Multiple gastric stromal tumors in a child without syndromic association lacks common KIT or PDGFRalpha mutations

Pediatric soft tissue tumor pathology: A happy morpho-molecular union

Since its foundation by remarkably talented and insightful individuals, prominently including Pepper Dehner, pediatric soft tissue tumor pathology has developed at an immense rate. The morphologic classification of tumoral entities has extensively been corroborated, but has also evolved with refinement or realignment of these classifications, through accruing molecular data, with many derivative ancillary diagnostic assays now already well-established. Tumors of unclear histogenesis, classically morphologically undifferentiated, are prominent amongst pediatric sarcomas, however, the classes of undifferentiated round- or spindle-cell-tumors-not-otherwise-specified are being dismantled gradually with the identification of their molecular underpinnings. Within recent years, for example, numerous subcategories of 'Ewing-like' round cell sarcoma have emerged. Such advances have provided the basis for novel diagnostic and prognostic sub-classifications. Efforts at defining cell- or lineage-of-origin for several tumor types have produced interesting insights especially for rhabdomyosarcoma. The remarkably early onset of pediatric sarcomas defies the theory necessitating stochastic accumulation of several somatic mutations for cancer development and indeed, these tumors may be remarkably genomically stable, often belying their aggressive nature. Much is coming to light recently regarding the role of epigenetic modifications in the evolution of these sarcomas. Indeed the morphologic features of embryonal tumors generally (not just sarcomas) may be highly reminiscent of arrested differentiation, and given the tight epigenetic regulation of cell fate determination and cell identity maintenance, a theory of epigenetically-driven oncogenesis sits easily with these tumors. The age-delimited distinct biologies of 'pediatric' and adult GIST are intriguing, particularly, the SDH-deficient 'pediatric' form, driven by a metabolic defect, but resulting in epigenetic dysregulation with genome-wide DNA methylation changes. There is little doubt that many of the gaps in our understanding of pediatric sarcoma biology will be filled by a deeper appreciation of the role of dysregulated epigenetics including chromatin biology, perhaps best exemplified in malignant rhabdoid tumor. The field of pediatric soft tissue tumor pathology grows ever more interesting. Importantly though, it must be emphasized, that none of this progress could have occurred, or indeed continue, without the initial step of accurate diagnosis, founded solidly on morphology - thank you Pepper for your unparalleled contributions to this field! The opportunity to be your apprentice for five years has been a bigger and more positive influence than words can express.

Incidental GIST after appendectomy in a pediatric patient: a first instance and review of pediatric patients with CD117 confirmed GISTs

A 7-year-old boy underwent uncomplicated laparoscopic appendectomy for acute appendicitis. Incidentally, he was found to have a spindle cell tumor with CD117 immunopositivity, consistent with gastrointestinal stromal tumor (GIST) in the appendix. Although commonly reported in adults, pediatric GISTs are rare gastrointestinal malignancies that occur in only 1.4-2.7% of children and adolescents. Due to the paucity of reports, data are insufficient to adequately characterize tumor behavior, recurrence, and survival. We present the first case of pediatric GIST in the appendix. In addition, a review of the literature for CD117 confirmed pediatric GISTs was conducted to summarize its clinical features and current treatment options.

Gastrointestinal stromal tumor of the stomach in a child with a 3-year follow-up period-Case report

We report a case of a nine-year-old boy with a 4-week history of general fatigue, loss of appetite, vomits and hematemesis. Laboratory evaluation revealed a hemoglobin level of 4.4 g/dl. After a transfusion of packed red blood cells the patient underwent an esophagogastroduodenoscopy, which showed a smooth, rounded 6-8 cm submucosal lesion with a central depression with ulceration and active bleeding in the cardia extending to the fundus.Computed tomography (CT) of the chest, abdomen and pelvis showed a large mass originating from the gastric wall but not infiltrating surrounding organs, approximately 8.0 cm × 7.0 cm × 5 cm. Despite the tumor size, no metastases were diagnosed. The patient underwent a total gastrectomy in an en-bloc resection including the distal part of the esophagus (3 cm) and omentum with oncologic margins. Reconstruction was performed with a mediastinal end-to-side esophago-jejunal anastomosis. Immunehistochemic confirmed GIST. He remains well without evidence of disease after 36 months of follow-up with a multiprofessional team.

