Lymphoproliferative disorders: Molecular diagnostics

The challenges of diagnosing lymphoproliferative disorders in immunodeficiency syndromes are several. Epstein-Barr virus (EBV) causes proliferation and transforms cells; therefore, it is thought to allow greater chances for random molecular events to occur above the baseline expected for the patient's age. T-cell immunosuppression contributes to the allowance of proliferation. Due to the immune deficiencies, patients are at variable risk throughout their lives for lymphoproliferations, whether hereditary or subsequent to an acquired immune deficiency such as transplantation, human immunodeficiency virus (HIV) infection or in other diseases where induced immune suppression occurs secondary to steroid or methotrexate treatment. Determining whether the proliferation is a hyperplasia or a lymphoma is difficult because both events, or rather a spectrum of events, can occur in such patients. Therefore, while an EBV-positive atypical lymphoid hyperplasia can occur at one site, a clonal neoplasm may occur at another site in the same patient. The lymphoproliferations are often polymorphous, at least initially, and then develop a monomorphous histology similar to a typical lymphoma. However, the histology is not easily predictive of when a committed clonal translocation develops; therefore, multiple modalities are needed to aid in the establishment of a lymphoma. This is important to separate it from the differential diagnosis of infectious mononucleosis or an EBV-positive lymphoproliferation that mimics infectious mononucleosis.