An idiosyncratic zonated stroma encapsulates desmoplastic liver metastases and originates from injured liver.

A perimetastatic capsule is a strong positive prognostic factor in liver metastases, but its origin remains unclear. Here, we systematically quantify the capsule's extent and cellular composition in 263 patients with colorectal cancer liver metastases to investigate its clinical significance and origin. We show that survival improves proportionally with increasing encapsulation and decreasing tumor-hepatocyte contact. Immunostaining reveals the gradual zonation of the capsule, transitioning from benign-like NGFRhigh stroma at the liver edge to FAPhigh stroma towards the tumor. Encapsulation correlates with decreased tumor viability and preoperative chemotherapy. In mice, chemotherapy and tumor cell ablation induce capsule formation. Our results suggest that encapsulation develops where tumor invasion into the liver plates stalls, representing a reparative process rather than tumor-induced desmoplasia. We propose a model of metastases growth, where the efficient tumor colonization of the liver parenchyma and a reparative liver injury reaction are opposing determinants of metastasis aggressiveness.

Generation of vessel co-option lung metastases mouse models for single-cell isolation of metastases-derived cells and endothelial cells.

Tumor vessel co-option, a process in which cancer cells "hijack" pre-existing blood vessels to grow and invade healthy tissue, is poorly understood but is a proposed resistance mechanism against anti-angiogenic therapy (AAT). Here, we describe protocols for establishing murine renal (RENCA) and breast (4T1) cancer lung vessel co-option metastases models. Moreover, we outline a reproducible protocol for single-cell isolation from murine lung metastases using magnetic-activated cell sorting as well as immunohistochemical stainings to distinguish vessel co-option from angiogenesis. For complete details on the use and execution of this protocol, please refer to Teuwen et al. (2021).

The relationship between primary colorectal cancer histology and the histopathological growth patterns of corresponding liver metastases.

BACKGROUND: The histopathological growth patterns (HGPs) are a prognostic and predictive biomarker in colorectal cancer liver metastasis (CRLM). This study evaluates the relationship between the HGP and primary colorectal cancer (CRC) histopathology. METHODS: A total of 183 treatment-naive patients with resected CRC and CRLM were included. Thirteen CRC histopathology markers were determined and compared between the desmoplastic and non-desmoplastic HGP; tumour sidedness, pT&pN stage, tumour grade, tumour deposits, perineural- (lympho-)vascular- and extramural venous invasion, peritumoural budding, stroma type, CRC growth pattern, Crohn's-like lymphoid reaction, and tumour-infiltrating lymphocyte (TIL) density. Logistic regression analysis was performed using both CRC and CRLM characteristics. RESULTS: Unfavourable CRC histopathology was more frequent in non-desmoplastic CRLM for all markers evaluated, and significantly so for a lower TIL density, absent Crohn's-like lymphoid reaction, and a "non-mature" stroma (all p < 0.03). The cumulative prevalence of unfavourable CRC histopathology was significantly higher in patients with non-desmoplastic compared to desmoplastic CRLM, with a median (IQR) of 4 (3-6) vs 2 (1-3.5) unfavourable characteristics observed, respectively (p < 0.001). Multivariable regression with 9 CRC histopathology markers and 2 CRLM characteristics achieved good discriminatory performance (AUC = 0.83). CONCLUSIONS: The results of this study associates primary CRC histopathology with the HGP of corresponding liver metastases.

Histopathological growth patterns of liver metastasis: updated consensus guidelines for pattern scoring, perspectives and recent mechanistic insights.

The first consensus guidelines for scoring the histopathological growth patterns (HGPs) of liver metastases were established in 2017. Since then, numerous studies have applied these guidelines, have further substantiated the potential clinical value of the HGPs in patients with liver metastases from various tumour types and are starting to shed light on the biology of the distinct HGPs. In the present guidelines, we give an overview of these studies, discuss novel strategies for predicting the HGPs of liver metastases, such as deep-learning algorithms for whole-slide histopathology images and medical imaging, and highlight liver metastasis animal models that exhibit features of the different HGPs. Based on a pooled analysis of large cohorts of patients with liver-metastatic colorectal cancer, we propose a new cut-off to categorise patients according to the HGPs. An up-to-date standard method for HGP assessment within liver metastases is also presented with the aim of incorporating HGPs into the decision-making processes surrounding the treatment of patients with liver-metastatic cancer. Finally, we propose hypotheses on the cellular and molecular mechanisms that drive the biology of the different HGPs, opening some exciting preclinical and clinical research perspectives.

Predicting 10-year survival after resection of colorectal liver metastases; an international study including biomarkers and perioperative treatment.

