Orth solution is the best fixative for pheochromocytomas when IHC is not to be performed.

• A. True
• B. False
• C. Depends on the case
• D. Not used

Answer: (A)

Fixation choice can influence whether catecholamine-containing chromaffin granules in pheochromocytoma are preserved well enough to be demonstrated histochemically when immunohistochemistry is not used. Orth solution contains chromium-based components that stabilize these granules and allow the chromaffin reaction to occur reliably in tissue sections. When immunohistochemistry isn’t planned, this histochemical confirmation is a useful way to support a pheochromocytoma diagnosis, and Orth solution is particularly suited for preserving the chromaffin material needed for that demonstration. Formalin cross-linking, by contrast, can diminish the chromaffin reaction, making histochemical confirmation less dependable. Therefore, using Orth solution is the best fixative in this scenario.