Quiz 7: What is your diagnosis?

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Diagnosis: Quiz 7

Quiz 7

Answer: Metastasis of melanoma

Criteria for diagnosis histopathologically:  An asymmetrical neoplasm characterized by a decidedly uneven base and composed of aggregations of melanocytes situated immediately beneath the epidermis, as well as melanocytes organized in nodules and in cords and strands, the latter between thickened bundles of collagen in the upper part of the reticular dermis but also as solitary units in a lymphatic dilated widely, is a metastasis of melanoma.

Differential diagnosis histopathologically: This is not a primary cutaneous melanoma, despite the fact that some aggregations of melanocytes seem to be positioned at the dermoepidermal junction, there being no increase in number of abnormal melanocytes disposed as solitary units at that junction.

Criteria for diagnosis clinically: Numerous black papules variable in size and shape, some of them agminated, scattered randomly, are those of metastases of melanoma.

Differential diagnosis clinically: There is none.

Clinicopathologic correlation: The papule is formed of neoplastic melanocytes in the upper part of the dermis, it is black because the neoplastic cells are suffused with melanin, and the surface of it the lesion is smooth because the stratum corneum is normal.

Options for therapy predicated on knowledge of histopathologic findings: Because this is a metastasis, no adjuvant therapy available currently, no matter how highly touted, can be depended on as being effective.

1) A metastasis of melanoma to skin may be associated with aggregations not only in contiguity with the epidermis, but within the epidermis itself. That phenomenon, known as epidermotropically metastatic melanoma, sometimes is difficult to distinguish by microscopy conventional from primary cutaneous melanoma. Differentiation is accomplished by noting absence of an increased number of abnormal melanocytes disposed as solitary units at the dermoepidermal junction, a finding indicative of a primary melanoma and missing from a metastasis, such as the one shown in these photomicrographs.

2) The presence of neoplastic melanocytes in a lymphatic dilated markedly in the upper part of the reticular dermis represents, for purposes practical, metastasis of melanoma, but in itself does not convey whether the metastasis is from a primary melanoma in the skin or of a metastasis of melanoma from another site to  the skin. It is unusual in the extreme for a primary melanoma as relatively "thin" as the metastasis of melanoma pictured here to be associated with "intravascular invasion" by neoplastic cells. Parenthetically, the well-circumscribed, smooth-bordered nodule of neoplastic melanocytes very nearby the obvious endothelium-lined space containing abnormal melanocytes could be housed within the very same lymphatic.

3) Although the changes in these photomicrographs must be differentiated from those of a primary melanoma, that is not the case for the lesions clinical; the diagnosis, at a glance, is metastasis of melanoma.

4) When neoplastic cells of melanoma, especially ones metastatic to skin, are interposed between bundles of collagen in the reticular dermis, those bundles often are thickened. Alterations in collagen similar to the ones illustrated here are encountered sometimes in a metastasis of other kinds to skin, such as from carcinoma of the breast, but also in primary cutaneous neoplasms as disparate as "common" blue nevus on one hand and "keloidal" basal-cell carcinoma on the other, the denominator all of them share being interposition of neoplastic cells between bundles of collagen in the reticular dermis.

5) Another clue to the particular neoplasm presented here being a metastasis of melanoma rather than a primary one is that at the periphery the dermis is affected strikingly in the absence of any sign above it of melanoma in situ. By contrast, in primary cutaneous melanoma, a component in situ usually extends for some distance beyond the component in dermis.

6) The numerous individual dull pink globules present in the upper part of the dermis on the right side of the melanoma are necrotic cells, either keratocytes or neoplastic melanocytes. It is impossible to state with assurance which of those two types of cells they are on the basis of attributes histopathologic or cytopathologic alone. That the necrotic cells are arranged in a cluster in an infundibulum and as solitary units in an eccrine duct very nearby is no help in coming to a determination about the nature of them, i.e., keratocytic or melanocytic. The fact that the pink globules have not the slightest tinge of brown conveyed by melanin militates somewhat against their being necrotic melanocytes. All that having been said, no firm decision can be made about the essential character of the pink globules.

7) It is fashionable, circa 2006, to designate the pink globules in the upper part of the dermis and in structures epithelial (an infundibulum and an eccrine duct) "apoptotic cells." For the better part of a century, those cells were called "hyaline bodies," "colloid bodies," and "Civatte bodies," the judgment of histopathologists insightful in the last quarter of the 20th century being that they represented necrotic cells. On grounds morphologic alone, as visualizable in sections stained by hematoxylin and eosin, it cannot be argued compellingly that those dead cells should be termed "apoptotic" and not "necrotic"; the criteria histopathologic are the same!

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