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For melanomas of the common type, if the biopsy has been conservative with only a few millemeters of uninvolved skin or, if the margins are involved by the vertical or radial growth components, a currently popular guideline is a recommendation for a re-excision with a margin of 1 cm for each 1 mm of height in the vertical growth component. To endorse an even more conservative approach may lead to a charge of malpractive, if the subsequent clinical course is complicated by local recurrence, satellitosis, or nodal metastases. There is some evidence that margins less than 1 cm may be associated with an increased incidence of local recurrence. The 5 cm margins which have commonly been utilized in the past are currently touted as unnecessary even for “thick” lesions. In this area of controversy, respect for the nature of a melanoma may take precedence over the recommendations for treatment, if the recommendations are based solely on statistical analyses. Common sense may be an important attribute in providing recommendations regarding the need for wider margins of excision.
A pathologist who finds himself a defendant in a malpractice suit in which the adequacy of margins of excision is a contention may be chagrined to find that a proponent of the more conservative approaches to margins of excisions has found fault with the defendant’s performance, and has agreed to serve as an expert for the plaintiff (the needs of an “expert’s” ego commonly outweigh his needs to support his recorded recommendations).
Intravascular nests of tumor cells in the immediate vicinity of a vertical growth component are a flag identifying a risk for both local recurrence, and metastasis.
Local recurrence may be in the form of a true local recurrence in which a portion of the original lesion was left behind at the time of the original biopsy. Most “local recurrences” represent local metastases (within 2 cms of the original site of the biopsy), and many are actually immediately adjacent to, or beneath, the original biopsy site. Recurrent melanoma often is situated in the lower dermis and subcutis. It tends to be expansile, and may even be outlined by a condensation of inflamed fibrous tissue. Many examples are relatively devoid of inflammatory infiltrates. A local recurrence in the excision site (i.e., within 2 cms of the excision site) of a primary melanoma evokes a variety of virtual images. If the first indication of a mistaken diagnosis following excision of a problematic lesion is a local recurrence within the region of the scar, the histologic character of the local recurrence must be defined. If on review of the initial histologic sections a vertical growth component of a primary melanoma had been cut across at a surgical margin, and if the subsequent recurrence is superficial, is manifested in patterns of verticl growth, and is in continuity with the epidermis ( and likely to be associated with remnants of a melanocytic dysplasia or radial growth component in the overlying or adjacent epidermis), the recurrence would be properly characterized as a post-surgical persistence of a primary melanoma.
If, in a somewhat different scenario, the histologic sections of a primary melanoma, on review, show only radial growth at the surgical margin, then the nature of the radial growth component must be defined. Much of what currently is accepted as radial growth is best interpreted as a persistence of the population of dysplastic cells from which the vertical growth component ensued (3). If only radial growth had been cut across by an initial incomplete excision, and the lesion subsequently recurred both superficially in the dermis (in vertical growth patterns), and at the dermal-epidermal interface (in “radial growth” patterns), then conceptually the vertical growth component in the “recurrent” lesion may in fact represent a new primary melanoma (i.e., a lesion in vertical growth), one that has ensued from the remnant of the same radial growth component from which the original vertical growth component had its origin. In this scenario, the same phenomena which gave origin to the first melanoma (herein, melanoma is defined as a lesion in vertical growth), would have been recapitulated in the remnant of the radial growth component. If the recurrence is “primary” in configuration, and within the confines of the scar of the original surgical procedure, the possibility that the “recurrence” is a local, epidermotropic metastasis (satellite) must also be considered (10).
In a somewhat different scenario, surgical margins of excision of the primary lesion will have been found to be histologically free of involvement, and a “recurrence” which lacks a primary configuration will have been found to involve the deep dermis and subcutis. For a lesion with these features, the most likely explanation for the recurrence is that it represents a metastasis to the deep dermis and subcutis. In this scenario, the primary lesion may be identified as not only having had the capacity for metastasis prior to the initial biopsy or excision, but also as having locally metastasized prior to the original excision. In such a setting, the “adequacy” of the margins of excision of the initial biopsy specimen likely will be questioned. In assessing the culpability of a pathologist, who may have imposed false, “benign” virtual images in his initial interpretation of what later proved to be a primary melanoma, the demonstration of a capacity for metastasis (as manifested in a deep, local recurrence) must be afforded great significance. In this scenario, any harm is properly attributed to an act of nature, as an expression of nature’s way: the decisions and interpretations of the original pathologist are merely incidental. In practice, metastases to regional lymph nodes commonly appear shortly after, or even synchronously with, the appearance of a metastatic, subcutaneous nodule in the site of the primary excision. In addition, distant metastases often follow, in short order, the appearance of the nodal metastases. Such events, occurring at close intervals, provide support for the interpretation that all of the metastases are more or less synchronous, and that they occurred prior to the initial excision of a primary lesion (based on the premise that the original margins of excision were found to be histologically free of involvement). A “recurrence” in this scenario would represent growth of tumor in what was an occult (micro-) metastasis at the time of the original excision. The current emphasis on conservative local excisions would seem to make the “error” incidental to the observed phenomena (post hoc, ergo propter hoc).
