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1. Histopathology of Inflammation

2. Minimal Deviation Melanoma, etc.

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F1Ch30: This is another photograph of the patterns seen in an irritated seborrheic keratosis (Ch29). The epidermis is thin with representation of a basal, and a superficial unit. Thin cords of squamous cells project from the epidermis into the dermis; within the cords, some of the cells form compact whorls. The supporting stroma has been infiltrated by a pale, homogeneous matrix (epithelial amyloidosis). Some of the material is globular in outline; there are scattered angulated fissures. Deposits of amyloid are fairly common in seborrheic keratoses, especially the irritated variants. For this example, they are unusually prominent.

F2Ch30: This is another low-magnification photomicrograph of the lesion illustrated in Ch29. Some of the surface irregularities represent distention of the false follicular orifices of seborrheic keratoses (the keratin-filled cysts); these cysts have the characteristics of dilated infundibular orifices.

F3Ch30 (G5188): In this photograph of a faded section, many of the features of an “irritated seborrheic keratosis” are represented. Columns of squamous epithelium project from the epidermis into a widened papillary dermis. They are irregular in outline and, focally, the neighbors are confluent. Many of the squamous eddies are accentuated by their central collections of keratinized debris. There are focal areas of lysis, particularly at the extremity of the keratin-filled, inflamed ostium to the right of the center of the field. The distinctive columnar patterns set the lesion apart from “irritated seborrheic keratosis.”

F4Ch30(G5188): Areas of cytolysis are evident among degenerating squamous cells at the extremity of the keratin-filled ostium. To the left, whorls of squamous cells are a prominent feature.

F5Ch30 (G5188): In this field, squamous eddies are a prominent feature. Many of the eddies show central collections of acidophilic, keratinized debris. The compact debris is not a characteristic of infundibular or sebaceous differentiation. If the patterns of the inconstant portion of a regressing follicle are selected as a reference model, there are similarities.

Focally, dendritic cells, compatible with melanocytes, are sprinkled among keratinocytes (in the background population, rather than among the cells forming the whorls). A few small clefts have formed at the interface between some of the whorls and the background population. The background population seems to bear the brunt of the cell damage in areas in which lysis and degeneration of cells become prominent features.

F6Ch30: Basal unit and superficial unit patterns are represented; in areas, the cells of basal   unit-like type are widely spaced. Lymphoid infiltrates have extended into the basal unit-like components in some of these areas. Whorls, that are composed of cells of the superficial     unit-like type, are a prominent feature. Patterns of differentiation which resemble those of the outer root sheath are not a feature of any of the pictorials of this portion of this chapter.

Not all “inverted follicular keratoses” are limited in distribution to the butterfly area of the face. Some of the lesions that involve sites other than the face tend to be large; they measure greater than 1 cm. in diameter; they may push into the subcutaneous tissue. The lesion of chapter 45 is an example. Similarly, there are rare giant tricholemmomas of classic type; they tend to be solitary lesions, and may be encountered on sites other than the butterfly area of the face. Some of the tumors, that arise in nevus sebaceus, qualify as variants of tricholemmoma. This is a feature of some interest; the abortive follicles of immature variants of nevus sebaceus tend not to be associated with an outer root sheath. This attribute may merely reflect the immature nature of the follicles in many examples of nevus sebaceus.