Assessment of the immunoreactivity of the junctional, superficial and deep dermal components of melanocytic skin lesions has a limited role in their differential diagnosis. Ki-67 is useful in distinguishing melanomas (including nevoid, desmoplastic and metastatic) from naevi. Expression of HMB-45 in the deep component of malignant melanomas distinguishes them from compound naevi, Spitz naevi and dysplastic naevi, all of which show negativity of the deep component. Interpretation of an apparent maturational gradient in both morphology and immunoreactivity is made more difficult by the existence of malignant melanomas with paradoxical maturation1:
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compound naevi (CN) |
conventional malignant melanoma (MM) |
invasive melanoma with paradoxical maturation (IMP) |
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diffuse staining of superficial and deep components of all groups (compound naevi show more staining of their deep component than do invasive melanoma with paradoxical maturation) |
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reduced expression with increasing depth |
expression does not decrease with increasing depth. Greater expression in the deep component than for IMP |
reduced expression in the deep component. Greater expression at both superficially and deeply than naevi. |
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reduced expression with increasing depth
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expression does not decrease with increasing depth. Greater intensity of expression in the deep component than for IMP
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reduced expression in the deep component. similar degree of expression both superficially and deeply to naevi.
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maturational gradient: decreased numbers of cells staining with increasing depth |
No maturational gradient |
maturational gradient: decreased numbers of cells staining with increasing depth. The proportion of cells at each depth which are positive is intermediate between the numbers for naevi and conventional melanoma |
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References
1SM Ruhoy et al. Malignant melanoma with paradoxical maturation. Am J Surg Pathol 2000;1600-1614.
This page last revised 18.4.2001.
©SMUHT/PW Bishop