S3C21aP9a-Hypertrophic Lichen Planus

S3C21aP9a-1: This is a variation on the theme of hypertrophic lichen planus. The rete patterns are irregular; some of the rete ridges are elongated and thin with pointed extremities (saw-toothing). Focally, the rete ridges are effaced. The epidermis shows compact hyperkeratosis, a prominent granular layer, and hyperplasia of the superficial unit (with hypertrophy of the cells of the superficial unit). The keratinocytes of the altered superficial unit are individually enlarged. They show increased cytoplasmic acidophilia. The widened papillary dermis is fibrotic. Perivascular infiltrates of chronic inflammatory cells are prominent in the widened papillary dermis, but do not extend along the vessels into the reticular dermis. There are liquefactive changes at the dermal-epidermal interface with scattered lytic defects.

S3C21aP9a-1: At a higher magnification, there is liquefaction degeneration at the dermal-epidermal interface. Loose lymphoid infiltrates hug the epidermis in the area outlined by blue arrows. This localized area evokes images of hypertrophic lichen planus. The other collections of images then take on the qualities of secondary changes.

S3C21aP9a-2: The rete ridge to the right of the center of the field shows well-developed lichenoid patterns of lichen planus-like type. The widened papilla to the left of this rete ridge contains a cluster of dilated vessels; the pattern in this area has the qualities of angiodermatitis. Angiodermatitis is a common feature of the papillary dermis in association with inflammatory (and neoplastic) disorders on the lower extremities. Just beyond the extremities of the rete ridges, coarse, acidophilic, fibrous lamellae form a plate-like lattice; This material is unusually coarse in this lesion of lichen planus, but might represent reduplicated basement membrane material.

S3C21aP9a-3: The lytic defects at the extremity of the rete ridge contains lymphocytes, histiocytes (including melanophages), and occasional necrotic keratinocytes. All the keratinocytes, above the defect, have acquired characteristics of keratinocytes showing terminal differentiation. This is a characteristic alteration of the epidermis in lichen planus-like disorders. Distinctive “fibrous” lamellae are represented in the dermis beneath the altered rete ridge; they are interconnected to form a lattice. Some of the material extends to the margin of the epidermal defect; it outlines the defect in basement membrane-like fashion. Reduplication of basement membrane material is common in lesion of lichen planus, but it is most unusual to see it in this exaggerated pattern, if the material is truly altered basement membrane.

S3C21aP9a-4: This is a hypertrophic lichenoid dermatitis. Several collection of virtual images have application for the interpretation of the patterns. One collection of images relate to the patterns of fibrosis in the papillary dermis; the vertically oriented, fibrous lamellae evokes the images of lichen simplex chronicus. The lobular aggregates of tortuous thick walled vessels in the widened, fibrotic papillary dermis evoke images of angiodermatitis. The altered rete ridges with pointed extremities evoke images of erosive effects of a lichen planus-like reaction. The epidermis has taken on the qualities of a hyperplastic superficial unit. Hypertrophic lichen planus is common on the lower extremities.

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