Influence of formalin fixation on tissue dimensions in palatal tonsils.

AIM: To investigate the change of tissue dimensions after formalin fixation, and to determine the optimal time of fixation.

HYPOTHESIS: Formalin fixation may lead to shrinkage in tissue dimensions and may thus alter tumor stages.

BACKGROUND

It is often observed in tumor surgery that the dimensions in vivo seem larger than after resection, and tissue appears to shrink further after formalin fixation. This might alter dimensions and assessment of spread of the tumor and thus lead to a lesser tumor classification and stage. In cases where the decision for adjuvant chemoradiation is based upon the stage, it may thus be of relevance for the patient to evaluate the pathologic and not the in vivo dimensions of the tumor.

MATERIAL AND

METHODS

In order to obtain comparable tissues, we investigated 100 palatal tonsils after cold steel dissection tonsillectomy for chronic tonsillitis. There were four time points investigated: directly after excision in the operating room and after four, 24 and 72 h of fixation in formaldehyde (4% Formaldehyde in phosphate buffer pH 7.4). The tissue was measured in the following dimensions: volume (ml), weight (g) and length, broadness and width (mm).

RESULTS

The tissue size did not change significantly in dimensions except for an increase in length. The time of fixation did not influence the size.

DISCUSSION: Formalin fixation does not significantly influence the tissue dimensions of palatal tonsils in comparison to direct ex vivo measurements. A minimal time of fixation of 20 h is required in order to stop all degenerative processes; however, longer fixation does not change the dimensions of the specimen.

CONCLUSION

The null hypothesis has to be withdrawn that tissue dimensions are altered by formalin fixation. Thus, the histopathological measurements do not influence TNM staging.