Identification of primary tumour site by immunolocalization of progastricsin in metastatic adenocarcinoma.

The aspartic proteinase zymogen, progastricsin, which occurs in normal gastroduodenal mucosa and prostate, has been localized by the immunogold-silver method in formalin-fixed, paraffin-embedded sections of metastatic adenocarcinoma in lymph nodes and liver, the primary site being known in each case. Progastricsin was demonstrated in 16 of 84 lymph node metastases, including 7 of 17 from stomach, 2 of 2 from prostate, and 7 of 65 from other sites. Progastricsin was also found in 19 of 98 hepatic metastases, including 8 of 22 from stomach, 6 of 24 from pancreas, and 5 of 52 from other sites. The presence of progastricsin in a metastasis correlated well with a primary tumour in the stomach or prostate or, less significantly, pancreas. Immunolocalization of progastricsin in a histological section of metastatic adenocarcinoma may help to locate the primary site.