S12C14aaP4aa-1: In the dermis, to the right of the center of the field, histiocytes form traceries among connective fibers. A zone of uninvolved dermis on the right is peripheral to the interstitial infiltrates. In this area, the dermis shows solar elastosis. The interstitial infiltrates are most cellular at the interface with the univolved portion on the far right; to the opposite side (the left), the infiltrates trail in regard to degree of cellularity. The zone of greatest cellularity is the advancing margin of a lesion that is spreading centrifugally, from left to right. Left behind in the dermis, as the lesion advances to the right, is a trail of altered fibrous tissue; the trail is relatively devoid of elastic material, particularly the altered product which characterizes solar elastosis (actinic granuloma).

S12C14aaP4aa-2: At the opposite side from that seen in S12C14aaP4aa-1, the patterns are similar. The zone of greatest cellularity is the advancing margin of a histiocyte-mediated process of granulomatous elastolysis. Here, the trail extends to the right. The technique has been altered to accentuate the pale, basophilic, elastotic material in the uninvolved dermis to the left of the advancing margin of the lesion.

S12C14aaP4aa-3: In this field, the advancing margin is to the right, and the trail is to the left. The trail is a zone of loosely cellular, fibrous tissue showing thin, fibrous lamellae. The lamellae are parallel to the surface; the trail has the qualities of a scar. Coarse, acidophilic collagen bundles of the pre-existing reticular dermis are partially preserved among the clusters of histiocytes (red arrows to the right) at the advancing margin.

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