Clinicopathologic Characterization Of Small Gastrointestinal Stromal Tumors And The Expression Of Parathyroid Hormone-related Protein

BackgroundGastrointestinal stromal tumors represent the most commom gastrointestinal mesenchymal tumors of gastrointestinal tract, with their annual incidence of approximately 10 to 20 per million cases. Gender or racial difference was not significant.It could be at any part of gastrointestinal tract,especially in stomach and small intestine.Majority of GISTs have an gain-of-function mutation in the c-kit gene and express the phosphorylate receptor tyrosine kinase KIT,which make them to be a separate and distinct group from other gastrointestinal mesenchymal tumors. The activation of tyrosine kinase receptor KIT mainly involves KIT (85%) and platelet-derived growth factor receptor alpha (PDGFRA) gene mutation. These mutations can activate the corresponding receptors, resulting in cell signal transduction pathway dysfunction and cell growth, proliferation out of control.As a first-line drug of treatment for GISTs, Small molecule tyrosine kinase inhibitor imatinib has greatly improved the survival rate.From small inertia stromal tumors to fatal sarcoma,GISTs have a great heterogeneity, which brings challenge to predict benign or malignant tumor. Classification of these tumors is still remains a matter of controversy, although a variety of judgment standards appeared according to tumor size, location and proliferation activity. With the development of endoscopic techniques, the detection rate for small preclinical gastrointestinal stromal tumors increased significantly. Although this part of small GISTs have a lower mitotic index, Tumor metastasis is still possible. Subsequently,the point that all gastrointestinal stromal tumors has malignant potential was proposed.Own to its inert biological behavior, the small stromal tumors was easy to be ignored. Meanwhile, without a clear demarcation based on size,the definition has always been subjective and random,until NCCN guidelines defined the tumors less than 2cm as "very small GISTs" in 2010. Later, The new revision of the 2013 China expert consensus suggested"tiny GISTs"when it comes to the tumors no more than 1cm.Now following the development of endoscopic technique,it has successfully attracted the attention of Clinical doctors with a significant difference between its higher detection rate and lower incidence of overt GISTs. The histological structure and immunohistochemical features of small GISTs is similar to that of a surgical resection GISTs. When the phenomenon that KIT gene mutations are common in small stromal tumors revealed,it was thought that this group may represent the early stage of clinical stromal tumors. However, there are also opposite studies suggested that besides other rare and new mutations,the over all KIT/PDGFRA gene mutation rate in small GISTs, especially the mutation in exon 11, was significantly lower than the overt GISTs. Combining with the special pathological features, they thought small stromal tumor were more inclined to self-limited disease.In 2013, Chinese gastrointestinal stromal tumor diagnosis and treatment expert consensus suggested resection of small GISTs should be consided on the conditions that the patient present symptoms and the endoscopic ultrasound shows adverse factors (the edge is irregular, ulcers, strong echoes and heterogeneity),or abandon surgrey to recheck it every 6 to 12 months.An recent research showed that majority of the patients suffering from indigestion(94.2%) could relieve after the surgery of Endoscopic submucosal dissection, and only 2 cases (3.8%) have no obvious improvement. Beside the interference from other gastrointestinal disease, they thought that symptoms was associated with their stromal tumors. Since all GTSTs has malignant potential and the natural progression, mitotic index and gene mutation spectrum of small GISTs are uncertain, some scholars put forward surgical resection should be taken into consideration for the treatment of small GISTs once found.The NCCN has pointed out that laparoscopy can be used to treat the stromal tumors at specific sites, but no clear description for endoscopic therapy.Prognostic factors of GISTs are complex. Besides the size and the mitotic index, it may also involve other Clinicopathologic and morphological features, even do with the gene mutation, expression, and deletion. Some target protein related to cell proliferation may provide a new research field.Parathyroid hormone-related protein (PTHrP) is a cytokine,which was originally identified as a causative factor of malignant humoral hypercalcemia. Sharing a similary structure with Parathyroid hormone(PTH), it