Morphologic features of melanophages under in vivo reflectance confocal microscopy

To determine morphologic features of melanophages under in vivo reflectance confocal microscopy (RCM) and to highlight morphologic features that are important in distinguishing melanophages from melanocytes.

Consecutive retrospective study.

Referral center for pigmented lesions.

The study group retrospectively constituted 20 consecutive patients having biopsy-proven lichen planus-like keratoses that dermoscopically and histopathologically showed many melanophages and that had been imaged under RCM before biopsy.

The RCM characteristics of isolated dermal bright cells were scored blinded to dermoscopic features and histopathologic diagnosis.

Under RCM, melanophages were significantly smaller than melanocytes (mean [SD] cell diameter, 13.6 [1.6] vs 18.2 [2.9] microm, P = .006). Nuclei (intracellular low-reflectance round-oval structures) were visible in only 16% (29 of 184) of the cells in melanophages vs 57% (28 of 49) of the cells in melanocytes (P < .001). When identified, nuclei were smaller in melanophages than in melanocytes (mean [SD] diameter, 3.2 [1.2] vs 6.4 [0.7] microm, P < .001). Compared with melanocytes, melanophages were significantly more ill defined (76% [140 of 184] vs 18% [9 of 49], P < .001), less round (23% [42 of 184] vs 69% [34 of 49], P < .001), and less dendritic (1% [2 of 184] vs 12% [6 of 49]) (P = .001).

Observed differences in morphologic features should enable distinction between melanophages and melanocytes under RCM, thereby improving the accuracy of skin lesion diagnosis using this technique.