaining is thus firmly established as a tool for diagnostic pathology and in our institute multiple antibodies are applied for 13-15% of the cases examined, as well as H and E staining. With the standard approach, approximately 3 h is necessary from the beginning of deparaffinization till covering sections with the Envision system. We utilized intermittent microwave irradiation for 10 min during hybridization with primary and secondary antibodies in a special moist-chamber, to achieve all immunostaining steps within 1 h in 178 primary antibodies frequently used for diagnostic pathology. According to our 5 years experience, such microwave irradiation not only obtained significant specific staining for enhancing the specificity of antigen-antibody reactions, but also inhibited nonspecific binding. We present herein the details of the methodology and recommendations for its application with particular primary antibodies. This method can contribute to savings in time and energy, allowing pathologists to rapidly obtain diagnostic information.