HYPERTROPHIC LICHEN PLANUS
The hypertrophic variant of lichen planus (HLP) is seen most frequently on the legs. This usually presents as a plaque though there may be small polygonal papules in the immediate vicinity. This may or may not be associated with lesions of lichen planus elsewhere. The lymphocytic infiltrates are often less dense than in classical lichen planus, and much of the 'hypertrophy' is actually secondary to repeated rubbing or scratching (secondary lichenification). Therefore, HLP can be mistaken for lichen simplex chronicus (LSC). Enlarged keratinocytes in all layers of the epidermis plus occasional colloid (Civatte) bodies may be the only clues that this is HLP rather than LSC. Hypertrophic discoid lupus erythematosus (HDLE) enters the differential diagnosis, but basement thickening in characteristically found in HDLE.

From the leg of an adult:
 
Scan power view. Note the extreme degree of acanthosis. 
Medium power view of above. Note the vertical streaking of collagen which is a feature of severe secondary lichenification. Marked acanthosis can be produced by repeated rubbing or scratching.
High power of above. Civatte (colloid) bodies are present. Note the universal keratinocyte enlargement which can be seen in LP and in LE (plus a few other things). There is no basement membrane thickening in LP.

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