๐ ็ธฝ็ฎ้ ๏ฝ ๐ ่ฑๆๅๆ๏ผๆฌ็ฏ๏ผ ๏ฝ ๐ ๅฎๆด็ฟป่ญฏ ๏ฝ โญ ็ฒพ่ฏ็ญ่จ
Nested melanoma
Nested melanoma
This is a rare, recently described distinctive type of melanoma described as a variant of superficial spreading melanoma.1,2 It presents in middle-aged to elderly adults with the same sex incidence. Although the clinical features are usually suspicious of melanoma, the histologic appearances are misleading. Tumors are in-situ or invasive and the junctional component is distinctively nested with little or no proliferation of melanocytes between the nests. The latter may be confluent and are located at the tips or less commonly, the slopes of the rete-ridges. Mitotic activity tends to be low within the nests and cytologic atypia varies from moderate to severe. Multiple chromosomal abnormalities are demonstrated by cytogenetic analysis.
Loss of p16 protein expression correlates with invasive and metastatic melanoma.96โ99 It has also been shown to correlate with increased Ki-67 immunolabeling and independently to predict a poor prognosis.70,98 P16 may also be helpful in differentiating capsular nevus from metastatic melanoma in sentinel lymph nodes.100,101
Although mutation of the TP53 gene is relatively uncommon in melanoma at around 20%, overexpression of p53 protein may be identified in up to 40% of cases of invasive and metastatic melanoma, perhaps indicating disruption of this pathway.102โ107 It may therefore be of value in distinguishing between nevi (banal and Spitz) and melanoma. The former show virtually no positive cells whereas in the nodular and to a lesser extent superficial spreading melanoma they may be conspicuous. Expression of p53 also appears to be an independent predictor of poor prognosis.68,106,108