Comprehensive Histopathologic Comparison of Epidermotropic/Dermal Metastatic Melanoma and Primary Nodular Melanoma

Abstract

Aims

Metastatic melanoma involving the epidermis and/or upper dermis may show significant histologic overlap with primary cutaneous melanoma, especially the nodular subtype. Proper histopathologic classification is crucial to appropriate staging and management, yet often challenging. This study aims to identify helpful histopathologic features in differentiating epidermotropic/dermal metastatic melanoma (EDMM) and primary nodular melanoma (PNM).

Methods and Results

A cohort of EDMM (n=74) and PNM (n=75) was retrospectively reviewed for various histopathologic features, and the data were compared between groups by univariate analysis. Features significantly associated with EDMM included tumor size of <0.2 cm, absence of tumor-infiltrating lymphocytes and plasma cells, monomorphism, and involvement of adnexal epithelium. Features associated with PNM included polypoid (exophytic) configuration, prominent tumor-infiltrating plasma cells (TIPs), tumor size of >1 cm, ulceration, epidermal collarette, higher mitotic rate, necrosis, multiple phenotypes, significant pleomorphism, and lichenoid inflammation. By multivariate analysis, a logistic regression model including large tumor size, ulceration, prominent TIPs, lichenoid inflammation, and epidermal collarette was highly predictive of PNM. Six (8%) EDMM cases from three patients demonstrated an "epidermal-only" or "epidermal-predominant" pattern closely simulating in-situ or microinvasive melanoma. Two of these cases were tested by fluorescence in situ hybridization which confirmed clonal relationship with their corresponding primary melanomas.

Conclusions

This is the first comprehensive histopathologic comparison of EDMM and PNM. Recognition of the above histopathologic associations should aid in correct classification and staging of cutaneous melanoma. Epidermotropic metastatic melanomas may occasionally display an epidermal-only/predominant pattern; accurate diagnosis requires prudent clinical correlation and, when necessary, ancillary molecular tests.

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from #ORL-AlexandrosSfakianakis via ola Kala on Inoreader http://ift.tt/2xclwKU