Ch34aP26a Molluscum Contagiosum

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F1Ch34a: This is a classic example of a lesion of molluscum contagiosum. The epithelial component is inverted; the patterns have a follicle-like quality. The mature inclusions have collected in the lumen - among keratinized debris - of what passes for the infundibular portion of a follicle. A small follicle separates the two components of the lesion. The contours of the bulbous components can be compared to those of the sebaceous gland component of a normal follicle. In this approach, the virus might be characterized as having a proclivity for sebaceous cells. As an alternative, the patterns are evidence that the virus induces sebaceous gland differentiation.


F2Ch34a: The close spacing of the epithelial components of molluscum among immature follicles, that are not visibly infected, might be offered as evidence that the initial effect of the virus infection is the induction of follicular neogenesis. In the progress of the disease, the virus preferentially seeks out developing sebaceous glands and may even promote their induction from the primitive basal cell bud. The neogenic follicles, and the virus infection have an influence on the nature of the reactive stroma; the stroma often is delicately watery or myxoid as in this field. In inflamed lesions of molluscum - late in the evolution of such lesions, after the epithelial components have been destroyed or eliminated by the process of sequestration - this stromal response offers a clue to the histopathologist as to what the original lesion may have been.


F3Ch34a: Green arrows identify a primitive hair bulb; it is situated centrally at the extremity of the epithelial process. The two bulges laterally are interpreted as sebaceous gland precursors whose development has been thwarted by the molluscum infection. Cytoplasmic inclusions first appear in squamous cells that are 3 or 4 cell layers above the basal layer; at this level, the cells of the epithelium take on the qualities of cells of the superior unit of the epidermis (i.e., cells that are committed to terminal differentiation). In contrast to the inclusions of a lesion of verruca vulgaris, the cytoplasmic inclusions of molluscum, as they enlarge, push the nucleus to one side. The discharge of the inclusions along with keratinized debris into the lumen of what appears to be an abortive follicle seems to recapitulate the release of sebum from disintegrating sebaceous cells into a lumen among keratinized debris.


F4Ch34a: The patterns have a follicle-like quality, and immature follicles are closely spaced among the follicle-like components of the molluscum infection. It would appear that the infection initially induces follicular neogenesis and, during development of the new follicle, preferentially selects the epithelial cells with a potential to develop into sebaceous glands.


F5Ch34a: This is an example of a cystic lesion of molluscum. It is not an epidermoid cyst that has been secondarily infected; it is a lesion that, in its evolution, has become cystic. The buds of basophilic cells are interpreted as evidence of abortive follicular neogenesis in the epithelial lining of the lesion.


F6Ch34a: Lobules of hyperplastic squamous cells are closely spaced. Scanty, condensed fibrous matrix separates neighboring lobules. The characteristic inclusions become evident near the interface between the basal and the superficial units.


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