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Skin-Melanocytic Tumors
Last major update: November 2008 - next update November 2009
Revised: 26 October 2009
Author: Nat Pernick, M.D., PathologyOutlines.com, Inc.
Copyright: (c) 2002-2009, PathologyOutlines.com, Inc.
Definition
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● First descried by Reed (Semin Oncol 1975;2:119)
● Controversial topic - concept is not universally accepted
● Introduced to embrace the concept that a subset of invasive melanomas is characterized by lesser cytologic atypia and a better prognosis than conventional melanomas of the same thickness
● Cells are more atypical than nevi but less atypical than classic melanoma
Terminology
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● Also called borderline melanocytic lesion
Epidemiology
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● Usually on trunk of adults in 20’s and 30’s (Cancer Treat Rev 2002;28:219)
Treatment and prognosis
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● Better prognosis than other melanomas, even with infiltration of reticular dermis (Hum Pathol 1986;17:796)
Clinical description
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● Plaque or nodule, fleshy, dark brown or blue-black, up to 1 cm
● May resemble an epidermal cyst
Micro description
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● Expansive nodule in vertical growth phase that fills papillary dermis and may extend into reticular dermis
● Usually uniform cells with mild to moderate atypia that resemble nevus cells but are moderately enlarged with irregular chromatin and increased N/C ratios
● Growth displaces surrounding structures and remnants of residual benign nevus are often present
● Equivalent to at least a level III melanoma due to extent of dermal invasion
● May have perineural invasion and mitotic figures, but usually does not invade subcutaneous fat; no necrosis, no maturation
● Variants: Spitz, halo nevus-like (Am J Surg Pathol 1990;14:53), spindle cell (Pediatr Pathol 1988;8:401), desmoplastic, small cell, dermal
Micro images
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Nodular tumor filling papillary dermis Halo variant Ki-67 in this (Fig C) and
other melanocytic lesions
Positive stains
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● Ki-67 and p53 values are intermediate between compound or Spitz nevi and superficial spreading melanoma (Mod Path 2003;16:525)
Differential diagnosis
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● Nevoid melanoma - more mitotic figures, usually no residual nevus
Additional references
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● Mod Path 2006;19 Suppl 2:S41
End of Skin-Melanocytic Tumors > Minimal deviation melanoma
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