1. ¹Pediatric Hematology Oncology, Schneider Children's Medical Center of Israel, Petah Tikva, Israel
2. ²Molecular Oncology, Felsenstein Medical Research Center, Rabin Medical Campus, Petah Tikva, Israel
3. ³Pathology Department, Sourasky Medical Center, Tel Aviv, Israel
4. ⁴Pathology Department, Rabin Medical Center, Petah Tikva, Israel
5. ⁵Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel

Correspondence: Dr S Avigad, Pediatric Hematology Oncology, Schneider Children's Medical Center of Israel, Petah Tikva 49202, Israel. E-mail: savigad@post.tau.ac.il

Deceased.

Received 18 October 2006; Revised 23 January 2007; Accepted 1 February 2007; Published online 19 March 2007.

Abstract

The significance of tumor cell contamination in marrow and peripheral blood stem cell (PBSC) collections of patients with solid tumors remains controversial. Various methods have been developed to purge tumor cells from autologous stem cell products, including CD34⁺ selection. PBSC harvests from patients with Ewing family of tumors (EFT) were analyzed for contaminating tumor cells prior and after CD34⁺ selection using reverse transcription-polymerase chain reaction (RT-PCR) and flow cytometry (FC) analyzes. The expression of CD34 was studied by RT-PCR and FC in 14 primary tumors and 13 PBSC harvests, respectively. Tumor cells were identified in the harvests by both methods. In two patients, contaminating tumor cells were evident by RT-PCR only after positive selection. FC analysis confirmed a higher level of tumor cells in the CD34⁺ fraction. In an attempt to explore this finding, expression of CD34 was detected in 93% of primary tumors and 67% of contaminated harvests. As CD34 is expressed on EFT cells, these cells may be enriched following CD34⁺ selection of harvests, although the total number of tumor cells is reduced. Other methods of purging, rather than CD34⁺ selection, should be explored in patients with EFT undergoing autologous stem cell transplantation.