Gastrointestinal stromal tumors (GIST) in children and adolescents: A comprehensive review of the current literature

Standards for the management of gastrointestinal stromal tumors (GIST) in children do presently not exist. Thus a systematic review and summary of the current literature was conducted serving as a basis for the further development of optimal management strategies for childhood GIST within a cooperative network. Presently 21 cases with familial GIST, and more than 100 pediatric cases each with Carney triad or sporadic GIST have been published so far. An international prospective registration based on national registries has recently started to acquire more clinical and molecular data and to develop appropriate management strategies for children and adolescents with GIST.

Clinical and molecular characteristics of gastrointestinal stromal tumors in the pediatric and young adult population

Gastrointestinal stromal tumors (GISTs) typically occur late in life; however, there also are reports of pediatric and young adult patients. This rare subset of GISTs has clinicopathologic and molecular features distinct from their adult counterparts. Most pediatric GIST patients are female and often present with multifocal tumors that are epithelioid in nature. Although these young patients often have metastatic disease, it progresses slowly. Most pediatric GISTs lack the gain-of-function mutation in KIT or PDGFRA commonly found in adult cases. Expression profiling and genomic studies of pediatric GISTs show distinct molecular signatures, suggesting a unique origin as compared with adult GISTs. We and others have shown that the insulin-like growth factor 1 receptor may have a prominent role in driving KIT/PDGFRA mutation-negative adult and pediatric GISTs, and clinical trials are currently being designed to exploit these types of discoveries.

Pediatric gastrointestinal stromal tumors

Gastrointestinal stromal tumors (GISTs) rarely occur in pediatric patients, but increased recognition of adult GIST has led to better awareness of the existence of this entity in the pediatric population. GIST occurring in pediatric patients has a unique biology and clinical behavior and warrants discussion as an independent entity. The generally accepted definition of pediatric GIST is a tumor that is diagnosed at the age of 18 years or younger. This review highlights the clinical features, molecular biology, and clinical management of this rare pediatric entity.

E, Hirai T, Nakajima K, Nishitani A, Souma Y, Sawa Y, Nishida T. Aberrant expression of glycosylation in juvenile gastrointestinal stromal tumors

Most adult gastrointestinal stromal tumors (GIST) are thought to be caused by activating mutations in the KIT or PDGFRA gene. However, many juvenile GIST lack either mutation and are considered to develop with a different pathogenesis. To investigate the molecular characteristics of juvenile GIST, we analyzed the proteome difference in phosphorylated protein between adult and juvenile GIST. Eleven GIST samples (seven adult cases and four juvenile cases lacking either mutation) were analyzed by using immunostaining and LC‐MS/MS. Comparative analysis of tyrosine‐phosphorylated protein levels showed that juvenile GIST possessed phosphorylated KIT in spite of lacking mutation in the KIT gene. Moreover, downstream signals of KIT were also activated as in adult GIST. Although, SDS‐PAGE gels showed that there was a difference of each KIT bands between adult and juvenile GIST, they became the same after removal of N‐glycans or sialic acids. Moreover, one of the most typical enzymes, ST6Gal1, which transfers Neu5Ac residues in α2‐6 linkage to Gal β1‐4GlcNAc units on N‐glycans, is significantly less expressed in juvenile GIST. This suggests that the difference in KIT is generated by post‐translational modification and may play a role in the progression of juvenile GIST.

Clinical significance of oncogenic KIT and PDGFRA mutations in gastrointestinal stromal tumours

