A modal chromosome number of 55 indicates that the most common chromosome count in a particular cell population is 55 chromosomes, instead of the normal human diploid number of 46. This abnormal chromosome number suggests the presence of chromosomal aberrations or aneuploidy in the cells, which can be associated with various disorders or diseases, including cancer.

Cells with a modal chromosome number of 55 may have gained additional chromosomes or chromosomal fragments during cell division or as a result of genomic instability. These extra chromosomes can lead to changes in gene dosage and alterations in gene expression patterns, which may contribute to the development and progression of disease.

Cancer cells, in particular, are known for their chromosomal instability and can exhibit a wide range of modal chromosome numbers. In such cases, the abnormal chromosome number might provide researchers with insights into the specific type of cancer, its biology, and potential treatment strategies. However, it is important to note that not all cells with an abnormal modal chromosome number are necessarily cancerous or disease-causing, and the significance of the chromosomal aberration depends on the specific genes and genomic regions affected.