Acid formalin haematin pigment cannot be prevented by routine washes; which approach can prevent it?

Study for the CAMLPR Histology Practice Test. Study with flashcards and multiple choice questions, each question has hints and explanations. Get ready for your exam!

Acid formalin hematin pigment is an artifact that forms when formalin-fixed tissue is exposed to acidic conditions, producing a dark, insoluble pigment that can mimic melanin. The most effective way to prevent this is to remove any existing pigment and keep the tissue in an environment that discourages new pigment formation before staining. An alcoholic picric acid wash helps solubilize and remove acid hematin, while following with an alkaline alcohol wash (often with a touch of acetic acid to stabilize the pH) keeps the tissue conditions alkaline and prevents re-formation of the pigment. Water washes or simple buffer washes don’t sufficiently remove or counteract the acidic conditions that promote pigment formation, and saying that no prevention is possible is inaccurate because this dual-step approach is a standard preventive measure.