Anti-alpha 1-antichymotrypsin staining of 194 sarcomas, 38 carcinomas, and 17 malignant melanomas. Its lack of specificity as a tumour marker.

A polyclonal commercially available antiserum to alpha 1-antichymotrypsin (alpha 1ACT) was reacted with 194 sarcomas, 38 carcinomas, and 17 malignant melanomas; 61 of 194 sarcomas, 14 of 38 carcinomas, and 10 of 17 malignant melanomas reacted positively. Thirteen categories of sarcomas were examined. All but one group (haemangiopericytomas) showed positively staining tumour cells. Malignant fibrous histiocytomas, angiosarcomas, and Kaposi's sarcomas showed positive staining in over 70% of tumours. All categories of carcinomas examined, with the exception of transitional cell carcinomas, stained positively. The results of this study suggest that the use of alpha 1ACT antiserum is of little value in the differential diagnosis of either sarcomas or carcinomas, nor can it be used as a specific histiocytic marker.