S9C19P11LSA

S9C19P11-1: The pattern at the dermal-epidermal interface is both cell-poor and lichenoid; there are lytic defects at the dermal-epidermal interface. A defect to the right of the center of the field contains lymphocytes and histiocytes. Green arrows identify migratory histiocytes. Red arrows identify colloid bodies (necrotic keratinocytes) (LS&A).

In the search for a proper subtype of lichenoid reaction, the features would support a characterization of the reaction as lichen planus-like, but clearly the process is not classic lichen planus. Hyperkeratosis, hyperplasia of the superficial epidermal unit with exaggerated features of terminal differentiation, and an absence of a basal unit are lichen planus-like features. In addition, there are lytic defects in the epidermis at the dermal-epidermal interface. There is a partial fibrous inlay in a zone in which the lichenoid reaction has eroded a rete ridge (at the extremity of the defect); the inlay is at the lower extremity of the defect. In this same inlay (just to the right of the center of the field), basement membrane is reduplicated.

S9C19P11-2: Membranous hyaline deposits are distributed in apposition to the epidermis at the dermal-epidermal interface. The adjacent papillary dermis is loosely fibrous with lymphoid cells and histiocytes among the collagen fibers. A lytic defect (just above the center of the field) at the dermal-epidermal interface contains a few lymphoid cells and melanophages. It is outlined on the dermal side by the hyaline membrane ( LS&A). In other areas, the hyalin was not so confined at the dermal-epidermal interface; the patterns were more characteristic for LS&A. In this field, the early pattern of hyalinization might be taken as evidence that the material is specialized fibrous tissue of basement membrane-like type.

S9C19P11-3: The patterns of radiodermatitis share features with both LS&A and with LE. In this example of radiodermatitis, the patterns are lichenoid at the dermal-epidermal interface. The interface is straight and there are vacuolar changes. In contrast to most examples of LS&A, the basement membrane is thickened and hyalinized. The dermis, adjacent to the basal layer of the epidermis (i.e., deep to the basement membrane), is fibrotic. In the lower portion of this field, the fibrotic dermis shows elastosis. Characteristically, skin appendages in an area of radiodermatitis are atrophic (as in this lesion). Areas of fibrinoid degeneration are also a common feature. Focally, the basal unit of the epidermis is represented and shows some degree of atypia (a common finding).

S9C19P11-4: In this second example of radiodermatitis, skin appendages are atrophic and vessels are ectatic. The epidermis shows hyperkeratosis. Areas of acanthosis alternate with areas of atrophy. The dermal-epidermal interface is straight. The superficial unit of the epidermis is hypertrophied. Individual keratinocytes are enlarged; they show increased cytoplasmic acidophilia (a quality of keratinizing cells and a histologic correlate of the process of terminal differentiation). The pale, fascicular structures scattered throughout the reticular dermis are fascicles of smooth muscle cells (arrector muscles). Near the epidermis, the dermis is hyalinized and edematous; beneath this zone, the dermis is fibrotic.

S9C19P11-5: This area of LS&A shows atrophy and hyalinization of dermal connective tissue. In addition, there is marked edema, particularly in the right upper corner. Yellow arrows point to elastotic material, a marker documenting involvement of the reticular dermis by the distinctive, sclerosing process .

S9C19P11-6: The hyaline matrix in this area of LS&A somewhat resembles the matrix of hyaline cartilage. Vessels are ectatic. There are areas of edema. Yellow arrows point to an area showing fibrinoid degeneration; the fibrin is deposited in fissures in the dermal matrix.

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