Background There has been continuous debate as to whether Y chromosome loss is an age related phenomenon or acytogenetic marker indicating a malignant change.This study aimed to investigate the frequency of Y chromosome lossin the specific patients in order to determine whether it is an age related phenomena or a cytogenetic marker indicating amalignant change.Methods Five hundred and ninety-two male patients with a median age of 59 years old(22-95 years)were included inthis study.These patients were divided into two groups:the study group,including 237 patients who had hematologicaldisorders included myeloproliferative disorder(MPD),myelodysplastic syndrome(MDS),acute myeloid leukemia(AML),chronic myeloid leukemia(CML),multiple myeloma(MM),and lymphoma and the control group including 355 patientswith no evidence of hematological disease.Both conventional cytogenetics and fluorescence in situ hybridization usingDNA probes specific for the centromere of chromosomes X or Y were performed according to our standard laboratoryprotocols.Results Twenty-four out of 237 patients with hematological disorders(10.1%)had Y chromosome loss.Of these 24patients,2 patients had AML(5.0% of all AML patients),2 patients had CML(5.7% of all CML patients),2 patients hadMPD(8.0% of all MPD patients),3 patients had MM(10.0% of all MM patients),5 patients had lymphoma(10.6% of alllymphoma patients)and 10 patients had MDS(16.7% of all MDS patients).Twenty-one out of these 24 patients had aloss of Y chromosome as the sole anomaly and the remaining three had a loss of Y chromosome accompanied with otherstructural changes detected by conventional cytogenetic analysis.Fluorescence in situ hybridization(FISH)analysisconfirmed the routine cytogenetic results.All 24 patients had a loss of Y chromosome with a range of 17.5%-98.5% ofcells.Two of the patients,one with AML and another with CML,had karyotype and FISH testing done both at the initialdiagnosis and during remission.The results showed a loss of Y chromosome at initial diagnosis but a normal 46,XYkaryotype during remission.Only 9 out of 355 patients(2.5%)without evidence of hematological disease had Ychromosome loss,among them 7 patients had cardiovascular diseases and 2 patients had kidney diseases.Comparisonof the incidence of Y chromosome loss in patients with hematological disorders or without evidence of hematologicaldisease using statistical analysis showed a statistically significance difference(P<0.05).Conclusions The present study demonstrated that the frequency of Y chromosome loss is significantly higher inpatients with hematological disorders than in patients without hematological disorders,which indicates that the loss of Ychromosome is associated with a neoplastic change. Background There has been continuous debate as to whether Y chromosome loss is an age related phenomenon or acytogenetic marker indicating a malignant change. This study aimed to investigate the frequency of Y chromosome lossin the specific patients in order to determine whether it is an age related phenomena or a cytogenetic marker indicating amalignant change. Methods Five hundred and ninety-two male patients with a median age of 59 years old (22-95 years) were included in the study. These patients were divided into two groups: the study group, including 237 patients who had hematologicaldisorders included myeloproliferative disorder (MPD), myelodysplastic syndrome (MDS), acute myeloid leukemia (AML), chronic myeloid leukemia (CML), multiple myeloma (MM), and lymphoma and the control group including 355 patients with no evidence of hematological disease.Both conventional cytogenetics and fluorescence in situ hybridization using DNA probes specific for the centromere of chromosomes X or Y were performed Two out of 237 patients with hematological disorders (10.1%) had Y chromosome loss. Of these 24 patients, 2 patients had AML (5.0% of all AML patients), 2 patients had CML (5.7% Of all CML patients, 2 patients hadMPD (8.0% of all MPD patients), 3 patients had MM (10.0% of all MM patients), 5 patients had lymphoma (10.6% of alllymphoma patients) and 10 patients had MDS (16.7% of all MDS patients. Twenty-one out of 24 patients had aloss of Y chromosome as the sole anomaly and the remaining three had a loss of Y chromosome accompanied with other structural changes detected by conventional cytogenetic analysis. Fluorescence in situ hybridization (FISH) analysisconfirmed the routine cytogenetic results. All 24 patients had a loss of Y chromosome with a range of 17.5% -98.5% of cells. Two of the patients, one with AML and another with CML, had karyotype and FISH testing done both at the initial diagnosis and during remission.The results showed a loss of Y chromosome at initial diagnosis but a normal 46, XYkaryotype during remission. Ofly 9 out of 355 patients (2.5%) without evidence of hematological disease had Ychromosome loss, among them 7 patients had cardiovascular diseases and 2 patients had kidney diseases.Comparisonof the incidence of Y chromosome loss in patients with hematological disorders or without evidence of hematological disease using statistical analysis showed averaging significance difference (P <0.05). Conclusions The present study demonstrated that the frequency of Y chromosome loss is significantly higher in patients with hematological disorders than in patients without hematological disorders, which indicates that the loss of Ychromosomes is associated with a neoplastic change.