BACKGROUND: The aim of this study was to develop a prediction model for 10-year overall survival (OS) after resection of colorectal liver metastasis (CRLM) based on patient, tumour and treatment characteristics. METHODS: Consecutive patients after complete resection of CRLM were included from two centres (1992-2019). A prediction model providing 10-year OS probabilities was developed using Cox regression analysis, including KRAS, BRAF and histopathological growth patterns. Discrimination and calibration were assessed using cross-validation. A web-based calculator was built to predict individual 10-year OS probabilities. RESULTS: A total of 4112 patients were included. The estimated 10-year OS was 30% (95% CI 29-32). Fifteen patient, tumour and treatment characteristics were independent prognostic factors for 10-year OS; age, gender, location and nodal status of the primary tumour, disease-free interval, number and diameter of CRLM, preoperative CEA, resection margin, extrahepatic disease, KRAS and BRAF mutation status, histopathological growth patterns, perioperative systemic chemotherapy and hepatic arterial infusion pump chemotherapy. The discrimination at 10-years was 0.73 for both centres. A simplified risk score identified four risk groups with a 10-year OS of 57%, 38%, 24%, and 12%. CONCLUSIONS: Ten-year OS after resection of CRLM is best predicted with a model including 15 patient, tumour, and treatment characteristics. The web-based calculator can be used to inform patients. This model serves as a benchmark to determine the prognostic value of novel biomarkers.

Suppression of Endothelial Cell FAK Expression Reduces Pancreatic Ductal Adenocarcinoma Metastasis after Gemcitabine Treatment.

Despite substantial advances in the treatment of solid cancers, resistance to therapy remains a major obstacle to prolonged progression-free survival. Pancreatic ductal adenocarcinoma (PDAC) is one of the most aggressive cancers, with a high level of liver metastasis. Primary PDAC is highly hypoxic, and metastases are resistant to first-line treatment, including gemcitabine. Recent studies have indicated that endothelial cell (EC) focal adhesion kinase (FAK) regulates DNA-damaging therapy-induced angiocrine factors and chemosensitivity in primary tumor models. Here, we show that inducible loss of EC-FAK in both orthotopic and spontaneous mouse models of PDAC is not sufficient to affect primary tumor growth but reduces liver and lung metastasis load and improves survival rates in gemcitabine-treated, but not untreated, mice. EC-FAK loss did not affect primary tumor angiogenesis, tumor blood vessel leakage, or early events in metastasis, including the numbers of circulating tumor cells, tumor cell homing, or metastatic seeding. Phosphoproteomics analysis showed a downregulation of the MAPK, RAF, and PAK signaling pathways in gemcitabine-treated FAK-depleted ECs compared with gemcitabine-treated wild-type ECs. Moreover, low levels of EC-FAK correlated with increased survival and reduced relapse in gemcitabine-treated patients with PDAC, supporting the clinical relevance of these findings. Altogether, we have identified a new role of EC-FAK in regulating PDAC metastasis upon gemcitabine treatment that impacts outcome. SIGNIFICANCE: These findings establish the potential utility of combinatorial endothelial cell FAK targeting together with gemcitabine in future clinical applications to control metastasis in patients with pancreatic ductal adenocarcinoma.

Local tumour control after radiofrequency or microwave ablation for colorectal liver metastases in relation to histopathological growth patterns.

BACKGROUND: Regrowth after ablation is common, but predictive factors for local control are scarce. This study investigates whether histopathological growth patterns (HGP) can be used as a predictive biomarker for local control after ablation of colorectal liver metastases (CRLM). METHODS: Patients who received simultaneous resection and ablation as first treatment for CRLM between 2000 and 2019 were considered eligible. HGPs were determined on resected CRLM according to international guidelines and were classified as desmoplastic or non-desmoplastic. As minimal inter-tumoural heterogeneity has been demonstrated, the HGP of resected and ablated CRLM were presumed to be identical. Local tumour progression (LTP) was assessed on postoperative surveillance imaging. Uni- and multivariable competing risk methods were used to compare LTP. RESULTS: In total 221 patients with 443 ablated tumours were analysed. A desmoplastic HGP was found in 60 (27.1%) patients who had a total of 159 (34.7%) ablated lesions. Five-year LTP [95%CI] was significantly higher for ablated CRLM with a presumed non-desmoplastic HGP (37% [30-43] vs 24% [17-32], Gray's-test p = 0.014). On multivariable analysis, a non-desmoplastic HGP (adjusted HR [95%CI]; 1.55 [1.03-2.35]) was independently associated with higher LTP rates after ablation. CONCLUSION: HGP is an independent predictor of local tumour progression following ablation of CRLM.

Histopathological growth patterns of resected non-colorectal, non-neuroendocrine liver metastases: a retrospective multicenter study.

