HUMAN PARATHYROID-HORMONE RELATED PROTEIN IN OVARIAN SMALL-CELL CARCINOMA - AN IMMUNOHISTOCHEMICAL STUDY

Background. Small cell carcinomas (SCC) are the most common ovarian tu mors associated with hypercalcemia. Parathyroid hormone-related protei n (PTHrp) is the most frequent cause of hypercalcemia of malignancy. M ethods. The presence of PTHrp in SCC has been studied by immunohistoch emistry in formalin fixed, paraffin embedded tissues. A polyclonal ant ibody against a synthetic peptide corresponding to the first 36-N term inal amino acid residues of PTHrp was used. Normal dog skin, which is rich in PTHrp, was used as a positive control. Absorption tests using the synthetic peptide as antigen were done in all the cases. Results. Immunoreactivity for PTHrp was found in five of seven cases of SCC. Th e serum calcium levels were elevated in two of these cases, normal in two, and unknown in one. The two negative cases were associated with h igh serum calcium levels. Conclusion. The lack of correlation between immunoreactivity and serum calcium levels can be explained on the basi s that immunohistochemistry is dependent on the peptide content of cel ls rather than on the capability for hormone production and/or release . The results suggest that PTHrp plays a role in the development of hy percalcemia in patients with SCC of the ovary.