alexa Expression of Melan-A and Ki-67 in desmoplastic melanoma and desmoplastic nevi.
Dermatology

Dermatology

Dermatology and Dermatologic Diseases

Author(s): Kucher C, Zhang PJ, Pasha T, Elenitsas R, Wu H, , Kucher C, Zhang PJ, Pasha T, Elenitsas R, Wu H,

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Abstract BACKGROUND: Desmoplastic melanoma (DMM) is an uncommon melanoma variant with a distinct morphology, including a prominent spindle cell component with fibrosis, as well as a distinct immunohistochemical profile. Histologically, the spindle cell component of DMM can be confused with sclerotic/desmoplastic nevi, nonpigmented blue nevi, scar, and neural tumors. The histological distinction between sclerotic/desmoplastic/blue nevi and DMM using standard light microscopic techniques can be exceedingly subtle. Therefore, we investigated whether immunohistochemical staining for Melan-A and Ki-67 expression can be used to discriminate these lesions, distinguishing between epithelioid and spindle cell compartments of the lesions. DESIGN: Fifty cases of DMM and 13 cases of sclerotic/desmoplastic/blue nevi were identified. Standard immunohistochemical techniques were used with antibodies towards HMB-45, Melan-A (A103), and Ki-67; 43 of 50 DMM cases were available for staining with Melan-A, 42 of 50 for HMB-45, and 31 of 50 cases were stained with Ki-67. All 13 nevi were stained for Melan-A and 8 for Ki-67. Immunoreactivity to Ki-67 antibody was scored as 0 to 5\%, 6 to 10\%, 11 to 30\%, or greater than 30\% positive tumor cells. RESULTS: Only 3 of 43 and 3 of 42 of spindle cell compartments of DMMs were positive for Melan-A and HMB-45, respectively. Focal staining of epithelioid cells in the junctional component or superficial dermis was observed in 33\% (14/43). In contrast, 100\% of the 13 nevi were strongly positive for Melan-A (P < 0.001). Seventeen melanomas (55\%) were 0 to 5\% positive for Ki-67, five (16\%) fell into the 6 to 10\% category, three (10\%) were between 11 and 30\%, and six (19\%) were at least focally greater than 30\% positive. All 8 nevi (100\%) had less than 5\% positive cells for Ki-67 (P = 0.02), with only 2 cases having more than 2\% positive cells. CONCLUSION: The sclerotic/desmoplastic and hypopigmented blue nevi were uniformly positive for Melan-A, while the vast majority of DMM were negative in their spindle cell compartments. Melan-A is very useful in distinguishing between DMM and sclerotic nevi. Ki-67 appears to be an inconsistent marker for DMM. However, a high labeling index (over 5\%) may be used as a clue in diagnosing DMM.
This article was published in Am J Dermatopathol and referenced in Dermatology and Dermatologic Diseases

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