The basic chromospheres of skin that might not be differentiated visually: Observations on aneurysmal fibrous histiocytomas and malignant melanomas

Aim: Aneurysmal fibrous histiocytoma (AFH) is a variant of fibrous histiocytoma, which has a cleft-like cavernous blood-filled space in the tumor. It appears as a single reddish black tumor with variable levels of pain and size from its bleeding. And, it must be differentiated from other similar looking malignant conditions such as malignant melanoma. The visual mimicry of AFH to melanoma was raised by some careful dermatologists, but never be confirmed objectively by colorimetric analysis. Materials, Subjects, and Methods: In this study, we simply analyzed conventionally photographed digital images of thirty-seven cases of fibrous histiocytomas, including three AFH cases into colorimetrically useful color space, CIELAB, of which coordinates are L*, a*, and b* representing lightness, red to green, and yellow to blue axis, respectively. In addition, we also analyzed the clinical digital images of seven cases of malignant melanomas. Using statistical package, each coordinates of CIELAB were compared using Wilcoxon rank sum test between AFH and melanomas. The CIELAB coordinates of AFH and non-aneurysmal fibrous histiocytomas were compared statistically as well. Results: Comparing with banal fibrous histiocytomas, the colors of AFH showed significantly smaller a* and b* coordinates (P = 0.008, 0.008, respectively), which implies more green and blue hue of AFH lesion. Rather, they were more like melanomas (P = 0.2839, 0.2040, respectively). As for L*, there were no significant differences for all comparisons. Conclusions: As a result, more objective analysis of the digital images using colorimetric color space confirmed the visual mimicry of AFH to melanoma.