Nodal B-cell lymphomas in Japan--particularly in Tohoku district.

There are different frequencies in the immunological phenotypes of malignant lymphomas in Tohoku and Kyushu districts of Japan. In the Tohoku district, the northern area of Honshu, B-cell lymphomas are more preponderant than T-cell lymphomas. This is just the reverse on the islands of Kyushu and Shikoku. Histologically diffuse lymphoma of large cell type, formerly termed reticulum cell sarcoma or histiocytic lymphoma, was the most frequent (48%) among B-cell lymphomas. It is characteristic of B-cell lymphoma that immunoglobulin is produced in either or both the cellular surface and cytoplasm. Cytoplasmic IgM in lymphoma cells was mainly detected by an electron microscopic enzyme-labeled method. Cytoplasmic-Ig was present both in the nuclear membrane and endoplasmic reticulum. This technique is particularly useful in medium-sized lymphoma cells because of the scanty cytoplasmic rim making light microscopic evaluation difficult. Histological transition from follicular to diffuse pattern is characterized by a change of cellular arrangement from labyrinth-like cellular connections in follicular lymphoma to more simple connections in diffuse lymphoma. The transition is also supported by the fact that a higher deoxyribonucleic acid content is observed in large cells than medium-sized cells in follicular lymphoma. The data also supports the hypothesis that a diffuse lymphoma evolved from follicular lymphoma mainly occurs in cases of large cell lymphomas.