Graduate Thesis Or Dissertation
 

Factors Affecting Histologic Tumor Free Margins in Widely Excised Feline Injection Site Sarcomas

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/7s75dg163

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  • Feline injection site sarcomas (FISS) are frequently encountered cutaneous and subcutaneous neoplasms of cats. Significant patient morbidity is related to the invasiveness these tumors display, typically requiring extensive local excision or amputation. As with many veterinary tumors, survival time and tumor recurrence for FISS is highly influenced by histologic margin status. A general reduction between surgical and histologic margins is expected, but the magnitude, timing and potential factors involved remain poorly described in the veterinary literature. In the first study presented, we begin to define the degree and timing of lateral margin shrinkage in widely excised feline injection site sarcoma specimens. Lateral margins were measured around spontaneously occurring FISS at 1) the time of surgery from grossly palpable tumor 2) immediately following excision 3) following formalin fixation from specimen CT scans and 4) histologic margins. Consistent with other reports, our findings indicate that the majority of clinically relevant shrinkage occurs prior to formalin fixation (29% decrease from surgically measured margins, p = 0.005). In total, histologic margins represented only 50% of surgically planned margins (p = 0.0012). In the second report, we showed that FISS tumors themselves do not shrink to the same degree as the normal surrounding tissue. This was done using both standard two dimensional CT scans before and after excision of FISS tumors and three dimensional computed tomography software. Tumor volume was calculated using the ellipsoid formula and compared to volume reported using 3D software. We showed that FISS tumor dimensional shrinkage following formalin fixation was small (<7%) and less than that reported for normal feline tissues. The complexity of FISS peritumoral projections was highlighted and proposed reason why volume calculations using the ellipsoid formula was less than 3D imaging for both in vivo (mean 25.8% smaller, p = 0.038) and ex vivo (mean 24.8% smaller, p = 0.017). Taken together, these data begin to define and further explore the discrepancy between surgical and histologic margins for FISS. It is reasonable to suspect similar margin reductions around other feline cutaneous and subcutaneous neoplasms, making this data more globally applicable. Future investigation on additional factors that affect margin size and interpretation (eg section number, inking protocol) are needed. Ultimately, with a better understanding of the influences on margin reduction, we may be able to have a more evidence based approach to surgical planning and thereby potentially reduce patient morbidity. Similarly, with additional data on the above topics, we may begin to further correlate the magnitude of histologic margin with prognosis and survival time for FISS and other veterinary neoplasms.
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