Primary plasma cell leukaemia: immunological and ultrastructural studies in 6 cases.

The clinical and laboratory studies of 6 patients with primary plasma cell leukaemia are described. The leukaemic cells had a variable morphology, ranging from lymphoplasmacytic and mature plasma cells to poorly differentiated blasts. The neoplastic plasma cells had a characteristic phenotype: they were positive for CyIg and the McAb OKT10 and Ri-3, and did not express the B-cell antigens Ia, B1 and B4. Ultrastructural studies confirmed the plasma cell nature of the leukaemic cells and showed the presence of a meshwork of cytoplasmic fibrils in 50 to 90% of the neoplastic cells from all cases. The distinct ultrastructural and immunological features of PCL described in this study will help the diagnosis and further characterisation of this disease entity.