Factor XIIIa has been identified in platelets, megakaryocytes, and fibroblast-like mesenchymal or histiocytic cells in the placenta, uterus, and prostate, monocytes and macrophages and dermal dendritic cells. Anti-Factor XIIIa has been found to be useful in differentiating between dermatofibroma (almost all cases are positive), dermatofibrosarcoma protuberans (-/+) and desmoplastic malignant melanoma (-). Anti-Factor XIIIa positivity is also seen in capillary hemagioblastoma, hemangioendothelioma, hemangiopericytoma, xanthogranuloma, xanthoma, hepatocellular carcinoma, glomus tumor, and meningioma.

Store the Factor XIIIa antibody at 2-8°C (with azide) or aliquot and store at -20°C or colder (without azide).