Expression of matrix metalloproteinase gelatinase A messenger ribonucleic acid in parathyroid carcinomas

The incidence of parathyroid cancer in patients with hyperparathyroidism is less than 1%. However, these few cases cause diagnostic problems in the absence of clear-cut invasion of adjacent organs or metastasis. New markers are needed to increase diagnostic accuracy.

Thirty-one parathyroid tumors from patients with primary hyperparathyroidism were collected worldwide. Eighteen tumors were classified as unequivocal cancers, whereas 13 tumors were considered equivocal because of a lack of infiltrative growth or evidence of recurrence. Paraffin sections were hybridized with a 35S-labeled riboprobe complementary to gelatinase A mRNA, dipped in photographic emulsion, developed, counterstained, and then evaluated by light- and dark-field microscopy.

Fourteen of the 18 unequivocal parathyroid cancers expressed gelatinase A, as compared with the equivocal tumors, of which only 4 of 13 showed expression. The strongest hybridization signal was seen in stromal cells at the tumor border, most likely fibroblasts and macrophages. No expression was detected in tumor cells.

Invasive growth of many tumors is facilitated by proteolytic enzymes, such as gelatinase A. The presence of gelatinase A mRNA in parathyroid tumors strengthens the suspicion of malignancy but cannot be used as a definitive marker of malignancy.