Differentiating regressed melanoma from regressed lichenoid keratosis

• Published in: Journal of cutaneous pathology 2017-04, Vol.44 (4), p.338-341
• Main Authors: Chan, Aegean H., Shulman, Kenneth J., Lee, Bonnie A.
• Format: Article
• Language: English
• Subjects: benign lichenoid keratosis; Cytokeratin; Dermis; Diagnosis, Differential; Epidermis; Female; Humans; Inflammation; Keratinocytes; Keratosis; Keratosis - metabolism; Keratosis - pathology; Lichen planus; Lichenoid Eruptions - metabolism; Lichenoid Eruptions - pathology; lichenoid keratosis; Male; Melanocytes; Melanoma; Melanoma - metabolism; Melanoma - pathology; Microphthalmia-associated transcription factor; regression; Skin; Skin Neoplasms - metabolism; Skin Neoplasms - pathology
• ISSN: 0303-6987; 1600-0560
• DOI: 10.1111/cup.12879

Background Distinguishing regressed lichen planus‐like keratosis (LPLK) from regressed melanoma can be difficult on histopathologic examination, potentially resulting in mismanagement of patients. Objective We aimed to identify histopathologic features by which regressed melanoma can be differentiated from regressed LPLK. Methods Twenty actively inflamed LPLK, 12 LPLK with regression and 15 melanomas with regression were compared and evaluated by hematoxylin and eosin staining as well as Melan‐A, microphthalmia transcription factor (MiTF) and cytokeratin (AE1/AE3) immunostaining. Results (1) A total of 40% of regressed melanomas showed complete or near complete loss of melanocytes within the epidermis with Melan‐A and MiTF immunostaining, while 8% of regressed LPLK exhibited this finding. (2) Necrotic keratinocytes were seen in the epidermis in 33% regressed melanomas as opposed to all of the regressed LPLK. (3) A dense infiltrate of melanophages in the papillary dermis was seen in 40% of regressed melanomas, a feature not seen in regressed LPLK. Conclusions In summary, our findings suggest that a complete or near complete loss of melanocytes within the epidermis strongly favors a regressed melanoma over a regressed LPLK. In addition, necrotic epidermal keratinocytes and the presence of a dense band‐like distribution of dermal melanophages can be helpful in differentiating these lesions.