S9C13P6Morphea

S9C13P6-1: In the lower 1/3 of the field, the interstitial infiltrates of a lymphohistiocytic collagenosis are associated with coarsening of collagen bundles. Some of the bundles are fissured longitudially. Perhaps, this type of fissuring provides an explanation for the patterns of “streaked” collagen bundles that are so characteristic of late lesions of morphea.A longitudinal fissuring of a collagen bundle, followed by accretive or substitutive fibrosis along the fissures, might eventuate in the appearance of several collagen bundles, all arranged in a parallel array (and that array usually oriented parallel to the surface of the skin). In the upper portion of the field, the fissuring of collagen bundles is again a feature but, in addition, the interstitial spaces are widened; this alteration apparently is the rare expression of a focal mucinosis in the setting of morphea (the two processes are not mutually exclusive).

S9C13P6-2: Collagen bundles, in this area of interstitial fibrosis in a lesion of morphea, are coarsened, but are also fissured and fibrillated. Delicate collagen fibers are identifiable in the pale pink zones among collagen bundles (red arrows). The delicate fibers might be interpreted as either a manifestation of fibrillation at the periphery of a bundle, or as a new deposit along the surface of a pre-existing bundle (accretive fibrosis). Alternately, the patterns may be evidence of deposition of new fibrils among old fibers that have been spread apart during fibrillation and clefting (interstitial fibrosis).

S9C13P6-3: In this area, the lymphohistiocytic collagenosis of morphea has features which might be cited as being in favor of a component of mucinosis; the collagen bundles are widely spaced and the spaces probably are evidence of an increase in the amount of interstitial mucinous matrix.

S9C13P6-4: At a higher magnification, the interstitial spaces are faintly mucinous; this probably represents an exaggeration of a mucinosis which commonly affects dermal connective tissue during the evolution of a lesion of morphea, but usually is inconspicuous. It is a preparatory change in anticipation of a new deposition of collagen fibrils in the dermis.

S9C13P6-5: This elastic stain accentuates the patterns of “streaked” collagen bundles that characterize the deep portion of the dermis in a mature lesion of morphea. The process is not significantly elastolytic; rigid, black elastic fibers are among, and parallel to, the altered collagen bundles. The sclerosis extends a short distance along a fibrous septum into the adipose tissue. Looking at this field, it might be difficult to envision a process of fissuring of collagen bundles, as an explanation for the prominence of coarse collagen bundles in parallel arrays.

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