T-cell malignancies are rare, making up 10% to 15% of all lymphoid neoplasms in 
adults. They include many different types of disorders such as T-cell 
prolymphocytic leukemia, T-cell large granular lymphocytic leukemia, adult 
T-cell leukemia/lymphoma, cutaneous T-cell lymphoma, and peripheral T-cell 
lymphoma, which are themselves divided into multiple subcategories. Most T-cell 
malignancies arise as a result of chromosomal abnormalities, including T-cell 
receptor rearrangement anomalies. Viral infections are implicated in the 
development of adult T-cell leukemia/lymphoma and some cases of peripheral 
T-cell lymphoma have been linked to Epstein-Barr virus or human immunodeficiency 
virus infection. With the possible exception of T-cell large granular 
lymphocytic leukemia, which often has an indolent course, T-cell malignancies 
have not responded well to conventional chemotherapeutic treatment. The 
introduction of monoclonal antibodies for the treatment of cancer has changed 
the outlook for patients with T-cell malignancies. Recent studies with 
single-agent alemtuzumab, an anti-CD52 monoclonal antibody, have shown improved 
response rates and survival in patients with T-cell prolymphocytic leukemia and 
cutaneous T-cell lymphoma. Preliminary data also suggest that alemtuzumab may 
have activity in patients with heavily pretreated peripheral T-cell lymphoma who 
are refractory to conventional chemotherapy. Preclinical studies with mice 
bearing human adult T-cell leukemia/lymphoma cells suggest that alemtuzumab may 
have a potential therapeutic role in this setting. Treatment of T-cell 
hematologic malignancies with alemtuzumab appears promising. Earlier treatment 
and combination with chemotherapeutic agents may improve treatment outcome for 
patients with these malignancies and allow for consolidation with stem cell 
transplant strategies in selected patients.