悪性黒色腫早期病変の疑診例

抄録

A 29-year old man noticed a small bluish-brown spot on his right knee about 3 months ago. In the last 2 weeks it has suddenly enlarged, darkened and taken irregular shape. It was 3mm in diameter, black, having elevated macule with slight irregularity at the margin.
Histopathological findings showed the lesion to be asymmetrical with unsharp lateral margins and mild inflammatory infiltrates in the upper dermis. Epidermis wasslightly acanthotic and there were tumor cells with atypical nuclei nested and scattered not only in the mid and lower epidermis but also up to the granular layer with casting off of melanocytes and melanin. The nests were of irregular sizes and shapes, not equidistant and tended to coalesce with a few mitoses. Therefore, we strongly suspected a malignant melanoma in situ in spite of it's very small size, although there was disagreement among the commentators.