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MDMHALO

MDMLMM

NEVOIDMDM

MDMhalo, metastasizing

Near-neoplasia

General Index

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PICTORIAL 1

PICTORIAL 2

PICTORIAL 3

PICTORIAL 4

P1a-1: halo nevus with prominent junctional component in which cells are spindle shaped and pigmented. There is moderate atypia in the junctional component with variations in nuclear size and staining and also loss of nuclear polarity. Some of the melanocytic cells, individually and in small nests, have infiltrated the epidermis (proponents of “melanoma in situ” might be hard put to characterize this lesion). Green arrows identify two dermal nests (fascicles) of “nevus cells.” The cells are small in these two nests but show slight increase in amount of cytoplasm and variations in nuclear size and staining; nuclear chromatin is dense. These nuclear qualities are common in the dermal component of halo nevus but have rarely been commented on in the literature. An additional dermal nest is identified by a blue arrow. In it, the atypia is more pronounced (moderate). Variability in nuclear size, staining, outlines, and orientation is greater in this nest than in the two nests identified by the green arrows. This degree of atypia is also acceptable in the setting of “halo nevus” but could also be cited as the basis for classification of this “halo nevus” as a new growth and for characterizing the cytologic features, particularly in the nest near the blue arrow, as early epithelioid cell transformation (incipient near-neoplasia). For this lesion, it would not be inappropriate to characterize the respective lesion as early or young, near-neoplasia of halo nevus-like type.

P1a-2: At higher magnification, the cells of the junctional nests clearly are pigmented and have spindle cell and dendritic cell qualities (red arrow). Nuclei have central nucleoli. These features are not clearly Spitz nevus-like but on the other hand, a great deal of latitude is afforded by proponents of a wide histologic spectrum in the parcel of virtual images for the interpretation of “Spitz nevus.” Near the blue arrow, cells of the identified nest are more polygonal and have pale amphophilic cytoplasm. The cells show variability in nuclear size, staining, outlines, and orientation. Some of the nuclei have prominent nucleoli. This degree of nuclear atypia in a dermal component is acceptable in the current definition of “halo nevus” but perhaps this type of atypia indicates a need to reexamine the nature of “halo nevus.” RETURN to Discussion A, NOTE 1.

Note 2: Cytolysis is inherent in the concept of halo nevus-like phenomena. Lysis of melanocytic cells and resolution of lymphoid infitrates often leave behind a delicate, vascularized fibrous matrix (see below).

P1a-3: This is one margin of the same lesion as seen in P1a-1 & 2. This is a characteristic senescent change of halo nevi and related variants; although, in some example the late changes have a sclerosing quality. A junctional nest is represented to the right of the field. RETURN TO Discussion A, note 2.

Note 3: Lichen planus is a cell-mediated, cytolytic process. In it, the effects of the cytolytic process are manifested by lytic defects in the epidermal domain of the basal epidermal unit. The defects are not reclaimed by regeneration of keratinocytes; instead, the defects are inlaid by newly formed fibrous tissue in accretive patterns; sclerosis is often a significant part  of the evolution and resolution of cell-mediated immune reactions that are invasive and destructive in nature (see below).

P1a-4: The modifications in the mucinous avenues of the epidermis during the evolution of a lichen planus-like reaction are illustrated. Following a stage of cytolysis in the epidermal domain, new fibrous tissue forms as an inlay in the lytic defect; the inlay of fibrous tissue marks the senescent phase of a lichen planus-like reaction. The lichen planus-like reaction is classic example of cytolysis as manifested in a cell-mediated immune reaction. Such a reaction is encountered in a variety of organ system as an expression of cell-mediated immunity. In the dermis, some of the mucinoses probably are an expression of comparable phenomena. The halo nevus-like reaction might be cited as an additional example in which the target is a minimally deviant, neoplastic melanocyte.

P1a-5 & 6: On the right (fig. P1a-6), a similar defect in an epidermal domain is represented but organization is more advanced. In addition, numerous colloid bodies (a marker for what was at one time epidermal domain) are entrapped in the newly formed fibrous tissue. This sequence is characteristic of a lichen planus-like reaction in the senescent phase but the basic changes can be transposed to other domains with other target cells. In certain forms of new growth in the melanocytic system, we speak of this cell-mediated process as halo nevus and can identify lytic as well as senescent phases.  RETURN to Discussion A, note 3)