The Significance of immunohistochemical markers when evaluating thickness of cutaneous melanoma and melanocytic nevi

Abstract

Introduction Survival and treatment of cutaneous melanoma (CM) depends on the Breslow depth (BD) of the tumour measured during histological examination. Routinely the thickness of CM is estimated in histological sections stained with haematoxylin and eosin (HE) and less frequently using immunohistochemical (IHC) markers. The aim of the study was to compare the BD of melanocytic skin tumours (MST) measured in histological samples stained with HE, IHC marker S100, and a mixture of monoclonal antibodies (MMA), including HMB-45, Melan-A, and tyrosinase. Materials and methods Excised 59 CM and 87 melanocytic nevi (MN) were prospectively included in the study. Formalin-fixed and paraffin-embedded sections of MST showing the greatest BD were stained with HE, S100, and MMA. Tumour thicknesses in samples stained with HE – BD (HE), S100 – BD (S100), and MMA – BD (MMA) were measured by two observers. If the difference between BD (HE) and BD (S100) or BD (MMA) was <0.1 mm complete agreement between values were recorded. Lymphocytic infiltrate (absent or mild, moderate, or pronounced) and its predominant location (stroma or the surrounding of the tumour), dermal melanophages (absent or several, moderate, or abundant), periadnexal extension of the melanocytes, and small clusters or isolated dermal melanocytes were evaluated in all the samples. Median and interquartile range (in parentheses) of BD values were calculated. The logistic analysis was performed to identify the odds ratio (OR) of semi-quantitative histological findings for the disagreement between BD (HE) and BD detected with IHC markers, comparing with the complete agreement of BD values. Results Median BD in HE, S100 and MMA samples were accordingly 0.7 (0.46-1.055) mm, 0.7 (0.49-1.13) mm, 0.69 (0.48- 1.06) mm in MN cases and 0.97 (0.61-1.62) mm, 0.96 (0.6-1.43) mm, 0.92 (0.59-1.38) mm in CM cases. Bland – Altman revealed statistically significant difference between BD (HE) and BD (S100) (mean differen