Metastases:
Metastases are generally characterized as discontinuous spread of tumor, but this characterization gives recognition to neither the fluid phase of malignancies (e.g., migrant or diffuse level IV invasion of melanomas), nor the connectiveness of various organ systems by way of the vascular system.
Distinctions should be made between local recurrences, and local metastases. If the margins of an excisional biopsy of a melanoma (i.e., a lesion in vertical growth) are histologically free, then the subsequent appearance of tumor in the lower portion of the dermis and the subcutis qualifies as a local metastasis. If, on the other hand, the margins of the excised specimen were histologically involved by tumor, and the biopsy site had not been re-excised with clear margins, then a distinction between local recurrences, and metastases cannot be established with certainty, but the burden would be on those who would promote the problematic lesion as a metastasis.
Lymphatic metastases are derivatives of a lymphatic component of the fluid phase of vertical growth. Hematogenous metastases are derivatives of a blood vascular component of the fluid phase of vertical growth. The two are independent (i.e., tumor does not selectively go first to regional lymph nodes, and then disseminate to the viscera by way of the blood stream). The two events may be synchronous or isolated.
The designation, “in transit metastasis,” is used in an inconsistent manner to characterize cutaneous metastases in the pattern of satellite lesions between a primary site, and the respective regional lymph nodes. Originally, the concept was promoted as a justification for allowing an interval of time between excision of a primary lesion, and a dissection of regional lymph nodes. The rationale was that the delay would give tumor cells, which might be free in the lymphatics, an opportunity to complete their journey from the primary site to the regional lymph nodes, the supposition being that not all lymphatics are open and functioning at all times; tumor cells could be sequestered within vessels that would not be functionally “open.” A short interval would provide the opportunity for the sequestered cells to find their way into a functioning tributary, and to then be delivered to the regional nodes. If, along this line, the primary excision, and the node dissection were to be performed concurrently, the “in transit” component would be more likely to become sequestered in the altered flow of lymph, to locally implant, and to then produce local satellites.
The designation, satellitosis, gives recognition to cutaneous metastases in the vicinity of the site of a primary melanoma; an individual example is a “satellite” lesion. The metastases are visible on the surface of the skin; they are superficial. Often, satellites are not associated with prominent lymphoid infiltrates.
In “satellitosis,” regional cutaneous metastases may be evident at the time of excision of the primary lesion. They may appear following excision of histologically positive regional lymph nodes. In all examples of regional cutaneous metastases, which first become clinically apparent after a regional lymph node dissection, the most likely explanation is that the tumor cells were already implanted in the lymphatic vessel at the time of the excision of the primary melanoma, but the implants were indolent in growth, and late in producing clinical manifestations. This is the most likely sequence regardless of the presence, or absence of a recurrent nodule of tumor in the excision site of the primary melanoma. If a distant, solitary cutaneous metastasis is followed by the appearance of multiple lesions in its immediate vicinity, then these might also be characterized as satellites.
A demonstration of a dermal and epidermal component (the latter in lentiginous, or lentiginous and junctional patterns) is required to qualify a satellite as epidermotropic. Such a lesion is distinguished from a new primary by the confinement of the lentiginous and junctional component to the epidermis over the dermal component (no significant radial spread), and by a high grade, monomorphic population of cells in the dermis. Generally, such a lesion is small, but often shows level IV invasion. Some of these small, high grade lesions may also show neurotropic spread along small nerves in the underlying dermis. Lymphoid infiltrates often are inconspicuous.
In some patients, many epidermotropic satellites are purely lentiginous and junctional; they have the qualities of primary configuration. Some examples of so-called epidermotropic metastases may be primary lesions, and may represent a field effect in which neoplasia is multifocal, and widespread in a regional distribution and, in addition, is high grade.
Metastases and thin MDM:
In the size ranges of 1 mm or less, rare thin, small, compact melanomas metastasize (9); in the act, they will have demonstrated their nature as borderline, or incipient melanomas, regardless of how the real and virtual images, and the assigned linguistic forms may have been manipulated prior to the appearance of the metastases. Often, such offenders also manifest thin, level IV invasion, and may be relatively free of lymphoid infiltrates; often they also are fascicular (spindle cell) variants.
Areas of regression are common in thin metastasizing melanomas. A note of caution (conservative prognostic evaluation) is required in the prognostic evaluation of thin “melanomas” showing focal areas of regression. To identify a relationship between regression and metastasis is not the same as an identification of all thin “melanomas” with areas of regression as lesions that have metastasized. In such lesions, the areas of regression are simply an indication that real images, and biologic behavior are not always congruous.
Micrometastases:
Microscopic foci of melanoma, that are not in continuity with the epidermis, are sometimes present in the dermis in the immediate vicinity of, but are not part of, the primary lesion. They may be represented as small irregular nests of compactly aggregated cells, or as traceries of cells among collagen bundles of the reticular dermis. It is sometimes possible to identify tumor emboli in small dilated vessels beneath the vertical growth component in such lesions.
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