The Use Of Pap To Demonstrate The S100 Antigen In Neoplastic Spleens From Beagle Dogs That Have Been Exposed To Terminated Protracted Whole-Body Gamma Irradiation

Abstract

Thirteen sections of primary splenic sarcomas manifested by eight beagle dogs exposed to protracted ^°Co gamma irradiation were characterized by the use of staining methods. Gomori’s Reticulum stain, Masson’s Trichrorae stain, and PAP (peroxidase-antiperoxidase), an immunohistochemical staining method specific for localization of the S100 antigen, were employed in an attempt to reconcile and unify conflicting histological and ultrastructural evaluations of these tumors. The S100 antigen is thought to be indicative of a neurogenic cytogenealogy. All three staining methods were utilized because of their inclusion in a protocol developed to arrive at a differential diagnosis concerning these primary soft tissue lesions of the spleen. The results obtained with Masson's method, support differential diagnoses which postulate myogenic, as well as fibrosarcomatous origins for these lesions. All sections exhibited reticulum patterns not out of context with those exhibited by normal splenic stromal elements, when stained with Gomori’s method. Therefore, no specific usefulness was seen for the application of Gomori’s method to these neoplasms. The majority of the sections exhibited no 3100 protein antigenicity. The 3100 positivity manifested by three sections was thought to be due to the cells histiocytic, and not neutogenic origin. The relative lack of S100 protein expression within these lesions can be ascribed to one of three explanations: 1) These neoplastic tissues do not contain the S100 antigenic protein; 2) The methods employed to fix and embed the sections are not conducive to preservation of the S100 antigen; or, 5) The relatively undifferentiated state which characterizes these lesions allows for the possibility that the 3100 phenotypic expression is not yet fully developed. Explanations one and three argue against neurogenic conclusions regarding the cytogenealogy of the sections. The second explanation has it’s genesis in poor experimental procedure and threrfore no conclusions about the validity of a neurogenic diagnosis may be drawn if it is accepted. Within this study the lack of endogenous neural positivity in the sections supports premise number two. It is concluded that diagnoses that involve neurogenic origins for these neoplasms (i.e., Schwannoma) remain questionable and the immunological recharacterization of these sections, coupled with more extensive electro* microscopic evaluations being cited as possible means by which final diagnoses may be ultimately made. It is also postulated that the extended exposure to formalin fixations, along with the rigors of paraffin embedding which was endured by the specimens may have denatured the S100 antigen’s integrity to a degree such that it would not allow for it’s recognition by the S100 specific antibody. Therefore the usefulness of immunohistochemical staining techniques (PAP S100) in establishing the differential as well as a final diagnosis is limited by the preparation procedure employed in the fixation and sectioning the specimens.