S13C13aP11AXeroderma



S13C13aP11a-1: The patterns are those of a cell-poor lichenoid reaction (LE-like pattern). Centrally, there is liquefaction degeneration at the dermal-epidermal interface. In this area, the epidermis shows a shift to the patterns of terminal differentiation with a loss of a defined basal unit; the superficial unit is hyperplastic. The dermis shows fibrosis and telangiectasia (7 year old boy, xeroderma pigmentosa).

S13C13aP11a-2: Over most of the dermis, the patterns, in the epidermis, are those of a cell-poor lichenoid dermatitis. The superficial unit is hyperplastic and is acidophilic with a prominent granular layer. Near the right margin, there is a change in the character of the epidermis. A basal unit is well-defined; the epidermal patterns are more normal at this margin. The dermis at the interface with the epidermis is fibrotic; it shows hyperplasia of connective tissue cells. There are perivascular infiltrates of lymphoid cells.

S13C13aP11a-3: Yellow arrows define an interface with “clonal” qualities; the epidermis to the right of the row of yellow arrows is devoid of a basal unit and, focally, shows liquefaction degeneration of the basal layer. To the left of the yellow arrows, a basal unit and a basal layer are defined. In addition, on the left, there is hyperplasia of melanocytes in the basal layer of the epidermis. Blue arrows point to a lytic cleft at the dermal-epidermal interface (xeroderma pigmentosa; LE-like lichenoid reaction).

	S13C13aP11a-4: In this area to the right, both the basal unit and the basal layer are fairly well defined. In the center of the field and to the left, melanocytes are increased in number in the basal layer. These cells have slightly enlarged nuclei; they are irregularly spaced. In some areas, they are back to back. A “clonal” interface is produced in the epidermis, on the right, in the area where the basal layer of the epidermis becomes conspicuous; the “clone” is to the left of this interface.

S13C13aP11a-5: The pattern of atypical melanocytic (lentiginous) hyperplasia (light green arrows) is interrupted in the area of the dark green arrows. The basal layer is also interrupted in this area (lichenoid reaction ). Melanophages are present in the dermis (xeroderma pigmentosa). Inflammation is not a feature; the process of lysis and death of cells appears to be intrinsic to the affected cells.

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