Inflammatory Myofibroblastic Tumor In Children Research Articles

Gastrointestinal stromal tumors--definition, clinical, histological, immunohistochemical, and molecular genetic features and differential diagnosis.

Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal tumors of the gastrointestinal (GI) tract. They are defined here as KIT (CD117, stem cell factor receptor)-positive mesenchymal spindle cell or epithelioid neoplasms primary in the GI tract, omentum, and mesentery. GISTs typically present in older individuals and are most common in the stomach (60-70%), followed by small intestine (20-25%), colon and rectum (5%), and esophagus (<5%). Benign tumors outnumber the malignant ones by a wide margin. Approximately 70% of GISTs are positive for CD34, 20-30% are positive for smooth muscle actin (SMA), 10% are positive for S100 protein and <5% are positive for desmin. The expression of CD34 and SMA is often reciprocal. GISTs commonly have activating mutations in exon 11 (or rarely exon 9 and exon 13) of the KIT gene that encodes a tyrosine kinase receptor for the growth factor named stem cell factor or mast cell growth factor. Ligand-independent activation of KIT appears to be a strong candidate for molecular pathogenesis of GISTs, and it may be a target for future treatment for such tumors. Other genetic changes in GISTs discovered using comparative genomic hybridization include losses in 14q and 22q in both benign and malignant GISTs and occurrence in various gains predominantly in malignant GISTs. GISTs have phenotypic similarities with the interstitial cells of Cajal and, therefore, a histogenetic origin from these cells has been suggested. An alternative possibility, origin of pluripotential stem cells, is also possible; this is supported by the same origin of Cajal cells and smooth muscle and by the common SMA expression in GISTs. GISTs differ clinically and pathogenetically from true leiomyosarcomas (very rare in the GI tract) and leiomyomas. The latter occur in the GI tract, predominantly in the esophagus (intramural tumors) and the colon and rectum (muscularis mucosae tumors). They also differ from schwannomas that are benign S100-positive spindle cell tumors usually presenting in the stomach. GI autonomic nerve tumors (GANTs) are probably a subset of GIST. Other mesenchymal tumors that have to be separated from GISTs include inflammatory myofibroblastic tumors in children, desmoid, and dedifferentiated liposarcoma. Angiosarcomas and metastatic melanomas, both of which are often KIT-positive, should not be confused with GISTs.

Abdominal inflammatory myofibroblastic tumors in children: Report of an appendiceal case and review of the literature

Inflammatory myofibroblastic tumors (IMT) are rare, benign lesions. They mimic, clinically and radiologically, malignant tumors—especially sarcoma. IMT most often are seen in the lung of young adults, but there have been reports of these tumors occurring in children, in various sites. The authors report a case of appendiceal IMT arising in a 15-year-old boy previously treated for inherited distal renal tubular acidosis. He was admitted because of anorexia, weight loss, and a low-grade fever. The ultrasound study showed bilateral hydroureteronephrosis, with a poorly functioning right kidney noted on intravenous urography, and a retrovesical soft-tissue mass. Laboratory studies showed renal insufficiency, an elevated white blood cell count, anemia, thrombocytosis, and hypergammaglobulinemia. During laparotomy, a pelvic appendiceal mass was discovered, appendectomy was performed, and the pathological diagnosis of inflammatory myofibroblastic tumor was made. Three months later the boy was well, and the biological, sonographic, and urographic results had returned to normal. A review of 74 cases of abdominal IMT occurring in childhood emphasizes the importance of pathological differentiation of these lesions from malignancy, with early total excision whenever possible. Long-term follow-up is necessary to detect local recurrence, which may develop many years later, and to confirm the allegedly benign nature of these tumors.