malignant melanoma, superficial spreading type, symmetrical

MALIGNANT MELANOMA, SUPERFICIAL SPREADING TYPE (CLARK'S CLASSIFICATION) THAT IS SYMMETRICAL

Other than being relatively symmetrical, this lesion has the classical features of a malignant melanoma that would be classified by the radial growth component as superficial spreading type by Clark's criteria. The term superficial spreading is unfortunate in that this designation could be misinterpreted to mean that invasion is necessarily superficial. Superficial spreading, as used by Clark, implies a concept of the developmental biology of the lesion, specifically the pattern of development of the intraepidermal component. This has nothing to do with the level of dermal invasion. Clusters of melanocytes that have epithelioid cytologic characteristics are found in the lower epidermis and these are associated with similar single cells (pagetoid melanocytes) that have migrated into the upper levels of the epidermis.

The invasive component in a superficial spreading melanoma often evolves into expansile clusters of cells having epithelioid characteristics, and these cells have apposing cytoplasmic borders. This is the pattern that is seen in typical vertical growth as discussed by Reed.

Although melanomas most often have asymmetrical profiles, occasional examples are encountered that are relatively symmetrical. This has no known influence on prognosis.

From a 27 year old female:

Very low power view (direct scan of glass slide). This profile of this melanoma is relatively symmetrical.

A high power view of the epidermis. Pagetoid melanocytes (PM) are in the stratum granulosum. Atypical junctional melanocytes are found in a cluster that has been cut off in the right side of the picture.

A medium power view of the lower epidermis as well as papillary dermis. Clusters of similar cells were found as much as 1 millimeter below the stratum granulosum. There is a fibrous reaction and a lymphocyte reaction. Note the large size of the cells in the junctional and intradermal clusters.

A high power view of the dermis. In addition to the large clusters shown above, there are smaller clusters of atypical cells that are separated by delicate delicate collagen. Mitoses are significant in the dermal portion of a melanocytic lesion but much less so in the intraepidermal portion of a melanocytic lesion.

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	Very low power view (direct scan of glass slide). This profile of this melanoma is relatively symmetrical.
	A high power view of the epidermis. Pagetoid melanocytes (PM) are in the stratum granulosum. Atypical junctional melanocytes are found in a cluster that has been cut off in the right side of the picture.
	A medium power view of the lower epidermis as well as papillary dermis. Clusters of similar cells were found as much as 1 millimeter below the stratum granulosum. There is a fibrous reaction and a lymphocyte reaction. Note the large size of the cells in the junctional and intradermal clusters.
	A high power view of the dermis. In addition to the large clusters shown above, there are smaller clusters of atypical cells that are separated by delicate delicate collagen. Mitoses are significant in the dermal portion of a melanocytic lesion but much less so in the intraepidermal portion of a melanocytic lesion.