T–cell lymphoma is a type of cancer developed from it's own altered T-lymphocytes. Types of T–cell lymphoma are difficult to differentiate unless they are classified using multiple properties, e.g. differences in morphological structure of the affected tissue, immunophenotype and histochemical differences. Disrupted regulatory mechanism of VDJ genes recombination is probably one of the first and major causes of the T–cell lymphoma development. In rare cases the cause is the occurrence of a functional triplet, which brings in higher variability of the TCR, instead of a non-functional triplet or a stop codon. T–cell lymphoma is most often characterised by translocations, but it can be also developed by deletion or genome mutation resulting in changed expression of the panT antigen. These kind of cells are non-functional and if a programmed cellular death does not happen, the T–cell lymphomas develop. It is considered that viruses, e.g. EBV, HTLV1 and HIV have significant influence on the T–cell lymphoma formation. A correlation between the frequency of T–cell lymphoma appearance and geographic location is also perceived. Considering black, white and Asian races, T–cell lymphoma types have different occurrence that is linked to genetic similarities within a particular race as well as to differences between those races.