Melanoma mimicking Rosai‐Dorfman disease

Abstract

Despite well-defined clinical and histopathological features of melanoma, atypical presentations mimicking other skin disorders can result in a delayed diagnosis or misdiagnosis and subsequent inappropriate treatment. Rosai-Dorfman disease (RDD) is a rare histiocytic disorder with unique clinical and histopathological features. We report a case of melanoma treated with cryotherapy that mimicked RDD both clinically and histopathologically. We compare this RDD-like melanoma to classic RDD, outlining the importance of clinicopathological correlation prior to treatment, as well as the potential pitfalls in diagnosis after cryotherapy of pigmented lesions.

Histiocytoid melanoma: Diagnostic pitfall and mimicker of non‐Langerhans cell histiocytoses including reticulohistiocytoma

“…Immunohistochemistry would still be useful to confirm a putative melanoma diagnosis even when an in situ component is identified because a case of epidermotropic xanthogranuloma has been reported 10 . Neither the previous case of melanoma mimicking Rosai–Dorfman disease 11 nor our case of melanoma resembling reticulohistiocytoma had an intraepidermal component. Both cases did however show emperipolesis.…”

“…The mechanism by which melanoma histopathologically resembles reticulohistiocytoma, xanthogranuloma, and Rosai–Dorfman disease is unknown. The Rosai–Dorfman‐like lesion had previously been treated with cryotherapy, which is known to induce bizarre changes in common nevi and was posited as a potential explanation for the unusual appearance 11 . Other considerations include a phenomenon akin to balloon cell change in nevi and melanoma.…”

“…The Rosai-Dorfman-like lesion had previously been treated with cryotherapy, which is known to induce bizarre changes in common nevi and was posited as a potential explanation for the unusual appearance. 11 Other considerations include a phenomenon akin to balloon cell change in nevi and melanoma. Electron microscopy performed on these lesions has shown intracytoplasmic vacuoles, which could represent an accumulation of enlarged, degenerative melanosomes, 17,18 a mechanism that has received further acknowledgement in the more recent literature.…”

Histiocytic and dendritic cell neoplasms of the mediastinum

“…It is these cases where a low threshold for S100 and/or cyclin D1 staining, and even molecular analysis in search of MAPK pathway related mutations can be critical or even necessary for the diagnosis. Remembering that RDD cells are typically SOX10 negative despite strong S100 expression is also useful given that melanoma should always be considered in the differential diagnosis of a histiocytoid neoplasm with a rich lymphoplasmacytic infiltrate ( 6 ). In contrast to RDD, melanoma typically exhibits both SOX10 and S100 expression, with the former often stronger and more diffuse.…”