S3C14P3-LS

S3C14P3-ls (to the right)

LICHEN STRIATUS

S3C14P3-1 (left) (lichen striatus): the epidermis shows acanthosis and elongation of rete ridges. Lymphoid infiltrates are mild, they are perivascular in the dermal papillae. Focally, they migrate into the epidermis at the tips of the rete ridges. There is liquefaction degeneration at the dermal-epidermal interface.

This is a primary lichenoid reaction in which the epidermis shows prominent psoriasiform qualities (patterns are both lichenoid and psoriasiform). The spotty, mild infiltrates of lymphoid cells are a common feature of this variant of a lichenoid reaction. This might be characterized as an immuno-stimulatory (young or primary) phase of a lichenoid reaction.

S3C14P3-2a (left above) (lichen striatus): The pattern in this lesion differs from that of P3-1 by showing inter-cellular edema of the epidermis and by the presence of spongiotic vesicles in the keratin layer. The basic epidermal patterns and the distribution of the infiltrates are both psoriasiform and lichenoid. In P3-2b, in a region showing lichenoid phenomena, there is an increased prominence of mucinous matrix among keratinocytes at the tip of the dermal papilla. The spaces among the keratinocytes are irregularly widened; the defects are an expression of the effects of the mild lichenoid reaction.

This example is spongiotic, psoriasiform, and lichenoid. In a sense, this combination might be characterized as pityriasic. In a primary lichenoid reaction, the distinctions between spongiosis and an early lichenoid reaction are difficult to define.

S3C14P3-3 (left) (lichen striatus): The patterns are basically similar to those of P3-2a, but the infiltrates are more prominent. There are band- like infiltrates in the papillary dermis. The infiltrates are diffuse among keratinocytes of the hyperplastic basal functional unit. The green arrows help to define the boundaries of the rete ridges in the diffuse infiltrates. This example shows a florid infiltrate of lymphoid cells in the widened papillary dermis; the infiltrate extends into the basal unit of the epidermis. The pattern is that of a primary lichenoid reaction.

In this primary lichenoid reaction, the interface between the basal unit and superficial unit also defines the limits of the upward migration of the lymphoid cells. The lymphoid cells are mostly denied access to the superficial unit. A primary lichenoid reaction would, for most examples, be the equivalent of a pityriasic reaction.

S3C14P3-4 (right) (lichen striatus): The pattern in the epidermis has acquired the features of an established lichenoid reaction; it has lichen planus-like features. Lytic defects at the dermal-epidermal interface are identified with blue arrows. The rete ridges are eroded; some have pointed extremities.

S3C14P3-5 (left) (lichen striatus): To the left in this field, infiltrates in continuity with the dermis have produced a focal lytic defect in the epidermis; the defect is separated from the surface by only a single layer of cells (a vestige of the superficial unit has maintained the integrity of the epidermis at this level). To the right, rete patterns are effaced and the basal layer is reconstituted; the infiltrates are mild; the pattern to the right is that of a senescent phase of a lichenoid reaction.


	S3C14P3-6 (right) (lichen striatus): To the left of the center of the field, the pattern is psoriasiform; to the right, the pattern is that of a senescent lichenoid reaction. The broken green line defines the boundary between the superficial unit and the basal unit; the blue line extends between the tips of the longer rete ridges and the dermis. Lytic defects are present at some of the tips.

S3C14P3-6: A portion of the epidermal domain to the right of the center of the field has been lost to the dermis. Clearly, it is the basal unit that has contributed its domain. The defect has been inlaid with newly formed, inflamed fibrous tissue. To the left, lichenoid patterns of an established type are represented at the tips of rete ridges. Primary, established and senescent features are all represented.

S3C14P3-6 (con’t): Two stages of the cell-rich lichenoid reaction are represented. Lytic defects are present at the tips of rete ridges on the left. On the right, fibrous tissue has been inlaid in the defects at the dermal-epidermal interface (accretive fibrosis). The space between the blue and green lines is a rough gauge of the amount of epidermal domain lost to the dermis in the evolution of the lichenoid reaction. The thin epidermis in this same area is a measure of the thickness of the surviving superficial unit of the epidermis; the basal unit has suffered the major damage.

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