1. A description of the cells of normal lymph nodes is presented, based on the examination and differential counts of smears from 15 nodes obtained at operation.
2. 95 per cent of the cells of normal nodes are lymphocytes. The most primitive cell is the multipotent hemohistioblast which gives rise to the histiocyte and the hemocytoblast the parent of three differentiated 'blast cells, the lymphoblast, monoblast and plasmoblast. 'Blast cells are rare in normal nodes but can be observed in inflammation.
3. The cytology of 85 pathologic nodes is described, the final diagnoses being confirmed histologically in most instances.
4. The features of inflammation are similar irrespective of the cause. Some types of inflammation result in excess of one series of cells more than another; it is rarely possible to distinguish them on these grounds, but the cytology may indicate those cases in which search for tubercle bacilli is likely to be rewarding.
5. Sternberg cells and their precursors are almost specific for Hodgkin’s disease. Diagnosis is possible if they are present together with a pleomorphic cytology.
6. A diagnosis of leukosis or primary or secondary neoplasm can be made if 80 per cent of the cells are abnormal. Distinction of these three groups from smears depends on the type and distribution of cells. The degree of abnormality bears no relation to prognosis.
7. Diagnosis depends on finding abnormal cells; differential counts are of little value.
8. Analysis of the few cases of reticulosis examined suggest that cytologic classification is unlikely to be useful.
9. Examination of one smear from each of 85 nodes for 15 minutes without clinical information enabled a diagnosis to be in 52 cases; the only error was that monocytic leukosis was called reticulosarcoma.
10. On two occasions, one of secondary carcinoma and one of reticulosis, the correct diagnosis was made from smears at a time when histology showed nonspecific changes only.
11. The method should find a useful place as a screening test in diagnosis of lymphadenopathy, excision of a node being carried out if aspiration fails or if the diagnosis cannot be made from smears.