Gastrointestinal stromal tumours (GISTs) are the most common mesenchymal neoplasms of the gastrointestinal tract. Despite clinicopathological differences, GISTs share oncogenic KIT or platelet-derived growth factor-alpha (PDGFRA) mutations. Imatinib, KIT and PDGFRA inhibitor, has been successfully used in the treatment of metastatic GISTs. There are primary KIT or PDGFRA mutations diagnosed before imatinib treatment, linked to GIST pathogenesis, and secondary mutations detected during treatment, causing drug resistance. KIT exon 11 mutations are the most common. Gastric GISTs with exon 11 deletions are more aggressive than those with substitutions. KIT exon 11 mutants respond well to imatinib. Less common KIT exon 9 Ala502_Tyr503dup mutants occur predominantly in intestinal GISTs and are less sensitive to imatinib. An Asp842Val substitution in exon 18 is the most common PDGFRA mutation. GISTs with such mutation are resistant to imatinib. PDGFRA mutations are associated with gastric GISTs, epithelioid morphology and a less malignant course of disease. GISTs in neurofibromatosis 1, Carney triad and paediatric tumours generally lack KIT and PDGFRA mutations. Secondary KIT mutations affect exons 13-17. GISTs with secondary mutations in exon 13 and 14 are sensitive to sunitinib, another tyrosine kinase inhibitor. KIT and PDGFRA genotyping is important for GIST diagnosis and assessment of sensitivity to tyrosine kinase inhibitors.

Coexistence of gastrointestinal stromal tumors with other neoplasms

BACKGROUND

The purpose of this study was to assess the prevalence of other neoplasms in patients with gastrointestinal stromal tumors (GISTs) and to compare clinical and histopathological data in patients with a GIST and accompanying neoplasms and in patients with GIST only.

METHODS

The analysis encompassed 82 patients with a GIST from among 330 300 patients whose surgical specimens, biopsies, and autopsies were evaluated between January 1989 and June 2006. A subgroup of patients with other types of neoplasms was selected.

RESULTS

Other neoplasms in patients with a GIST were diagnosed in 22 of the 82 (26.8%) patients. The most common accompanying neoplasms were colorectal (nine cases) and gastric (four cases) adenocarcinoma, as well as pancreatic adenocarcinoma (three cases). There was a tendency toward more common localization of a GIST in the small intestine in patients with other neoplasms than in patients with a GIST alone (P < 0.09). Tumors with very low risk of aggressive behavior were more frequent in patients with a GIST accompanied by other neoplasms than in the other group (P < 0.05). No phenotypic differences in GIST cells were found between the two groups.

CONCLUSIONS

In almost 27% of the study population, GISTs coexisted with other neoplasms. A greater proportion of patients with a GIST localized in the small intestine and/or characterized by a very low risk of aggressive behavior and accompanying other neoplasms, compared with a GIST alone, most likely reflects the fact that in the first group, GISTs tended to be an incidental finding during surgery. The results were affected by patient selection and the type of tissue material available.

KIT and PDGFRA mutations in gastrointestinal stromal tumors (GISTs)

Mutually exclusive KIT and PDGFRA mutations are central events in GIST pathogenesis, and their understanding is becoming increasingly important, because specific treatment targeting oncogenic KIT and PDGFRA activation (especially imatinib mesylate) has become available. KIT mutations in GIST are clustered in four exons. Most common are exon 11 (juxtamembrane domain) mutations that include deletions, point mutations (affecting a few codons), and duplications (mostly in the 3' region). The latter mutations most often occur in gastric GISTs. Among gastric GISTs, tumors with deletions are more aggressive than those with point mutations; this does not seem to hold true in small intestinal GISTs. Exon 9 mutations (5-10%) usually are 2-codon 502-503 duplications, and these occur predominantly in intestinal versus gastric GISTs. Lesser imatinib sensitivity of these tumors has been noted. Kinase domain mutations are very rare; GISTs with such mutations are variably sensitive to imatinib. PDGFRA mutations usually occur in gastric GISTs, especially in the epithelioid variants; their overall frequency is approximately 30% to 40% of KIT mutation negative GISTs. Most common is exon 18 mutation leading Asp842Val at the protein level. This mutation causes imatinib resistance. Exon 12 and 14 mutations are rare. Most mutations are somatic (in tumor tissue only), but patients with familial GIST syndrome have consitutitonal KIT/PDGFRA mutations; >10 families have been reported worldwide with mutations generally similar to those in sporadic GISTs. GISTs in neurofibromatosis 1 patients, children, and Carney triad seem to lack GIST-specific KIT and PDGFRA mutations and may have a different disease mechanism. Secondary mutations usually occur in KIT kinase domains in patients after imatinib treatment resulting in resistance to this drug. Mutation genotyping is a tool in GIST diagnosis and in assessment of sensitivity to kinase inhibitors. This is a US government work. There are no restrictions on its use.