Immunohistochemistry Update in Dermatopathology and Bone and Soft Tissue Pathology

CONTEXT.—: Immunohistochemistry plays an important role in dermatopathology, particularly for melanocytic lesions and poorly differentiated malignancies. In the field of bone and soft tissue pathology, molecular methods remain the gold standard for diagnosis; however, immunohistochemistry targeting underlying molecular alterations represents a valuable screening tool, especially in areas with limited access to molecular testing. OBJECTIVE.—: To describe the utility and limitations of new and emerging immunohistochemical stains in the diagnosis of skin, soft tissue, and bone tumors. DATA SOURCES.—: A literature review of recently described immunohistochemical stains in the fields of dermatopathology and bone and soft tissue pathology was performed. CONCLUSIONS.—: Immunohistochemistry is an important adjunctive tool for select entities in dermatopathology and bone and soft tissue pathology, and it provides pathologists with valuable evidence of their behavior, underlying molecular alterations, and line of differentiation. Furthermore, immunostains targeting molecular abnormalities have the potential to replace current molecular methods. Many of these recently described stains demonstrate higher sensitivity and specificity; however, limitations and pitfalls still exist, and correlation with morphologic and clinical findings remains essential for diagnosis.