Cervical tissue shrinkage by formaldehyde fixation, paraffin wax embedding, section cutting and mounting

Abstract

To evaluate the efficacy of cryocoagulation as a treatment for cervical intraepithelial neoplasia (C.I.N.), it is necessary to know the maximum depth of the glandular crypts, the maximum crypt involvement by C.I.N. and the extension of the cryolesion, obtained under standardized conditions. In a morphometric study on this subject, one has to take into account the shrinkage of the cervical tissue, caused by processing the tissue for histological examination. In the present study, tissue shrinkage of the cervix in different directions was measured in three separate steps. First shrinkage caused by formalin fixation was determined, second shrinkage caused by dehydration, clearing and paraffin wax embedding and finally that caused by section cutting and mounting. Shrinkage caused by formalin fixation, and by dehydration, clearing and paraffin wax embedding did not differ significantly in the different directions and resulted in an average shrinkage of respectively 2.7% and 12.6% of the original dimensions. The alterations of the dimensions by section cutting and mounting is not a process of shrinkage, but actually a deformation caused by pressure on the tissue during sectioning. Generally the dimension decreases in the cutting direction and increases in the direction perpendicular to it. In the calculation of the total shrinkage these alterations can be neglected, since the changes, although not consistent are small. It follows that in morphometric studies a total shrinkage of about 15% of the original dimensions has to be taken into consideration.

Two distinct events, section compression and loss of particles (“lost caps”), contribute toz-axis distortion and bias in optical disector counting

“…The most likely explanation for z-axis distortion is the physical compression of tissues adjacent to the knife when the knife blade hits the block of tissue (Boonstra et al, 1983). This is thought to result in compression of surface regions of the tissue section more than the core (Figs.…”

Quantification of surgical margin shrinkage in the oral cavity

“…Notably, in Siu's study, the tumor itself only shrank 10%, probably resulting from replacement of the contractile esophageal musculature with non-contractile tumor tissue. In a study of uterine cervical tissue by Boonstra et al, 15 fixation in an 8% formalin solution resulted in a 2.7% shrinkage, whereas dehydration, clearing, and paraffin imbedding produced a 12.6% loss of length. They also found that specimen cutting resulted in a slight increase in the horizontal dimension of the margin (0.4%) and that the deep margin was reduced by 2.2%, intuitively corresponding to the crushing effect of perpendicularly oriented force on the knife blade.…”

Vulvar carcinoma

“…In earlier morphometric studies in the cervix, we found that shrinkage of 15% of the specimen had to be taken into consideration. 34 Based on our current results, we have decided to change the intended surgical margins from 1 cm to 2 cm.…”