Computed tomography characteristics of fibrosarcoma — a histological subtype of feline injection-site sarcoma

Abstract

Feline injection-site sarcoma (FISS) may be a consequence of subcutaneous injection. In the present study, the medical records and the computed tomography (CT) features of 22 cats with a FISS, histopathological subtype fibrosarcoma, were used. The majority of the fibrosarcomas (45%) were located in the interscapular region. All fibrosarcomas, except one with mild enhancement, showed strong contrast uptake, characterised as ring (42%), heterogeneous (36%), homogeneous (9%), heterogeneous/ring (6.5%) or mixed heterogeneous/homogeneous enhancement (6.5%). The longest axis of the mass was in a cranio-caudal (68%) or dorso-ventral (32%) direction. The median volume calculated on CT was 7.57 cm(3). Common features were a marked local invasiveness of the musculature and heterogeneity of the tissue in the periphery of the neoplasia. When the fibrosarcoma was interscapular, performing an additional post-contrast scan with the forelimbs positioned caudally along the body, in addition to the standard protocol with the forelimbs extended cranially, allowed better evaluation of the actual relationship between the tumour and the surrounding tissues. The mean number of muscles involved with the tumour was 2.09 with extended and 1.95 with flexed forelimbs. When a lower number of structures was considered infiltrated through the double positioning, a less invasive surgical approach to underlying muscles and scapula was performed.

Feline injection site sarcoma: computed-tomographic density and assessment of tumor dimensions by different methods

“…Largest discrepancies documented in CC axis measurements between methods may have reflected the inclusion of digitiform projections in tomographic estimates of tumor size, easily recognized on CT scans but not on physical examination. Results of the current study support recent CT data (Travetti et al 2013) suggesting that FISS masses have longer CC and DV axes, in this order. Better understanding of FISS growth patterns and behavior is required to clarify the significance of these findings.…”

“…Three-dimensional CT measurement of neoplastic lesions, particularly those with ill-defined margins, may be challenging (Travetti et al 2013). Contrast enhancement is recommended for accurate tumor margin demarcation (Samii 2007) and proved helpful for tumor size determination in this study.…”

“…As in canine mast cell tumors , CT was a more accurate method of measurement than physical examination in this study, particularly in cases where neoplasms projected into surrounding tissues. Moreover, CT recognition of blurring of fat planes, that may represent highly inflamed and vascularized peritumoral tissues or neoplastic infiltration of the panniculus (Webb 2000), that are seldom detected on physical examination plays an important role in effective surgical planning (Travetti et al 2013). Tumors in this study appeared larger on CT than physical examination, particularly when measurements were taken from post-contrast MPR CT images.…”

“…Comparative studies of FISS volume based on CT images and clinical findings (McEntee & Samii 2000, McEntee & Page 2001, Carneiro 2006, Di Giancamillo et al 2011, Carneiro 2012, Travetti et al 2013, Zardo et al 2013) have failed to reach a consensus. While CT yielded larger mean tumor volume estimates than physical examination in most articles, (McEntee & Samii 2000, McEntee & Page 2001, Carneiro 2006, Zardo et al 2013) no significant differences were reported in others (Di Giancamillo et al 2011, Carneiro 2012.…”

“…However, despite several research efforts over the last decades, the etiology of FISS remains undetermined (Woodward 2011, Sparkes 2013. Feline injection site sarcomas tend to form digitiform projections that invade deeper muscular planes (Samii 2007, Martano et al 2011, Carneiro 2012, Travetti et al 2013 and are seldom recognized on physical examination; these projections prevent clear definition of surgical margins and adequate demarcation of radiotherapy fields (VAFSTF 2005). The highly invasive nature of even small-sized FISSs calls for multidisciplinary diagnostic approaches.…”