Histologic differences between cryothermic and hyperthermic therapies

Abstract

Minimally invasive cryothermic and hyperthermic therapies are being increasingly used to destroy dysfunctional and neoplastic tissues in several organ systems. This report morphologically compares the acute tissue responses that follow cryothermic and microwave therapy in porcine kidneys. Three cryothermic and hyperthermic groups of treated kidneys were pooled from other studies for evaluation (six groups; six kidneys/group): 1) in vitro treated non-perfused, 2) in situ treated with 2-hour post in vivo perfusion, and 3) in situ treated with 3-day (cryothermic) or 7-day (hyperthermic) post in vivo perfusion. The cryolesions showed uniform central coagulative-type necrosis and interstitial hemorrhage. The hyperthermic lesions showed central thermal fixation and a rim of coagulative necrosis. The cryothermic and hyperthermic lesions both had a similar narrow transition zone of partial cell injury. The cryothermic lesions developed a wound healing response that advanced into the central lesion. In contrast, the heat-treated tissues lacked a prominent wound healing response and appeared to resist breakdown/repair by the body. Thus, the tissue effects of and responses to cryothermic and heat injury appear to be different.

Monitoring prostate thermal therapy with diffusion‐weighted MRI

“…Compared to the left cyst‐forming lesion, the right lesion was heated with higher power for a shorter period of time. This observation is consistent with a prior report on the body's different response to “heat‐fixed” region and transition zone region in a swine renal model (26).…”

Correlation of contrast-enhanced MR images with the histopathology of minimally invasive thermal and cryoablation cancer treatments in normal dog prostates

“…Microscopic findings in thermally ablated tissues in animals and humans have been described, but many lack mention of subtle cellular changes described in these studies (8,10,(16)(17)(18)(19). In HUS treated prostates, the heated tissue appears "normal" at low power, and is generally surrounded by a more prominently affected zone in which the histoarchitecture is severely disrupted (15,20,21). In the center of the lesions (or those areas subjected to the highest thermal dose), the high temperatures coagulate cellular structural proteins and proteinaceous secretory granules, and the extracellular matrices undergo hyalinization.…”

“…Similar nuclear changes were noted in the interstitial vascular endothelium and smooth muscle cell nuclei. Within the "heat fixed zone" (HFZ) (15), subtle changes consistent with cellular thermal damage/coagulation included the following: loss of cytoplasmic "granularity" typical of normal canine prostatic epithelium, thin, elongated nuclei in slightly elongated epithelial cells, minimal, discontinuous separations between epithelial cells and basement membranes, minimal pyknotic debris, and mild interstitial edema. A total lack of TTC staining on fresh prostate slices correlated with these heat-fixed regions.…”

“…Most glands were devoid of any attached epithelial lining cells and had lumina filled with sloughed epithelial cells and granular eosinophilic debris ( Figure 6C). We referred to these areas as the fragmented or transition zone (TZ) (15). The interstitial connective tissue in these regions contained congested capillaries and small venules, and collagen fibers separated by clear spaces, consistent with acute interstitial edema.…”

Thermal Injury Prediction During Cryoplasty Through In Vitro Characterization of Smooth Muscle Cell Biophysics and Viability

“…31 Other advantages of freezing include maintenance of ECM structure, 33 the minimally invasive approach and lack of coagulation effects, i.e., thermal fixation. 12 Recently, a thermal model analyzing the temperature distribution in arteries during cryoplasty was reported. 38 Though relevant, assumption of constant thermal properties for tissues during freezing will affect predicted temperatures and cooling rates.…”