S10C3P1-2: Near the top of the field, a distinctive lesion is represented in an edematous fibrous septum. An angulated defect is surrounded by palisades of immature histiocytes; this distinctive lesion is found in the setting of some examples of erythema nodosum (a feature seen in some examples, presumably lesions which are early in their evolution). The characterization of this distinctive “granuloma” has been attributed to Miescher. A few neutrophils are present in the interstitial infiltrates, but the preponderant cells are histiocytes.

S10C3P1-3: This is an example of a chronic septal panniculitis; the lesion has granulomatous qualities of a more ordinary type. The septum is widened, edematous, and fibrotic; it shows hyperplasia of mesenchymal cells. Granulation tissue extends, in substitutive patterns, from the altered septum into the domain of the lobules of adipose tissue; the granulation tissue maintains a septal base. In this field, clusters of epithelioid histiocytes and multinucleated giant cells are present in the granulation tissue (subacute migratory panniculitis; granulomatous septal panniculitis; chronic erythema nodosum).

S10C3P1-4: This is another example of a septal panniculitis in the category of subacute migratory panniculitis. The septum is centrally located; it is widened and fibrotic. Granulation tissue, which is septum-based, extends into the neighboring lobules of adipose tissue. In both the septum and the granulation tissue, granulomas, some of which are associated with multinucleated giant cells, are scattered. There are spotty infiltrates of lymphoid cells.