Changes in the dimension and volume of feline injection-site sarcomas following formalin fixation as determined by use of the ellipsoid volume formula and three-dimensional computed tomography software

Abstract

OBJECTIVE To evaluate changes in the dimension and volume of feline injection-site sarcomas (FISSs) before (in vivo) and after surgical excision and formalin fixation (ex vivo) as determined by measurements obtained from 2-D and 3-D CT images. SAMPLE 10 excised FISSs. PROCEDURES The maximum length, width, and depth of each FISS were measured on contrast-enhanced 2-D CT images of the tumor obtained in vivo and ex vivo. Those measurements were used to estimate tumor volume with the standard ellipsoid formula. Tumor volume was also calculated from 3-D CT images with software that used a volume-rendering algorithm. Student paired t tests were used for comparisons between the in vivo and ex vivo assessments. RESULTS Small decreases were detected in maximum tumor length, width, and depth between the in vivo and ex vivo assessments; however, tumor length was the only dimension that decreased significantly between the 2 assessments. Median tumor volume decreased significantly between the in vivo and ex vivo assessments regardless of the method used to estimate it. Tumor volume estimated by the ellipsoid formula was significantly lower than that estimated by the 3-D CT software at both assessments. CONCLUSIONS AND CLINICAL RELEVANCE Results indicated that shrinkage of FISSs following excision and formalin fixation was small and may be less than that of grossly normal tissue. Tumor volume estimated by the ellipsoid formula was consistently less than that estimated by 3-D CT software and should not be used when accuracy of tumor volume is of particular concern and advanced CT imaging is available.

Reductions in margin length after excision of grade II mast cell tumors and grade I and II soft tissue sarcomas in dogs

“…A previous study on normal canine skin reported that samples increased in thickness by 45%‐76% following formalin fixation . These findings are partially compatible with a prior study, where CT‐dimensions of feline injection site sarcoma were reduced due to formalin fixation, but only in terms of tumor length …”

“…12 These findings are partially compatible with a prior study, where CTdimensions of feline injection site sarcoma were reduced due to formalin fixation, but only in terms of tumor length. 29 One of the primary limitations in the present report is the lack of high-grade tumors in the study population. Changes in the reactive zone of the tumor, including microscopic infiltration with neoplastic cells, could be more pronounced with high-grade MCT and/or STS.…”

“…When STS margin length reductions at each processing step were compared, all were significantly different from each other (P < .0001) except for ex vivo vs postfixation GNSM and SNSM vs HTFM (Figure 3). The maximum circumferential surgical margin length reduction (from in vivo GNSM through HTFM) was 29 . Deep margin length reductions from SNSM to HTFM were a median (IQR) of 1.0 mm (0.3-3.1 mm) and 0.5 mm (-0.2 to 2.0 mm) for MCT and STS, respectively.…”

Dynamic tomographic studies of interscapular feline injection-site sarcoma: essential or useless practice?

“…8,10 There are few published studies concerning new imaging strategies for specifically defining the anatomy of the region, 11 and consequently its margins, or for computing the real volume of the neoplasm, which increase the agreement with histopathological measurements. 10,12 Moreover, the effects of formalin fixation on the assessment of tumour volume were investigated by comparing CT measurements with histopathology. 12 The results showed slight shrinkage of the FISS after excision and formalin fixation.…”

“…10,12 Moreover, the effects of formalin fixation on the assessment of tumour volume were investigated by comparing CT measurements with histopathology. 12 The results showed slight shrinkage of the FISS after excision and formalin fixation. The tumour volume estimated by three-dimensional (3D) software was described to be more accurate than the results of the ellipsoid formula, suggesting that the former method should be used when accurate estimation of tumour volume is particularly challenging on CT. 12 In 2013, it was postulated that as a consequence of the high mobility of the interscapular region, a common location for FISS, 2 the relationship between the mass and the surrounding tissues may change depending on the position of the forelimbs during the CT examination.…”