mainly works through autocrine and paracrine form. As early as in 2004 it has confirmed PTHrP could highly expressed in GISTs (total 19 GISTs were positive for PTHrP,95% of which were strong), and the coexpression of PTHrP and PTH/PTHrP-R may play a important role the in the growth and differentiation of GISTs. we further give a refinement for the expression lever of PTHrP in small GISTs (d<2cm) and GISTs (d≥ 2cm), intending to provide GISTs a new way for the research of clinical pathological characteristics and standardize treatment.ObjectiveThe clinical pathological characteristics and endoscopic treatment for small GISTs have still been in controversial, further research on this controversy and the mechanism of some new targets, not only can improve knowledge of GISTs, detect earlier, prevent progression, but also benift for individualized treatment and guide the treatment of different stages,maximize the prognosis and survival rate. Starting from the basic clinical data and the existing knowledge of small GISTs,combining our previous work for PTHrP, we did a preliminary research from there parts:clinicopathological characteristics of small GISTs, Values of endoscopical therapy for small gastric stromal tumor and expression of parathyroid hormone-related protein in gastric stromal tumor.Materials and methods1. Materials1.1 Medical records of the patients dignosed with GISTs by pathology and immunohistochemistry in Nanfang hospital during October 2003 to June 2014 were retrospectively analyzed. The patient experienced endoscopy or laparoscopy or laparotomy surgery.Last investigation was in December,2014.Eliminate standards include:(1) the diameter of tumor was 2.0cm or more;(2) the mass outside of the gastrointestinal tract;(3)experienced surgery, but failed to reach R0 resection;(4) targeted drugs were used for therapy;(5) patients failed to reach discharge standard but discharged on his own will;(6) lost to follow-up early(< 12 months);(7) follow-up information is not complete.95 cases were selected to study the first part: clinicopathological features of small GISTs1.2 Medical records of the patients dignosed with GISTs by pathology and immunohistochemistry in Nanfang hospital during October 2003 to June 2014 were retrospectively analyzed. The patient experience endoscopy or laparoscopy or laparotomy surgery.Last investigation was in December,2014.Eliminate standards include:(1) maximum diameter was 2.0 cm or more;(2)coexistence GISTs outside of stormach at the same time;(3) with other diseases that experienced endoscopic or laparoscopy or laparotomy surgery simultaneously;(4)receive anti-tumor treatment intraoperative and postoperative;(5) failed to reach discharge standards to discharge on his own will;(6) lost to follow-up early (follow-up time< 12 months), and follow-up data is not complete;(7) other conditions may affect the treatment effect and safety.80 cases were used to study the second part:Values of endoscopical therapy for small gastric stromal tumor.1.3 21 paraffin blocks of the above case were available, at the same time, collect and the embed 17 GISTs specimens(d≥ 2cm) that hospitalized and experience surgrey in April 2014 to July 2014.All cases were diagnosed with GISTs.22 corresponding surface mucosal tissues of GIST were available to analy the expression of PTHrP.2 Method and statistical analysis2.1 Medical records of the 95 small GISTs were retrospectively analyzed and summarized their gender, age, symptoms, tumor size, location, mitotic index, pathological and immunohistochemical features, endoscopic and endoscopic ultrasonography characteristics, and classified all the cases according to the revision of the 2008 NIH risk classification,.Then assessed the relationship between the factors and risk classification with chi-square statistics and exact probabilities in fourfold table test.2.2Medical records of the 80 cases of gastric stromal tumors were retrospectively analyzed and summarized their gender, age, symptoms, history of previous abdominal surgery, tumor size, mitotic index, gastroscope and ultrasonic characteristics, therapy methods etc.Compared the complete resection rate, the incidence of postoperative complications, the improvement of postoperative symptoms, operation time, intraoperative blood loss, postoperative eating time, postoperative hospital stay and hospital expenses between endoscopic treatment group and the surgical treatment group.T test or separate variance estimation T test was applied for difference comparision among measurement date,while chi-square statistics or exact probabilities in fourfold table test was applied for count data.2.3 Immunohistochemical method and score were performed to detect the