Histopathological findings in colorectal liver metastases after electrochemotherapy.

Electrochemotherapy of colorectal liver metastases has been proven to be feasible, safe and effective in a phase I/II study. In that study, a specific group of patients underwent two-stage operation, and the detailed histopathological evaluation of the resected tumors is presented here. Regressive changes in electrochemotherapy-treated liver metastases were evaluated after the second operation (in 8-10 weeks) in 7 patients and 13 metastases when the treated metastases were resected. Macroscopic and microscopic changes were analyzed. Electrochemotherapy induced coagulation necrosis in the treated area encompassing both tumor and a narrow band of normal tissue. The area became necrotic, encapsulated in a fibrous envelope while preserving the functionality of most of the vessels larger than 5 mm in diameter and a large proportion of biliary structures, but the smaller blood vessels displayed various levels of damage. At the time of observation, 8-10 weeks after electrochemotherapy, regenerative changes were already seen in the peripheral parts of the treated area. This study demonstrates regressive changes in the whole electrochemotherapy-treated area of the liver. Further evidence of disruption of vessels less than 5 mm in diameter and preservation of the larger vessels by electrochemotherapy is provided. These findings are important because electrochemotherapy has been indicated for the therapy of metastases near major blood vessels in the liver to provide a safe approach with good antitumor efficacy

Focus of residual vital carcinoma.

<p>Almost completely necrotic tumor tissue (black arrow head). The only focus of the residual vital tumor infiltration is present in the pseudocapsule at the border of ablated area and liver parenchyma (black arrow). H&E, 20x.</p

Gross appearance of electrochemotherapy-treated colorectal liver metastasis.

<p>The treated area was greenish-yellow. Black arrow indicates the pseudocapsule. Red arrow shows clear lumen of the larger vascular structures.</p

Changes in the vicinity of larger veins.

<p>A: Regressive changes extending up to the wall of a large vein without the presence of vital tumor tissue between the vessel wall and area of regressive changes. Lumina of the vein (black arrow head); vessel wall (red arrow head). Area occupied by regressive changes (blue arrow head) with chronic inflammatory cells (green arrow), proliferating small bile ducts (black arrow) and erythrocyte extravasates (red arrow). H&E, 5x. B: Small, peripheral recanalized thrombus (green arrow head) in the same vein located at the very border of the ablated area. Recanalization (purple arrow); venous wall (red arrow head) and lumina (black arrow head). Peripheral portion of the regressive changes is shown in detail in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0180709#pone.0180709.g005" target="_blank">Fig 5A</a> (blue arrow head). H&E, 5x.</p

Area of the electrode insertion.

<p>A: Tissue areas with necrosis and ingrowth of granulation tissue (black arrow head). H&E 10x. B: Vicinity of the insertional area: complete necrosis of the portal tract (red arrow head) with leakage of bile (black arrow). In the lower right part ingrowth of granulation tissue can be seen (blue arrow head). H&E, 10x.</p

Ablated area.

<p>A: Peripheral part of the ablated area with ingrowth of granulation tissue (green arrow head), necrosis (black arrow head), and pseudocapsule (red arrow head). H&E, 10x. B: Coagulation necrosis of the liver parenchyma (blue arrow head), metastatic tumor tissue (black arrow head) and pseudocapsule (red arrow head). H&E, 5x. C: Coagulation necrosis of the liver parenchyma (blue arrow head) with portal tracts (black arrows) and necrotic tumor tissue (black arrow head). H&E, 5x.</p

Damage to the liver structures.

<p>A: Larger portal tract showing different degrees of damage in the orthotopic structures; biliary duct with intact wall and undamaged epithelium (black arrows). Only some erythrocyte extravasates are present in the walls (red arrow). In the middle and left part of the image, a few blood vessels with various degrees of damage are shown–the branch of the hepatic artery (black arrow head) showing preserved scaffold and the branch of the portal vein showing complete thrombosis (blue arrow head). H&E, 5x. B: Damaged vessel showing preserved structure but without viable cells (preserved scaffold) (black arrow). H&E, 20x. C and D: Different levels of damage in the same blood vessel–on the left portion, there are no viable cells on the vessel wall (black arrows), and only connective tissue structures are present, while the right portion still shows viable cells in the endothelium and tunica media (red arrows). C: H&E 10x; D: H&E, 20x. E: Blood vessel at the periphery of ablated area with recanalized thrombus (black arrow head). Wall of the vessel (blue arrow head). H&E, 20x.</p

Boundary of the ablated tissue and liver parenchyma.

<p>A and B: pseudocapsule (blue arrow heads); necrosis in the ablated area (red arrow heads); viable liver parenchyma outside the treated area (black arrow heads). A: H&E 5x. B: H&E 10x. C: Boundary of the treated hepatic parenchyma and pseudocapsule: some chronic inflammatory infiltrates consisting of lymphocytes (green arrows), plasma cells (yellow arrows), focal siderophages (blue arrows) and proliferating small bile ducts (black arrows) and multinucleated hepatocytes (red arrows). H&E 20x.</p