Background : It has recently been shown that t (12;21) (p13;q 22) is the most common molecular genetic abnormality in childhood acute lymphoblastic leukemia (ALL). We have analyzed this translocation in an attempt to evaluate its incidence and to monitor minimal residual disease (MRD) with t (12; 21) rearrangement by detection of TEL-AML1 transcript in patients with childhood ALL. Procedure : All cryopreserved bone marrow samples were analyzed using a nested reverse transcriptionpolymerase chain reaction (RT-PCR) method. TEL-AML1 transcripts were searched for in 34 ALL patients, including six in relapse consecutively diagnosed at our institution between 1991 and 1997. Results : TEL-AML1 transcripts were found in five (19%) of 27 patients with B precursor ALL. The patients with BCR-ABL , chromosome 11q23 rearrangement and T-ALL patients did not express TEL-AML1 transcripts. Moreover, MRD in five patients with TEL-AML1 transcripts were analyzed in serial samples. Although TEL-AML1 transcripts disappeared soon after the beginning of chemotherapy in three of the five patients, one patient continued to express them for up to 21 months without recurrence and remained in continuous complete remission for seven years after the cessation of chemotherapy. The remaining patient was admitted to our hospital after the second relapse but died following a failure to induce complete remission. Conclusion : For most patients, the presence of TEL-AML1 transcripts suggests excellent chemosensitivity and a favorable prognosis, but some patients with these transcripts have a different outcome. The present study suggests the possibility that a persistence of MRD is not necessarily related to a relapse of ALL with TEL-AML1 fusion. The prognostic significance of TEL-AML1 transcript remains controversial. Further studies are needed to evaluate the relation between the TEL-AML1 transcript and prognosis.

RT-PCR for TH mRNA might be the most sensitive method for the detection of occult neuroblastoma cells in BM and PB. However, because invasion of the BM by neuroblastoma may have a focal distribution, sampling errors can occur. Therefore, not only RT-PCR but also MRI, need to be used to rule out marrow involvement, especially at diagnosis and BM relapse.

BACKGROUND In the current study, the authors report a 4 year old girl with disseminated retinoblastoma. To find sensitive and specific molecular markers for detection of retinoblastoma cells in blood and marrow, the authors evaluated three photoreceptor‐associated gene transcripts by using reverse transcription polymerase chain reaction (RT‐PCR). METHOD Samples of bone marrow and blood were obtained from healthy donors and the patient. RT‐PCR was performed to detect the cone α′‐subunit of cGMP phosphodiesterase (cone α′‐PDE), the rod β‐subunit of cGMP (rod β‐PDE), and the interphotoreceptor retinoid‐binding protein (IRBP) gene transcript in RNA extracted from the samples. RESULTS While no expression of rod β‐PDE or IRBP was detected in any of the normal samples, expression of cone α′‐PDE was detected in two out of seven normal marrow samples. Expression of rod β‐PDE was not detected in the patient samples. Expression of IRBP was detected in the patient samples obtained from iliac bone marrow before intensive chemotherapy but not thereafter. CONCLUSION RT‐PCR for IRBP was a useful method for detecting metastatic retinoblastoma cells as well as for evaluating the therapeutic effects of treatment in this particular case. Cancer 2001;91:1568–73. © 2001 American Cancer Society.