Acid formalin haematin pigment is associated with which fixative?

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!

Acidic conditions during fixation drive pigment formation. When tissue is fixed in unbuffered formalin, the solution is acidic and hemoglobin in blood-rich areas can decompose to hematin, producing acid formalin hematin pigment. This brown to black granular pigment is an artifact that commonly appears along vessels and in areas with red cells, and it persists through standard processing. Using neutral buffered formalin keeps the pH near neutral, preventing the formation of acid hematin and thus minimizing this pigment. Therefore, acid formalin hematin pigment is associated with unbuffered formalin fixative.