Cytogenetics of neuroblastoma: a study using fine needle aspiration cultures

Assessment of fine needle aspiration cytology samples for molecular genetic analysis in neuroblastoma

PURPOSE

To assess the utility of fine needle aspiration cytology (FNAC) samples for molecular genetic analysis of neuroblastoma.

METHODS

The case files from the pediatric solid tumor clinic were reviewed to identify 20 neuroblastoma patients whose pre-treatment FNAC slides were preserved in the cytology laboratory. The FNAC slides were destained, air dried and hybridisation with fluorescence in situ hybridisation (FISH) probes was performed as per protocol. All slides were screened and analyzed carefully under the fluorescent microscope. Over four-fold increase of the N-myc signal numbers was defined as N-myc amplification. Focal occurrence of cells (at least 50) showing N-myc amplification surrounded by non-amplified tumor cells was defined as focal N-myc amplification. Presence of three or more signals for the long arm of chromosome 17 was defined as 17q gain.

RESULTS

FISH analysis gave informative results for all the FNAC smears in our study. FISH analysis of FNAC smears showed N-myc amplification in 5 (25 %) out of 20 patients and 15 (75 %) showed normal N-myc copy number. Three out of these five patients had homogenous amplification and two patients had focal N-myc amplification, indicating tumor heterogeneity. On investigation of chromosome 17q status, 5 (25 %) out of 20 patients demonstrated gain of 17q and 15 (75 %) patients showed normal 17q status. Four out of the five patients with 17q gain also showed N-myc amplification.

CONCLUSIONS

The current study indicates that FNAC is a rapid and atraumatic diagnostic method for neuroblastoma which provides sufficient material for molecular genetic analyses by means of FISH.

Cytogenetic evaluation of neuroblastoma using fine needle aspiration cultures

PURPOSE

Open surgical biopsies of the primary tumor and bone marrow sampling in metastatic disease are the major sources of tumor material for genetic studies in neuroblastoma. The possibility of using cultures of material procured through Fine Needle Aspiration (FNA) for upfront cytogenetic studies of neuroblastomas is studied.

METHODS

From January 2006 to April 2008, 18 patients were diagnosed as neuroblastoma on fine needle aspiration cytology (FNAC). FNA material was cultured and processed to obtain metaphases and chromosomal analysis was performed. Minimum of five selected metaphases were analyzed and changes were documented.

RESULTS

The diagnosis of neuroblastoma was confirmed by FNAC in all. Among the 18 cases, 9 cases (50%) showed metaphases on cultures. Four cultures did not grow and five cultures got contaminated. Out of the nine cases that showed metaphases, four cases showed cytogenetic abnormalities. Near triploidy and Double minutes (Dmins) were seen in one case and tetraploidy in another case. 1q gain and 2q gain were observed respectively in third and fourth cases.

CONCLUSION

FNA provides viable single cell suspension suitable for cultures. This may be a good alternative strategy to acquire material for cytogenetic studies in neuroblastoma.

Distinct evolutionary mechanisms for genomic imbalances in high-risk and low-risk neuroblastomas

BACKGROUND

Neuroblastoma (NB) is the most common extracranial solid tumour of childhood. Several genomic imbalances correlate to prognosis in NB, with structural rearrangements, including gene amplification, in a near-diploid setting typically signifying high-risk tumours and numerical changes in a near-triploid setting signifying low-risk tumours. Little is known about the temporal sequence in which these imbalances occur during the carcinogenic process.

METHODS

We have reconstructed the appearance of cytogenetic imbalances in 270 NBs by first grouping tumours and imbalances through principal component analysis and then using the number of imbalances in each tumour as an indicator of evolutionary progression.

RESULTS

Tumours clustered in four sub-groups, dominated respectively by (1) gene amplification in double minute chromosomes and few other aberrations, (2) gene amplification and loss of 1p sequences, (3) loss of 1p and other structural aberrations including gain of 17q, and (4) whole-chromosome gains and losses. Temporal analysis showed that the structural changes in groups 1-3 were acquired in a step-wise fashion, with loss of 1p sequences and the emergence of double minute chromosomes as the earliest cytogenetic events. In contrast, the gains and losses of whole chromosomes in group 4 occurred through multiple simultaneous events leading to a near-triploid chromosome number.

CONCLUSION

The finding of different temporal patterns for the acquisition of genomic imbalances in high-risk and low-risk NBs lends strong support to the hypothesis that these tumours are biologically diverse entities, evolving through distinct genetic mechanisms.

Characterization of karyotypic events and evolution in neuroblastoma

BACKGROUND

Neuroblastoma (NB) is cytogenetically characterized by a number of non-random events. However, knowledge is limited concerning the timing of occurrence and inter-action of many of these events.

METHODS

Karyotypic patterns were obtained from a study group of 49 NB tumors that had been analyzed by conventional cytogenetics combined with FISH and in some instances SKY.

RESULTS

All chromosomes were involved in a numerical and structural aberration in at least one tumor. There was a positive correlation between the occurrence of MYCN and del(1p) and between del(1p) and 17q. Aberrations involving chromosomes X, 3, 19, and del(1p) could be considered early events, whereas those involving chromosomes 9, 13, 15, 18, 20, and 21 were often late events.

CONCLUSIONS

This study suggests that the karyotypic patterns characterizing NB are complex. There are aberrations that can be grouped into early or late karyotypic events, but others, such as gain of 17q, are variable.

Fine-needle aspiration of adult small-round-cell tumors studied with flow cytometry

Immunophenotypic study is critical for the diagnosis of adult small-round-cell tumors (SRCTs). We describe three patients with Ewing's sarcoma/primitive neuroectodermal tumor (ES/PNET) and one patient with neuroblastoma in which flow cytometry immunophenotyping (FCI) on the fine-needle aspirate (FNA) and bone marrow aspirate (BMA) demonstrated an abnormal population of cells that were CD45(-) and CD16/CD56(+). Four patients with mean age of 30 years, three male and one female, clinically suspicious for a lymphoma or SRCT are described. FNA, BMA, and biopsy specimens were obtained for routine cytologic and histologic evaluation. Fresh tissue was studied by FCI. In all cases, the cytology smears showed small cells with round nuclei, slightly irregular nuclear membranes, fine chromatin, and scant cytoplasm. FCI showed CD16/56(+) and CD45(-) neoplastic cells in all cases. In one case, 76% of these cells were CD99(+). The diagnoses of ES/PNET were confirmed by immunohistochemical, ultrastructural, and cytogenetic studies. ES/PNET in FNA and BMA can be efficiently and rapidly diagnosed by combining cytologic examination with FCI using a panel including CD45, CD16/56, and CD99.