S1C14P4Perforations


S1C14P4-1: The concept of the perforating disorders should be restructured to give recognition to: 1.) the active role of invasive epithelium, and 2.) the passive role of the connective tissue fibers (for those examples in which connective tissue fibers are the “perforating” components). In this example, collagen bundles perforate the epidermis (elastic fibers are also represented in the epithelial interstitium, but are less conspicuous). As in the “perforating” elastoses, it is the epithelium that is the prime mover. In this example, hyperplastic epithelium has grown into the reticular dermis; it has disrupted connective tissue fibers. The broken fibers have been entrapped; they are in the process of being extruded at the surface. In contact with the epithelium, the connective tissue fibers are cytotaxic for neutrophils (blue arrows point to a neutrophilic response to a collagen bundle in the keratin layer). Green arrows point to collagen bundles in transit through the epidermis to the surface ( perforating collagenosis).


S1C14P4-2: (photomicrograph taken in the 1960’s using B&L optical bench, bellows and B&L microscope with apochromatic lenses) Lesion of perforating collagenosis showing collagen bundles in transit through the epidermis to the surface (green arrows). Some of the epidermal defects on the left appear to be empty, but this is interpeted as a technical artifact. The keratinocytes of the epidermis are pale; the cytologic features might be compared with those in a lesion of keratoacanthoma.

S1C14P4-3: With a Masson trichrome stain, the blue collagen bundles can be traced from the dermis into the epidermis, and then into the collected cellular debris beneath the keratin layer. Perforating collagenosis is probably a variation of patterns seen in the setting of neurotic excoriations.

S1C14P4-4: Elastosis perforans serpiginosum basically is an elastosis in which the presence of abnormal elastica in the vicinity of the dermal-epidermal interface evokes an invasive epidermal hyperplasia. In addition, the close association between elastica of reticular dermal type and epithelium induces an inflammatory response. The epithelium encloses the abnormal elastica. The entrapped elastica is transported to, and discharged along, the surface of the skin. The process spreads centrifugally; it leaves behind a trail of abnormal fibrous tissue. This trail is devoid of the abnormal elastica. Green arrows identify the advancing margin of the process. The column of epithelium is directed toward this zone (to the left). The elastica-free zone to the right of the arrows is the trail.

S1C14P4-5: In this area, elastic fibers (green arrows) are within the lumen of a defect that is lined by hyperplastic epithelium; the epithelium is of follicular origin. This is a “perforating folliculitis,” but the prime mover in this process is the column of hyperplastic squamous epithelium. The defect in the column may represent a defect produced by a jet of follicular contents into the dermis in response to external pressure (i.e., squeezing).

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