Observation of Chrysalis Structures With Polarized Dermoscopy

Collagen bundles have birefringent properties that cause a rapid randomization of polarized light, explaining why collagen is more conspicuous under polarized dermoscopy.¹ Skin lesions with an increased amount of collagen will often reveal shiny, bright white, orthogonal linear streaks, which we have termed “chrysalis structures.” These structures are not apparent to the unaided eye nor are they visible with nonpolarized dermoscopy. The most obvious examples of lesions that display chrysalis structures are dermatofibromas (Figure 1)^{2 - 3} and scars. In basal cell carcinoma, chrysalis structures are often observed, probably owing to the associated fibroplasia (Figure 2).^{4 - 5} In addition, chrysalis structures are seen on occasion in Spitz nevi (Figure 3 [courtesy of Harold Rabinovitz, MD, Skin and Cancer Associates, Plantation, Florida]) and in melanoma (Figure 4), probably corresponding to changes in the composition and orientation of collagen in the stroma that underlies these melanocytic neoplasms.^{6 - 8} Interestingly, it has been suggested that collagen remodeling in the stroma of melanoma is important for the invasion of tumor cells into the dermis.⁹

Polarized dermoscopy can also be used in a dynamic fashion. Rotating the polarized dermoscope while keeping the eye (or attached camera) stationary will cause the chrysalis structures to appear more or less prominent depending on the angle of polarization (a video is here). This phenomenon is called angular dependence of polarized light and probably reflects the nonrandom orientation of collagen in the dermis. Dynamic polarized dermoscopy is a simple optical maneuver to validate the presence of chrysalis structures in lesions.