A small subgroup of human CD3-positive T-cell lymphoblastic lymphoma (T-LL) has been recently identified to express the T-cell receptor (TCR) gamma/delta heterodimer. Moreover peculiar clinical and histologic patterns of spleen and liver involvement have been associated with the TCR gamma/delta phenotype of tumor cells. In this paper we describe a human T-LL cell line (LL-DP) established in beige-nude-xid (BNX) mice, that by immunophenotype, molecular, and karyotype analyses, maintained most of the features of the patient. After serial transplants in BNX mice, LL-DP acquired quite a stable phenotype, producing a visible tumor in about 5 weeks in all the intravenously injected animals. The minimum number of transplanted cells that produce a tumor in all mice is 1 x 10(6). BNX mice bearing LL-DP lymphoma cells presented marked abdominal distension and splenomegaly. Diffuse lymphadenopathy with large tumor deposits in various lymph nodes that produce architectural effacement with a diffuse growth pattern was documented. The bone marrow was completely replaced, and spleen, liver, and kidneys were involved. Invasion of the central nervous system was leptomeningeal and perivascular. Overall this model might be useful for understanding mechanisms supporting lymphoma growth and progression as well as for testing new therapeutic strategies.