Histomorphological Spectrum and Diagnostic Utility of S100, SOX10, CD34, Calretinin, and Ki67 in the Evaluation of Schwannomas: A Retrospective Study of 26 Cases in a Tertiary Health Institute, Zaria-Nigeria.

Background: Schwannomas, also known as neurilemmomas, are benign nerve sheath tumours derived from Schwann cells. Schwannomas are truly encapsulated, slow-growing tumours with a very wide anatomical distribution but with a predilection for the extremities and head and neck regions. The study aimed to analyse the histomorphological spectrum and diagnostic utility of immunohistochemistry in schwannomas. The frequency distribution and demographic characteristics of these tumours were also determined. Materials and Methods: This was a 10-year hospital-based retrospective study of all cases of schwannomas that strictly met the inclusion criteria. Patients' records and tissue blocks were retrieved from archives. Formalin-fixed paraffin-embedded tissue blocks were subjected to histochemical and immunohistochemical analysis following standard protocols, and the slides produced were reviewed and interpreted. Collated data were analysed and depicted using statistical charts and tables. Results: Twenty-six cases were seen which occurred more in females with a male-to-female ratio of 1:1.2. The most frequent decade of occurrence was the fourth decade of life, and the upper limb was the most frequent anatomical site of occurrence with few cases seen in unusual sites. The most frequent histological variant seen was the conventional type, constituting 14 cases (53.8%). SOX10 showed 96% immunopositivity, calretinin showed 96% immunopositivity, and S100 showed 81% immunopositivity with varying staining intensities. CD34 antibody showed 73% immunopositivity which was mainly seen in the Antoni B areas. Ki67 antibody was not expressed in any of the cases subjected to it. Conclusion: Histomorphology and immunohistochemistry are valuable tools in the definitive diagnosis of schwannomas.