expression of PTHrP, Mann-Whitney U test was respectively used to compare the PTHrP expression in small gastric stromal tumor and gastric stromal tumor.All data adopt SPSS20.0 statistical software for statistical analysis, all the statistical results with P<0.05 for a significant difference.3 Result3.1 Analysis of clinical characteristics of Small gastrointestinal stromal tumor: 83.2%(79/95) small GISTs arised from stomach, including 86.1%(68/79) in middle-upper stomach. The risk factors of EUS had no statistically difference with mitotic count (P>0.05). Positive rate of CD34 and CD117 was 95.8% and 96.8% respectively.5 cases coexisted with gastrointestinal cancers and 5 cases presented calcification, all of which MI>5/50HPF;2 case presented arrangement of epithelioid cells, with MI>5/50HPF.92.6% small GISTs were very low and low grade of NIH risk classification. The tumors up to 1.5cm had a striking correlation with NIH risk classification(P<0.05),while positive Ki67 had nothing to do with it (P>0.05).82 patients was followed up for 15 to 133 months, median time was 43.5 months.No progress、recurrence、metastasis and death were found at the end of follow-up.3.2 Comparison between endoscopic resection and surgical treatment for small gastric stromal tumor:35 cases(94.6%) of endoscopic treatment group successfully treated by endoscopic surgery.8 cases showed intraoperative perforation, among which 2 cases were transferred to the conventional operation; Pneumoperitoneum was recorded in 2 cases (better after symptomatic treatment), while no serious infection and perioperative death happened. There were no significant differences in the rate of complete resection [91.89%(34/37),100.0%(43/43), P=0.095), the incidence of postoperative complications [5.71%(2/35),2.33%(1/43), P=0.855) and the improvement of postoperative symptoms [93.10%(27/29),85.71%(30/35), P=0.589], while statistically significant differences were found in operation time [(37.41±13.45)min:(84.56±38.37)min, P=0.000)], intraoperative blood loss [(5.65±5.88)ml:(31.48±39.57)ml,P=0.000)], postoperative eating time [(2.47±0.61)d:(3.26 ±1.27)d, P=0.001)], postoperative hospitalization time [(5.76 ±2.28)d:(7.64±2.99)d,P=0.022], and hospitalization expenses [(18554.4±9736.45)yuan:(31138.11±1206.24)yuan, P=0.000].3.3 The expression and statistical analysis of PTHrP in normal gastric mucosa, muscularis propria, surface mucosa layer of gastric stromal tumor and GISTs:The immunostaining of PTHrP in the 9 (100%)normal gastric mucosa tissues were all strong,while in the 7 normal gastric muscularis propria tissues showed weak stain in 1 case (14.3%),moderate stain in 2 cases (28.6%) and strong stain in 4 cases (57.1%);14 cases of the surface gastric mucosal tissue of small GIST showed weak stain in 2 cases (14.3%),moderate stain in 6 cases (42.9%) and strong stain in 6 cases (42.9%);8 cases of surface mucosa tissues of gastric stromal tumor showed moderate stain in 2 cases (25%) and strong stain in 6 cases (75%).The expression of PTHrP in the surface mucosal tissue of gastric stromal tumor was lower than normal mucosal tissue (P< 0.05), while no statistical differences were found between the other two groups(the surface mucosal tissue of GIST and normal mucosal tissue,the suface mucosal tissue of small GIST and the suface mucosal tissue of GIST,P>0.05).The immunostaining of PTHrP in 21 small GIST(d<2cm) showed no signal stain in 3 cases, weak stain in 5 cases,moderate stain in 6 cases,and strong strain in 7 cases.In contrast,PTHrP immunostraining in GIST(d^ 2cm) showed no and weak strain in 0 case,moderate strain in 8 cases,strong strain in 9 cases. PTHrP expression in small gastric stromal tumors was lower than gasric stromal tumor(p<0.05).Conclusion1 Most Small GISTs,single or multiple,are located at middle-upper stomach with very low or low risk, enjoying a favorable prognosis.But it has a worse biological behavior and a higher grade risk when the diameter is more than 1.5cm.2 Endoscpic resection is safe and effective for small grastric stromal tumor with the advantages of minimally invasive and simple in operation, and that patients can enjoy a rapider recovery and a lighter economic burden.3 PTHrP can express in normal gastric mucosal tissue and muscularis propria tissues,and the immunohistochemistry expression of PTHrP in gastric GIST is different (from no stain,weak stain to strong stain), and the expression in small gasric stromal tumor and gastric stromal tumor has statistical difference,which not only shows heterogeneity of the tumor,but also reveals that PTHrP may play an important role in tumor growth and development.Further study is needed to confirm their reason,significance and mechanism.