A Case of Lymphoblastic Lymphoma with Pre-B Cell Phenotype

Naoya Nakamura, MD, Department of Pathology, Fukushima Medical College, 1 Hikarigaoka, Fukushima 960-12 (Japan) Lymphoblastic lymphoma usually shows a T cell phenotype [1], but rarely some lymphoblastic lymphoma shows a pre-B cell phenotype. We present an uncommon case of lymphoblastic lymphoma expressing a pre-B cell phenotype and review the literture. An 11-year-old Japanese boy complained of right cervical and bilateral inguinal lymphadenopathy in April 1986. Hepatosplenomegaly was not found. A surgical specimen obtained from the right cervical lymph node showed malignant lymphoma, lymphoblastic type. A chest X ray and computed tomographic scan of the thorax and abdomen revealed no abnormal finding. A hemogram of peripheral blood did not show leukemic picture. Bone marrow aspiration showed normocellularity with no leukemic cell. The patient received a combination chemotherapy and prophylactic cranial irradiation (2,400 rad), and went into complete remission. He is now receiving maintenance chemotherapy. Microscopically, normal architecture of the cervical lymph node was almost effaced by a diffuse infiltration of atypical lymphoid cells consistent with lym-phoblasts, although a few atrophic follicles were observed. The neoplastic cells had convoluted nuclei with dusty chromatin and small prominent nucleoli, and scanty basophilic cytoplasm. Electron microscopy revealed that the neoplastic cells had indented or convoluted nuclei with small prominent nucleoli. The chromatin was evenly distributed in the nucleus with peripheral condensation of heterochromatin along the nuclear membrane. The cytoplasm possessed numerous ribosomes and polyribosomes, several mitochondria and a few short rough endoplasmic cister-nae. The neoplastic cells reacted with anti-HLA-DR, anti-CD19(B4), and antiCDlO(CALLA), but not with anti-CD20(Bl), anti-CD21(B2), anti-T-cell-associated antigens and anti-myeloid-associated antigens. The neoplastic cells did not express any surface immunoglobulins. Immunoelectron microscopy demonstrated that the neoplastic cells bored the cytoplasmic μ-chain (fig. 1.). In addition, the neoplastic cells were positive for TdT activity. These findings indicate that the present case represents a neoplastic counterpart of pre-B cell. Non-T ALL with a pre-B cell phenotype is not uncommon. However, pre-B cell lymphoblastic lymphoma without leukemic blood picture is very rare; to our knowledge several cases have been reported [2–7] (table 1). These reported cases displayed the common characteristics of indented or convoluted nuclei as well as the preferential involvement of skin and lymph nodes. In addition, these cases often showed lytic bone lesions. The present case is somewhat different