Composition of formalin fixative

1.6. For buffering formalin fixative, a neutral buffered solution should preferably be used; avoid acidic or unbuffered solutions (C).

1.7. A 10% solution (3.7% formaldehyde) should preferably be used as a formalin fixative (C).

Optimal fixation time

1.8. Following the recommendations in several CDx guidelines (Table 3), tissue specimens (surgically or endoscopically resected specimens and biopsy specimens) should be fixed for 6−48 h (C) (Figures 3 and 4 and 6 ).

1.9. Sample quality deteriorates due to inadequate fixation; therefore, insufficient fixation and over fixation should be avoided (N).

Optimal volume of fixative for formalin fixation

1.10.Ten times the sample volume per tissue should be used for formalin fixation (C).

1.11.Formalin fixation can be performed at room temperature (C).