Formalin Versus Bouin Solution for Rat Testicular Tissue Fixation: A Histochemical and Immunohistochemical Evaluation

Background: An accurate histopathological assessment and reporting of testicular biopsies require an appropriate tissue fixative. We assessed the histological, histochemical, and immunohistochemical quality of testicular biopsies, comparing 10% formalin versus Bouin solution as tissue fixatives. Methods: This experimental study utilized 20 adult male albino rats equally divided into five cages for 30 days. By the end of the experiment, all animals were anesthetized, and both testes were removed and weighted; one testicle was fixed in 10% formalin and the other testicle in Bouin solution, offering 40 specimens and then subjected to histological, morphometric, histochemical, and immunohistochemical assessments. Results: Formalin revealed high-quality cytological details and better nuclear chromatin detail (P=0.03). At the architectural level, the Bouin solution showed better quality details with less cytoplasmic shrinkage of seminiferous tubule germ cells (P=0.001). Bouin’s fixed tissues were more suitable for staining by trichrome methods but unsuitable when subsequent immunohistochemistry was requested. The diagnostic concordance between the Bouin solution versus formalin-fixed biopsies was 91.7%. Conclusion: This study supports that the morphology of testicular tissue fixed with Bouin solution was nearly comparable to those fixed with 10% neutral buffered formalin. However, the Bouin solution cannot substitute formalin when subsequent immunohistochemistry is considered.