Vertical Growth 1
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Common Final Pathway

Fig. 9

In this field, the characteristic changes of the “common final pathway” are manifested in the epidermis (and in the sparse representation of nests of atypical cells). For the dermal component, the representation of loosely and widely spaced nests of atypical cells, as well as the confinement of those nests to an inflamed, widened papillary dermis are requisites in the definition of the common final pathway - a distinction seen in well advanced melanocytic premalignant dysplasias. The epidermal response is lichen planus-like. In addition, the epidermis shows lentiginous and junctional, marked melanocytic dysplasia. Individual neoplastic cells and small nests of neoplastic cells have migrated into the epidermis (i.e., pagetoid spread. The cells in the junctional components show loss of cohesion. The stroma of the papillary dermis is loosely fibrous and delicate. To the left of the center of the field, a small nest of neoplastic cells is represented in the dermis (level II invasion; level II pattern. The spaces among neoplastic cells in the epidermal as well as the dermal nests can be characterized as an expanded stroma (intercellular matrix). Certainly, the nests are “large.” There are lytic defects at the dermal-epidermal interface with loss of a defined basal layer; the superficial unit of the epidermis is hyperplastic (a defensive alteration associated with a lytic process affecting the basal unit - a lichen planus-like alteration). The fibrous stroma about the junctional and dermal nests is loose and delicate; it is an activated tumor stroma. To the left at the interface between the papillary dermis and the reticular dermis, there is a band of condensed firbous tissue in which the fibers and the fibroctytes are parallel to the epidermis; a band such as this is common at the deep margin of level III lesions in association with a vertical growth component; the patterns in this field do not qualify as vertical growth.

 

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Level II Patterns

(Patterns of Regression)

Fig. 10

In this example, the pattern of nests of cells in the center of the field is insufficient in regard to the number of nests and the spacing of the nests to be characterized as early variant vertical growth. The pattern qualifies as level II “invasion” but the character of the stroma and the epidermal response is clearly different from the pattern seen in Fig. 9. The stroma is condensed and fibrotic; the nests of cells are “entrapped.” The nest near the bottom of the field is outside the zone of sclerosis and sits upon the reticuar dermis. The cells of this nest have nevus-like qualities. The epidermal changes are of a type that might be encountered in a senescent lichenoid reaction. Inflammatory infiltrates are mild, spotty and perivascular; they are not intimately associated with the nests of neoplastic cells. Cytologic atypia is moderate. Small vessels are dilated. The stromal changes are indicative of host immune response and suggest that the lesion is static and may be committed to continued regression. This change, however, often is merely a focal change in a lesion that is other areas show changes more in keeping with a progressively evolving lesion.

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Variant Vertical Growth

(one of the variant patterns as described in concept of minimal deviation melanoma)

Fig, 11a

Variant vertical growth is represented in this field. Nests of cells are loosely and regularly space in an altered papillary dermis. The number of nests with cells showing at least moderate atypia is greater than 5 and the nests are arranged in at least two strata; these gualities satisfy the criteria for a characterization of the pattern as variant vertical growth. The most significant atypia is found in the component of pigmented cells near the dermal-epidermal interface. The focus of loosely, but regularly, clustered, rounded nests on the left also qualifies as variant vertical growth but atypia is less prominent.

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Fig. 11b

In the latter area (to the left), the stroma is pink and condensed; the variant pattern here qualifies as “arrested.” In contrast, the stroma associated with the largest nests of pigmented, more atypical cells near the dermal-epidermal interface is loose and delicate. There is correspondence between degree of atypia and the stroma response. Presumably, the loose stroma is an alteration that predisposes to progresson in typical vertical growht patterns (i.e., “germination”). The more atypical nests of cells are stratified over the less atypical nests:; there is stratification as to degree of atypia and the variations are evidence of accretive growth (the process in which nests of cells are sequentially delivered from the epidermis into the dermis; a process in which it is common to find stratifications in regard to degree of atypia (with the most atypical cells found near the dermal-epidermal interface). In this approach, nidi at the dermal-epidermal interface are important in the continued delivery of nests of cells into the dermis.

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Minimal Deviation Arrested Variant Vertical Growth

(a variant pattern)

Fig. 12

In this field, the pattern is that of “arrested” variant vertical growth with a condensed, acidophilic stroma in which small nests are entrapped. The area is stratified as to size of nests (and size of cells forming the nests), and as to degree of atypia. This type of stratification is indicative of accretive growth with repeated delivery of nests of neoplastic cells into the dermis from nidi at the dermal-epidermal interface. Characteristically, such areas ofent are relatively free of inflammatory infiltrates - it is as if the condensed stroma also isolates the nests of cells from the host immune response.

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Arrested Varant Vertical Growth

Fig. 13

The quiescent nature of some examples of arrested variant vertical growth is illustrated in this field. Cellular atypia is moderately severe; chromatin is dense and nuclei vary in outline. The basic patterns - at least 5 nests forming at least two strata - satisfies the criteria for the recognition of early vertical growth. The loose, but regular, spacing of the nests identifies the type as “variant.” The character of the stroma attests to the arrested character of the process.

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Arrested Variant Vertical Growth

Fig. 14

In this area of a neoplasm, the pattern is that of arrested variant vertical growth - with reference to the criteria in the above legend (see Fig. 13). The nests are rounded and small; the degree of atypia is moderate to moderately severe; and the stroma is condensed around each nest. In this example, the stroma is composed of loosely arranged, coarse, hyalinized fibers; the fibers take the character of altered basement membrane material. Perhaps, this alteration might be cited as offering support for the notion that the stroma functions as an immunologic barrier.

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