Immunohistochemistry in Dermatopathology: Common Stains

Overview / Definition Immunohistochemistry (IHC) is a laboratory technique used to identify specific proteins in tissue sections by employing antibodies that bind to the target antigens. In dermatopathology, IHC plays a crucial role in differentiating between various skin lesions, including malignant and benign tumors, inflammatory conditions, and infectious diseases. Epidemiology The utilization of IHC in dermatopathology is prevalent in many clinical settings, especially in the diagnosis of skin cancers. The most commonly analyzed skin cancers include: Melanoma Basal cell carcinoma (BCC) Squamous cell carcinoma (SCC) With the increasing incidence of skin cancers globally, the demand for accurate diagnostic techniques like IHC is also rising. Pathophysiology / Mechanism IHC works by exploiting the principle of antigen-antibody binding. Specific antibodies are applied to fixed tissue sections, where they bind to their corresponding antigens. This is followed by the application of a secondary antibody, usually conjugated to an enzyme or a fluorescent dye, which allows visualization under a microscope. The key steps in the IHC process include: **Fixation**: Preserving tissue morphology **Embedding**: Infiltrating tissue with paraffin **Sectioning**: Cutting thin tissue slices for staining **Deparaffinization**: Removing paraffin to allow antibody penetration **Blocking**: Reducing nonspecific binding **Staining**: Applying primary and secondary antibodies Clinical Presentation The clinical presentation of skin lesions may vary significantly, and this necessitates the use of IHC for accurate diagnosis. Common presentations include: Melanoma: Asymmetrical, irregularly shaped lesions with color variegation. Squamous cell carcinoma: Crusted, scaly lesions that may be painful. Basal cell carcinoma: Pearly nodules or non-healing ulcers. Diagnosis / Workup The diagnosis of skin lesions using IHC involves the following steps: **Clinical evaluation**: Assessing patient history