Subcutaneous nodules of Still's disease.

The observations of Collins (1937) and of Bennett, Zeller, and Bauer (1940) established clearly the pathological differentiation of the ordinary subcutaneous nodules in rheumatic fever and in rheumatoid arthritis. In brief, the rheumatic fever nodule is characterized by much fibrinoid material arranged in a lattice with apparently clear spaces between the strands, considerable oedema, but relatively little cellularity. What cells are present are usually fibroblasts or histiocytes; they are sparsely distributed in the meshes of oedematous connective tissue and accompanied occasionally by lymphocytes or rarely by polymorphs near the vascular "islands" (Fig. 1, opposite). There is little attempt at zoning, although vascular "islands" are a prominent feature. Finally, fibrosis is not often a conspicuous feature, and may be entirely absent. In contrast, the rheumatoid nodule, as seen in adults, is clearly arranged in three zones. There is an outer zone of fibrosis with considerable infiltration by lymphocytes, plasma cells, sometimes polymorphonuclears, and rarely eosinophils. The innermost zone comprises necrotic debris, sometimes containing fibrinoid material but more usually a grumous granular mass with fibrin, fibrinoid, and swollen collagen fibres mixed in it, sometimes containing nuclear debris, fat globules, and cholesterol clefts. Between the inner and outer zones lies a well-orientated layer of palisade cells, fibroblasts with large nuclei forming a compact border to the necrotic centre zone (Fig. 2, opposite). While there is some overlap in their individual features, a correct histological diagnosis can be made in nearly every case (Bennett and others, 1940, give a figure of 68 correct diagnoses in 69 patients with a firm diagnosis and one wrong diagnosis in a patient in whom the clinical diagnosis was somewhat doubtful). The exceptions show a mixed picture which gives the pathologist difficulty and leads him to issue an uncertain report. This usually corresponds to