Nerve Fiber Immunohistochemical Panel Discriminates between Nerve Sheath and Perivascular Wall Tumors

SIMPLE SUMMARY: Soft-tissue sarcomas are classified as nerve sheath tumors if originating within nerves. However, tumors of the nerves still pose a frequent challenge for diagnostic veterinary pathologists since identifying nerve histomorphology based only on the examination of hematoxylin-and-eosin-stained sections is often insufficient. In addition, there are no robust tumor-related biomarkers for a reliable diagnosis of nerve sheath tumors. Improving the anatomo-pathological diagnosis of nerve sheath tumors will contribute to a more accurate classification of soft-tissue sarcomas and their prognosis, ultimately aiding clinicians in making informed decisions for their patients. This current immunohistochemical study explores a combined panel of laminin, Sox-10 and periaxin-1 as an ancillary diagnostic approach to confirm the diagnosis of suspect nerve sheath tumors. The study demonstrates that this panel discriminates reliably between soft-tissue subtypes such as nerve sheath tumors and perivascular wall tumors. ABSTRACT: Benign and malignant nerve sheath tumors (NST) pose a major challenge in routine diagnostic anatomic pathology because of shared histomorphological features with other soft-tissue tumors (STT). As a result, NST are often diagnosed as STT, a broad category that encompasses various entities including perivascular wall tumors (PWT) and that represents approximately 15% of all skin tumors in dogs. Immunohistochemistry (IHC) can assist the identification of histologic subtypes of STT. This IHC pilot study applies various markers largely expressed by peripheral nerves to twelve benign and six malignant NST and determines the intratumoral protein expression of laminin, periaxin-1, Sox-10 and S-100 in the NST subtypes. Furthermore, this study assesses the usefulness of peripheral nerve markers applied to diagnostic work cases and demonstrates the relevance of laminin expression patterns, periaxin-1 and Sox-10 in assisting the differentiation of NST from other STT, in particular from PWT.