S9C25bP16bNLD


S9C25bP16b-1: In this specimen, with this stain (colloidal iron), the yellow areas in the reticular dermis are zones of inflammation, both perivascular and interstitial. The yellow infiltrates, in areas, have a horizontal orientation. They are granulomatous components that tend to collect in palisaded patterns at the periphery of altered collagenous components. The perivascular components are either lymphohistiocytic or granulomatous infiltrates. The horizontal yellow components form layers at levels in the dermis, a quality that has been compared to the “layers of a cake” (colloidal iron stain: yellow= elastica and cells, red=collagen, and green=connective tissue mucin) (necrobiosis lipoidica diabeticorum: NLD).

S9C25bP16b-2: The reaction in the dermis in a lesion of necrobiosis lipoidica diabeticorum (NLD) is basically a granulomatous collagenosis. The granulomas are arranged radially about zones of altered connective tissue. In some areas, the connective tissue bundles are fibrillated and fibrin deposits are present among, and on, the connective tissue fibers (green arrows). Red arrows identify histiocytes within collagen bundles; they appear to lie within lacunae; in this location, they are ideally placed to produce lysis of the collagen bundles. In the process, basic collagen fibers and fibrils are exposed. Giant cells are the result of fusion of histiocytes; new histiocytes may be recruited into, and lose their identity in, the cellular community of each giant cell.

S9C25bP16b-3: In this field of a lesion of NLD, the distinctive features, commonly seen in all examples, include: activated histiocytes and giant cells (red arrows); collagenosis with pallor of collagen bundles; and reorientation of each bundle - of groups of like bundles - to a plane parallel to the surface of the skin. Additional features include: focal (apparent) hyperelastosis (top of field - a pattern related to a reduction in the collagenous component with collapse of the elastic component); fibrolysis affecting both the collagenous and the elastic components; and fibrin deposits in the interstitium in areas of fibrolysis (fibrillar, yellow deposits among the pale collagen bundles). Foci of necrosis are an additional feature, often in geographic patterns (the area in this field showing fibrinoid among collagen bundles is necrotic [fibrinoid necrosis]); the lack of nuclei in the zone of fibrinoid change and the fragments of nuclear debris at the interface between viable and necrotic zone offer support for an interpretation that the area is necrotic (the area could also be characterized as a zone of “necrobiosis”).

S9C25bP16b-4: Occlusive vasculopathies (in this field, a small vessel shows thrombosis) must be included in the list of features that are encountered, with variable frequency, in lesions of NLD.

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