Within an hour after removal from the body, tissue samples should generally be placed in vessels with the correct fixing solution, with a volume that allows them to lie freely in the solution. The standard fixation fluid is generally 10% neutral buffered formalin, which is roughly equivalent to 4% formaldehyde.
The main exception to using formalin are mainly:
- A tophus or other specimen suspicious for gout versus pseudogout should be sent in alcohol or dry, since formalin will dissolve the crystals.
- Lymph nodes (or other lymphoid aggregates) with a suspicion of lymphoma, where samples are generally put in a special solution for flow cytometry.
- Products of conception with a need to take samples for genetic testing.
- . Breast pathology grossing guidelines. UCLA Health. Retrieved on 2021-09-09.
- Katarzyna Lundmark, Krynitz, Ismini Vassilaki, Lena Mölne, Annika Ternesten Bratel. Handläggning av hudprover – provtagningsanvisningar, utskärningsprinciper och snittning (Handling of skin samples - Instructions for sampling, cutting and incision. KVAST (Swedish Society of Pathology). Retrieved on 2019-09-09.
- . Paraformaldehyde, Formadehyde and Formalin. Duke University. Retrieved on 2019-12-17.