Prostatic acid phosphatase in strumal carcinoids of the ovary. An immunohistochemical study

Background. Strumal carcinoids (SC) are ovarian tumors containing thyroid parenchyma admixed with carcinoid elements. Microscopically, the carcinoid component of SC usually presents a ribbon or trabecular pattern similar to the pattern exhibited by hindgut carcinoids. The authors designed an immunohistochemical study to ascertain further similarities of the carcinoid component of SC to rectal carcinoids. Methods. Five cases of SC were examined by light microscopic study with hematoxylin and eosin and immunoperoxidase staining with a group of neurohormonal peptides, thyroglobulin, prostatic acid phosphatase, and prostate specific antigen. Results. All tumors were positive for thyroglobulin, chromogranin, prostatic acid phosphatase (PAP), and glucagon. They were consistently negative for prostate specific antigen and variably positive to the other antibodies. Conclusions. The consistent positivity of the carcinoid component of SC to PAP immunostaining is a further similarity of these tumors to rectal carcinoids, in which positive immunostaining to PAP has been observed. The similarity is not well understood, however, as all evidence points to the origin of SC from germ cells in mature cystic teratomas without any embryologic relationship to the hindgut.