The detection of ews/fli 1 translocation, n-myc amplification and pten mutation by fish method , the use of these parameters for differential diagnosis and the evaluation of c-kit (cd 117) expression in small round blue cell tumors

Although small round blue cell tumors (SRBCT) show histological similarities, their biological behaviors and treatment vary significantly. The differential diagnoses of these tumors may require electron microscopic and molecular studies as well as clinical information, knowledge on radiological features and immunohistochemistry. In the present study, a total of 57 cases, 32 being males and 25 being females, diagnosed in SRBCT group in Gazi University, Faculty of Medicine, Department of Pathology were examined. The most common localization was head and neck region and the mean age at presentation was 14.8 years. 24 of these cases (42.1%) were ES/PNET, 12 (21.1%) were rhabdomyosarcoma (RMS), 10 (17.4%) were neuroblastoma (NB), 2 were olfactory neuroblastoma (ONB), 1 (1.8%) was desmoplastic small round blue cell tumor (DSRBCT), 1 (1.8%) was polyphenotypical round cell tumor (PRCT) and 7 was undifferentiated small round blue cell tumor (USRBCT). Important conclusions of the study: (1) CD-99 positivity was detected in 63.2% of ES/PNET cases and this immunoreactivity was found in 1 PRCT, 2 USRBCT and 2 RMS cases. It was concluded that positivity with CD-99 was highly sensitive for ES/PNET family without being specific and CD-99 should be used as a part of the immonuhistochemical panel. Moreover, CD-99 was positive in none of the neuroblastoma cases whereas vimentin was negative as well in all cases of neuroblastoma and it was concluded that specific membranous CD-99 immunoreactivity and positivity with vimentin might be helpful in the differential diagnosis of ES/PNET. (2) CD-99 was found to be negative in 85.7% of central PNETs and a statistically significant difference between central and peripheral PNETs was detected for CD- 99 immunoreactivity (p=0.02). Furthermore, there was a significant difference in EWS/FLI1 between 11 cases which were accepted as central PNETs and between ES/PNET cases localized in other regions (p=0.04). It was suggested that negativity of CD-99 and EWS/FLI1 translocation in central PNETs might be helpful in distinguishing between peripheral PNETs. (3) EWS/FLI1 translocation was found in 65% of ES/PNET cases and it was decided that this percentage was actually lower since most of the cases were central PNETs and detection of EWS/FLI1 translocation would be quite sensitive for ES/PNETs. (4) N-myc amplification was detected in 4 of 10 cases of NB whereas 3 cases of NB exhibited N-myc overamplification and the ratio of N-myc amplification was found to be 70%. (5) It was detected that PTEN deletion was not found in SRBCTs except for PRCTs. (6) The ratios of Ckit expression were 49.8%, 58.4% and 88.9% in ES/PNET, RMS and NB cases respectively. It was concluded that specific treatment protocols against this expression might be used in SRBCTs. However these results should be confirmed with future studies in which treatment results are evaluated as well.