Aim: Determination of frequency of patologic findings and types of pathologic findings in enteric nerve plexus (ENP) in colon biopsies in children with impaired bowel motility, specifically chronic constipation. Introduction: Chronic constipation is relatively common in children, and is most often a functional disorder that is responsive to dietary regime treatment. Rarely, some cases require biopsy and histopathologic analysis of ENP. Materials and Methods: Research consists of 299 colon biopsies taken from children with impaired bowel motility. Biopsies were analysed in Institute of pathology, Medical faculty in Belgrade, in the period of time from the year 2008 to 2018. Data analysis included standard methods of descriptive and analytic statistics. Results: Number of analysed biopsies was 588. Biopsies were taken from 184(61,5%) boys and 115(38,5%) girls. Most common referral diagnosis for biopsy was Hirschspung’s disease (HD) (153/299, 51,2%). Pathologic changes in ENP were found in 46,1% of patients (138/299). Histopathologic analysis confirmed clinical suspicion for HD in 48,4%(74/153) of patients. Most frequent pathologic finding secondary to HD were immature ganglion cells (26/299, 8,7%), ectopic position of ganglia in muscle layer of colonic wall (6/299, 2%), and unclassified dysganglioses (5/299, 1,7%). In six patients, cause of constipation was eosinophilic proctitis and/or mienteric ganglionitis. Acetilcholin esterase as diagnositic metod was applied in 29 patients. Immunohistochemical analises were used in 24 patients. Conclusion: HD and immaturity of ganglion cells are by far most frequently diagnosed causes of constipation in colon biopsies in pediatric patients. Eosinophilic proctitis and/or mienteric ganglionitis are rare causes of constipation in children.

Aim: We present the case of a rare localization of the alveolar soft part of the sarcoma in the visceral organ. Introduction: Alveolar soft part sarcoma (ASPS) is a rare mesenchymal tumor typically occurring in young patients, more frequently in females. Common localization of ASPS is skeletal musculature of lower extremities. ASPS in visceral organs usually represents a metastasis from the more common primary location in skeletal muscles. ASPS is characterized by a tumor-specific translocation which causes the fusion of the TEF3 with a ASPL gene (also known as ASPSCR1). Case report: Female 47 years old was admitted to hospital due to abdominal pain. Urgent surgery was performed due to ileus. Ileal tumor was detected intraoperatively as a cause of ileus. Tumor was infiltrated whole intestinal circumference, with dimension 70mm x 47cm and evident perforation. Histology showed well-defined nests of pleomorphic cells separated by delicate fibrovascular septae. Within described nests there is a prominent lack of cellular cohesion, representing for the distinctive pseudoalveolar pattern. Immunohistochemical stadies were diffusely positive for TFE3 and focally positive for CD34 and alpha-SMA and negative for panCK, DOG-1, CD117, S-100, HMB45, Desmin. Immunopositivity for Ki67 was present in 20% of tumor cells. FISH analysis was done using locus specific dual color break-apart TFE3 (3 and 5 ) probe and rearrangement in the TFE3 gene was confirmed. Conclusion: Despite the fact that ASPS is rare mesenchymal tumor in visceral organs it have to be considered as possible diagnosis especially in cases with typical histological features and immunohistochemical profile. Definitive diagnosis of ASPS must be confirmed by FISH analysis.

Aim: We present a rare case of gastrointestinal tumor in a boy. Introduction: Gastrointestinal stromal tumors (GISTs) represent rare mesenchymal tumors in pediatric population. Most of these tumors originate in the stomach and very rarely in the oesophagus. They are more frequent in young girls. As opposed to adult GISTs, those that occur in childhood show mutations in PDGFRA receptors or so called “Wild type” mutations. Case report: A fifteen years and 2 months old boy with symptoms of dysphagia and stenocardia for the last six months. Endoscopy showed nodular solid lesion at the distal part of the thoracal oesophagus, later surgically removed. Dimensions of the lession were 35x25x20mm with whitishPOSTER SESIJA 57 MATERIA MEDICA • Vol. 34 • Issue 1, suplement 1 • april 2018. yellow cut surface and areas of hemorrhage. Histology showed predominant spindle cell pattern with minor epithelioid component, with pronounced cellular and nuclear pleomorphism, rare areas of necrosis and hemorrhage, with the mitotic count more than 18 per 50 high power fields and numerous atypical mitotic figures. Immunohistochemical studies were CD117 and DOG-1 negative, but positive for PDGFRA. Tumor expressed focal alpha-SMA and CD34 positivity. Conclusion: Informations regarding pediatric gastrointestinal stromal tumors are still insufficient. Even though these tumors are rare in childhood, when analysing mesenchymal neoplasms potential GISTs should be considered.