Morphologic Features of Melanophages Under in Vivo Reflectance Confocal Microscopy

Objectives: 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.

Design: Consecutive retrospective study.

Setting: Referral center for pigmented lesions.

Patients: 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.

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

Results: 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).

Conclusion: 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.