Variability of tissue mechanical response in Sus Domesticus porcine models from in vivo to ex vivo conditions.

BACKGROUND: Healthcare simulators have been demonstrated to be a valuable resource for training several technical and nontechnical skills. A gap in the fidelity of tissues has been acknowledged as a barrier to application for current simulators; especially for interventional procedures. Inaccurate or unrealistic mechanical response of a simulated tissue to a given surgical tool motion may result in negative training transfer and/or prevents the "suspension of disbelief" necessary for a trainee to engage in the activity. Thus, where it is relevant to training outcomes, there should be an effort to create healthcare simulators with simulated tissue mechanical responses that match or represent those of biological tissues. Historically, this data is most often gathered from preserved (post mortem) tissue; however, there is a concern that the mechanical properties of preserved tissue, that lacks blood flow, may lack adequate accuracy to provide the necessary training efficacy of simulators. METHODS AND FINDINGS: This work explores the effect of the "state" of the tissue testing status on liver and peritoneal tissue by using a customized handheld grasper to measure the mechanical responses of representative porcine (Sus domesticus) tissues in n = 5 animals across five test conditions: in vivo, post mortem (in-situ), ex vivo (immediately removed from fresh porcine cadaver), post-refrigeration, and post-freeze-thaw cycle spanning up to 72 hours after death. No statistically significant difference was observed in the mechanical responses due to grasping between in vivo and post-freeze conditions for porcine liver and peritoneum tissue samples (p = 0.05 for derived stiffness at grasping force values F = 5N and 6.5N). Furthermore, variance between in vivo and post-freeze conditions within each animal, was comparable to the variance of the in vivo condition between animals. CONCLUSIONS: Results of this study further validate the use of preserved tissue in the design of medical simulators via observing tissue mechanical responses of post-freeze tissue comparable to in vivo tissue. Therefore, the use of thawed preserved tissue for the further study and emulation of mechanical perturbation of the liver and peritoneum can be considered. Further work in this area should investigate these trends further, particularly in regard to other tissues and the potential effects varying preservation methods may yield.

Epithelioid myofibroblastoma with concurrent presentation of LCIS and DCIS.

Myofibroblastoma (MFB) of the breast is a rare benign neoplasm of the mammary stroma. Several morphologic variants have been described in the literature, which can create diagnostic challenges for pathologists, in particular the epithelioid variant of MFB, which can mimic invasive lobular carcinoma. We report a case of a 72-year-old female who presented for a painless breast lump and was later found to have 2 lesions on imaging, with 1 lesion corresponding to the palpable lump and the other lying in a different quadrant. Core-needle biopsies demonstrated ductal carcinoma in-situ at both lesional sites with what was originally felt to be an invasive lobular carcinoma at the lesional site which did not correspond to the palpable lump. After mastectomy, with more complete visualization microscopically of the lesional area originally felt to be an invasive lobular carcinoma, the final pathology was consistent with a MFB, predominantly epithelioid variant, in addition to ductal carcinoma in-situ and lobular carcinoma in-situ. In this paper we describe the imaging findings of an epithelioid MFB and how its nonspecific nature necessitates close communication between the radiologist and pathologist to make the correct diagnosis.