Within soft-tissue sarcoma, primitive neuroectodermal tumors have been shown to cover a wide spectrum of small round cell sarcomas, including Ewing's sarcomas (ES) and primitive neuroectodermal tumors (PNET). The role of the stem cell factor/kit pathway has been investigated in different human tumors especially in chronic myelocytic leukemia and gastrointestinal stromal tumor and an autocrine loop has been assumed in small cell lung carcinoma, and recently in ES and PNET. Our aim is to investigate the c-kit expression in ES and PNET and also to assessed if c-kit has any role in disease process.
We thoroughly searched the archives of the Department of Pathology, Faculty of Medicine, Cukurova University Turkey, between 2000 and 2004; and found 14 ES and 14 PNET paraffin embedded tissues. We carried out the detection of the c-kit expression by immunohistochemical staining.
The patient's median age was 23.7 +/-14.6 (12 male and 16 female). Five were diagnosed as metastatic disease whereas 23 were diagnosed as non-metastatic disease at admission. The mean follow up period was 38.9 +/- 22.3 months. The main localization of the disease was lower extremity (32.1%), and others were as follows: head and neck 25%, thorax and abdomen 14.3%, pelvic and upper extremity 7.1% (11 were localized skeletal and 17 were extraskeletal). According to treatment modalities, 10 were treated with surgery alone, 11 with surgery and chemotherapy, and 7 with surgery, radiation therapy and also with chemotherapy. The primary tumor was lower than 5 cm in its dimension in 21 patients. While in 5 patients, tumor was more than 5 cm but did not exceed 10 cm, it was >10 cm in 2 patients. The c-kit expression was positive in 7 patients both cytoplasmic and membranously, whereas 8 patients were positive cytoplasmically. In 5 PNET patients, c-kit expression were stained immunohistochemically in over 50% and in 3 of ES patients. There was no significant correlation between c-kit expression and gender, localization, metastatic status, treatment modalities and tumor. Although in survival analysis, patients treated with surgery alone lived longer, while >50% of patients treated with c-kit expression lived for a shorter period.
We suggest that therapy with tyrosine kinase inhibitor for PNET and ES patients may be an alternative in addition to standard therapy modalities, especially in patients non-responsive to standard therapy.