The Histopathologic Evaluation of Diagnostic Procedures in Nail Melanoma

Abstract

Introduction: The diagnostic delay in nail melanoma (NM) has been repeatedly emphasized. It may be related to both clinical misinterpretations and to errors in the bioptic procedure.

Objectives: To assess the efficacy of histopathologic examination in different diagnostic biopsies in NM.

Methods: We retrospectively investigated the diagnostic procedures and histopathologic specimens referred to the Laboratory of Dermatopathology for the clinical suspicion of NM from January 2006 to January 2016.

Results: Eighty-six nail histopathologic specimens were analyzed consisting in 60 longitudinal, 23 punch and 3 tangential biopsies. A diagnosis of NM was performed in 20 cases, benign melanocytic activation in 51 cases and melanocytic nevi in 15 patients. Longitudinal and tangential biopsy were diagnostic in all cases, regardless of the clinical suspicion. Nail matrix punch biopsy instead was not diagnostic in most of the cases (13/23 specimens).

Conclusions: In the presence of an NM clinical suspicion, longitudinal biopsy is recommended (lateral or median) because it provides exhaustive information on the characteristics of melanocytes morphology and distribution in all the components of the nail unit. Tangential biopsy, recently encouraged by expert authors due to the optimal surgical outcome, in our experience gives incomplete information on tumor extension. Punch matrix biopsy gives limited evidence in the diagnosis of NM.

Figure 1

(A, B) Nail melanoma: histopathologic aspects of a nail matrix biopsy (H&E original magnification 10X; 25X) showing proliferation of atypical melanocytes in the basal and supra-basal layers of the nail matrix.

Figure 2

(A, B) Benign melanocytic activation: histopathologic aspects of a longitudinal nail biopsy (H&E original magnification 20X; 25X) showing proliferation of melanocytes in the nail matrix and nail bed.