Methodology: IHC

Clinical Significance:
Identifies: The gp100 protein, found in premelanosomes.  As such, HMB-45 is a highly sensitive and specific marker of melanoma, particularly in the metastatic setting.  The epitope targeted by HMB-45 behaves as an ‘oncofetal’ antigen that is not expressed in normal, resting melanocytes but is present in reactive and neoplastic melanocytic processes. Furthermore, as a marker of a premelanosomal protein, it is also an excellent marker of clear cell sarcoma as well as PEComas. Subcellular Localization: Cytoplasmic, granular

Organ: Skin & Mucosa

Disease State: Large Cell Undifferentiated Malignant Neoplams

CPT Code(s): 88342 or 88341 (reference only; CPTs may vary)

Turnaround Time: Within 1-2 business days of receipt

Schedule: Monday - Friday

Specimen Requirements:
• Formalin-fixed, paraffin-embedded (FFPE) tissue block or cell block - OR - • 1 unstained slide for each test requested plus 3-4 additional unstained slides cut at 4µm