S9C26P17NLD



S9C26P17-1: This is a characteristic pattern for the changes in the superficial portion of the dermis in a lesion of necrobiosis lipoidica. In this example, the epidermis shows basal unit hyperplasia in psoriasiform patterns. Focally, the superficial unit, particularly to the left, is hyperplastic in patterns of terminal differentiation. The papillary dermis and a thin superficial zone of the reticular dermis are relatively uninvolved. There are prominent perivascular infiltrates of lymphoid cells in the reticular dermis; they extend along vessels to the deep margin of the field. In addition the infiltrates are band-like (interstitial) in the upper portion of the reticular dermis. The infiltrates form a boundary at the interface between relatively uninvolved dermis and markedly altered dermis. Beneath the band-like zone of inflammation, collagen bundles are swollen; they are parallel to each other and to the surface of the skin. This altered connective tissue is relatively acellular. It is sclerotic in a most distinctive manner, but the orientation of the collagen bundles is not diagnostic (see pictorials of morphea). In the reticular dermis of a lesion of NLD, the prominent interstitial and perivascular infiltrates seem to form layers at levels in the dermis; this pattern has been compared to layers of a cake. Lesions of NLD classically are pandermal in the reticular dermis; they extend to the margins of biopsies and to the deep margin of the dermis. They may involve septa of the subcutaneous fat and creep into the adipose in the pattern of substitutive fibrosis (morphea-like qualities).

S9C26P17-2: At a higher magnification, the inflammatory infiltrates of this lesion of necrobiosis lipoidica (NLD) outline zones that are hypocellular, or even focally acellular, especially on the right (i.e., necrobiosis). Collagen bundles in the altered areas are streaked in a direction that parallels the surface of the skin. This is the fibrotic phase of NLD; it is a form of substitutive, or interstitial, fibrosis.

S9C26P17-3: At still higher magnification, the band-like infiltrates near the interface between the papillary dermis and the reticular dermis are composed of lymphocytes and epithelioid histiocytes in granulomatous (and palisaded) patterns. The perivascular components are lymphoid. Above the band-like infiltrates, the dermis shows some alterations in the size and direction of collagen bundles, but the patterns are less distorted than those in the acellular area below the granulomatous zone. In the acellular area, the collagen bundles are swollen; they vary in the intensity of their affinity for eosin stain. Some bundles are bright red, but many of the neighboring bundles are pale. The paucity of nuclei in the altered fibrous tissue is a feature of a zone of necrosis. The preservation of the collagen bundles in a recognizable pattern suggests that the necrosis may have been mediated at a vascular level (the patterns are infarct-like). The persistence of this necrotic fibrous tissue in the face of a granulomatous response suggests that there is, in the altered zone, a factor which impairs the enzymatic functions of histiocytes. This persistence of a zone of “necrosis” (without evidence of lysis and organization) might be offered as evidence in support of the common characterization of the pattern as “necrobiosis” (i.e., the surrounding tissue is alive but the zones of necrosis are persistent), or as a “gummatous” infarct. The area of necrosis to the left is “geographic,” both in outline and, in the company of other similar zones, in distribution.

S9C26P17-4: With a Verhoeff-van Giesen stain, there are three zones in the field. To the left and below, the collagen bundles are red and thin. Elastica is well-preserved; the elastic fibers are regularly spaced.

To the right and above, the collgen bundles are swollen; spaces among the bundles vary in size and outline. Elastica is not represented (elastolysis is complete). A border zone is triangular with the apex directed down and to the right. In it, the collagen bundles are swollen and yellow. Elastica is represented in greater amounts than on the far right, and in lesser amounts than on the far left (a transition zone showing elastolysis in progress).

This is a well-developed lesion with alterations in both the elastic and collagenous components. Between the blue arrows, a packet of thin collagen bundles, in parallel arrays, is represented.

S9C26P17-5: In this area of a lesion of NLD, there is a central area showing partial fibrolysis of collagen bundles and elastic fibers. The periphery of the zone of partial fibrolysis is outlined by swollen, yellow (necrobiotic) collagen bundles, especially to the right, and left. At the interface between the zone of sclerosis and zone of fibrolysis, some of the coarse collagen bundles are longitudinally fissured; the individual segments can be traced into the zone of fibrolysis. The changes in this old lesion are compatible with a zone of sclerosis in which the zone of more extensive fibrolysis is a recent event. The damage in this area is chronic, but repetitive. Vascularized fibrous tissue has invaded the sclerotic tissue (boundary marked by green arrows). Thin, new bundles of the vascularized tissue are red (red arrows).

S9C26P17-6: On the right side of the field, the dermis is edematous and hyalinized (NLD). Histiocytes and giant cells are loosely spaced to the left and at the margin of the hyalinized matrix. There are traceries of elongated cells (histiocytes). Sinuous processes of the histiocytic giant cells extend into the hyalin (blue arrows). At the periphery of the zone of altered fibrous tissue, the histiocytic assault on fibrous components remains active.

S9C26P17-7: On the right, a tangentially oriented column of squamous cells partitions the field into two distinct zones. Above, there is a zone of loose fibrous tissue in which the collagen bundles are thin and parallel; the fibrous tissue is loosely, but regularly, cellular. At its extremity, this column of squamous cells has a claw-shaped configuration (a configuration commonly encountered in examples of pseudoepitheliomatous hyperplasia in the setting of the perforationg disorders). In fact, the deep surface of the column is gently scalloped at its interface with the altered fibrous matrix in the lower portion of the field. The altered matrix below the column of squamous cells is acellular; its collagen bundles are pale and swollen. The zone has the qualities of an infarct, but retains its general structure. This preservation of an “infarct” (necrobiotic or gummatous area) in a zone of viable, but altered, tissue qualifies as “necrobiosis.” The changes at the extremity of the column are compatible with impending perforation. The vertically oriented column to the left is a follicle; the follicle terminates at the level where it contacts the necrotic dermis; by the characteristics of the follicular epithelium, this follicle is permanently stunted.

S9C26P17-8: The changes in this area of a young lesion of NLD qualify as a granulomatous collagenosis. Histiocytes form traceries among collagen bundles. The collagen bundles are reduced in size; some are perculiarly angulated. Spaces among the bundles are accentuated. In the region outlined by blue arrows, histiocytes, showing prominent cytoplasmic processes, are clustered about a defect (a defect presumably produced by the digestion of collagen in response to the release of the enzymes by histiocytes; the process is fibrolytic).

S9C26P17-9: Plasma cells generally are a feature of the perivascular infiltrates in NLD. In this field, they are prominent in the perivascular infiltrates of the subcutaneous tissue near the lower margin of the dermis (red arrows).

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