Alpha-1-Antichymotrypsin Primary Antibody reacts with histiocytes and histiocytic neoplasms. Its major application is defining the presence of Alpha-1-Antichymotrypsin in histiocytes and tumors derived from them. In eosinophilic granuloma and malignant histiocytosis, the reaction for this marker is heterogeneous in intensity and distribution. In fibrous histiocytomas on the other hand, a diffuse homogeneous reaction may be observed. Acinar tumors of the pancreas and salivary gland may also exhibit Alpha-1-Antichymotrypsin positivity.