A study of consecutive bone marrow aspirates from 365 patients without lymphoproliferative disorder, ten patients with chronic lymphocytic leukemia (CLL), and 25 patients with malignant lymphoma disclosed a clear separation of normal from abnormal lymphoid nodules (LN). Normal LN were found in 47% of patients and were classified into lymphoid follicles and lymphoid infiltrates. A new entity, nodular lymphoid hyperplasia (NLH), was diagnosed on ten bone marrows which contained a low-power field displaying four or more lymphoid nodules or showed a lymphoid nodule larger than 0.6 mm. The clinical significance of nodular lymphoid hyperplasia remains unknown; in certain cases it represents a precursor state of a mature lymphocytic lymphoproliferative disorder. Nodular aggregates in CLL are of the infiltrate type and exhibit a tendency to confluence. Eleven of the 25 patients with malignant lymphoma displayed lymphoreticular nodules which were cytologically similar to the original lymphoma and different from normal LN. Two patients, one with reticulum cell sarcoma and one with Hodgkin’s disease, showed NLH of the bone marrow. Bone marrow LN in patients with an established diagnosis of mature lymphocytic lymphoma have to be interpreted with the utmost caution. Confluence of LN, irregular shapes, and the presence of prolymphocytes and lymphoblasts speak for lymphomatous nodules. Additional clinicopathologic studies are necessary to sharpen the distinction between NLH and well-differentiated lymphoproliferative disorders.

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