BACKGROUND: Distinct Histopathological Growth Patterns can be identified in liver metastases from melanoma, breast and colorectal cancers. For each of these distinct liver metastasis types the HGP has proven a biomarker for survival after partial hepatectomy, with the desmoplastic type marking favourable prognosis. Whether HGPs can be considered a pan-cancer phenomenon remains unknown. This study therefore evaluates the presence of HGPs and their prognostic value across non-colorectal non-neuroendocrine liver metastases. METHODS: A retrospective multicentre cohort study was performed in patients who underwent curative intent resection of non-colorectal non-neuroendocrine liver metastasis. HGPs were assessed on Haematoxylin and Eosin slides according to consensus guidelines and classified as desmoplastic or non-desmoplastic. Overall- and recurrence-free survival were evaluated using Kaplan-Meier and multivariable Cox regression analysis. RESULTS: In total, 132 patients with liver metastasis from 25 different tumour types were eligible for analysis, of which 26 (20%) had a desmoplastic HGP. Five-year OS and RFS (95%CI) were 53% (36-78%) versus 40% (30-53%), and 33% (19-61%) versus 15% (9-27%) for patients with desmoplastic compared to non-desmoplastic metastases, respectively (p = 0.031 & p = 0.004). On multivariable analysis (adjusted HR [95%CI]) a desmoplastic HGP was prognostic for both OS (0.46 [0.25-0.86]) and RFS (0.38 [0.21-0.69]). CONCLUSIONS: This study demonstrates that HGPs apply to liver metastases across a wide variety of primary tumour origins. They hold a prognostic value in these cases, suggesting that HGPs could represent a pan-cancer biomarker for survival after surgical resection of liver metastases.

Coagulation/fibrinolysis and circulating tumor cells in patients with advanced breast cancer.

PURPOSE: To evaluate the relationship between circulating tumor cells (CTCs) and standard coagulation tests in both a discovery and a validation cohort of patients with advanced breast cancer. METHODS: In a retrospective (n = 77) and a prospective (n = 92) study of patients with progressive advanced breast cancer, CTC count, platelet number, fibrinogen level, D-dimers, prothrombin time, and activated partial thromboplastin time were measured. The association between these coagulation studies and CTC count was analyzed. The impact of these measurements on overall survival (OS) was assessed. RESULTS: In both cohorts, results were similar; absolute CTC count was significantly associated to D-dimer level and inversely with platelet count. In the prospective cohort, quantification of tumor-derived extracellular vesicles (tdEVs) was associated with CTC count, and with coagulation abnormalities (low platelet count and increased D-dimers). tdEVs did not add to CTC count in predicting changes in platelets or D-dimers. In multivariate analysis only CTC ≥ 5 CTC/7.5 mL, ER status, HER2 status and lines of chemotherapy were associated with OS. In patients with terminally metastatic breast cancer, very high CTC counts are prevalent. CONCLUSION: A significant association exists between increasing CTC number and increased D-dimers and decreased platelet counts, suggesting a potential role for CTCs as a direct contributor of intravascular coagulation activation. In patients with advanced and progressive breast cancer, abnormalities in routine coagulation tests is the rule. In patients with terminally advanced breast cancer a "leukemic" phase with high CTC count is prevalent.

Vessel co-option and angiotropic extravascular migratory metastasis: a continuum of tumour growth and spread?

Two fields of cancer research have emerged dealing with the biology of tumour cells localised to the abluminal vascular surface: vessel co-option (VCo), a non-angiogenic mode of tumour growth and angiotropic extravascular migratory metastasis (EVMM), a non-hematogenous mode of tumour migration and metastasis. VCo is a mechanism by which tumour cells gain access to a blood supply by spreading along existing blood vessels in order to grow locally. Angiotropic EVMM involves "pericytic mimicry" (PM), which is characterised by tumour cells continuously migrating in the place of pericytes distantly along abluminal vascular surfaces. When cancer cells are engaged in PM and EVMM, they migrate along blood vessels beyond the advancing front of the tumour to secondary sites with the formation of regional and distant metastases. In the present perspective, the authors review the current scientific literature, emphasising the analogies between embryogenesis and cancer progression, the re-activation of embryonic signals by "cancer stem cells", and the important role of laminins and epithelial-mesenchymal-transition. This perspective maintains that VCo and angiotropic EVMM constitute complementary processes and represent a continuum of cancer progression from the primary tumour to metastases and of tumour growth to EVMM, analogous to the embryonic development program.

Histopathological growth patterns modify the prognostic impact of microvascular invasion in non-cirrhotic hepatocellular carcinoma.

BACKGROUND: Microvascular invasion (MVI) is an established prognosticator in hepatocellular carcinoma (HCC). Histopathological growth patterns (HGPs) classify the invasive margin of hepatic tumors, with superior survival observed for the desmoplastic HGP. Our aim was to investigate non-cirrhotic HCC in light of MVI and the HGP. METHODS: A retrospective cohort study was performed in resected non-cirrhotic HCC. MVI was assessed prospectively. The HGP was determined retrospectively, blinded, and according to guidelines. Overall and disease-free survival (OS, DFS) were evaluated by Kaplan-Meier and multivariable Cox regression. RESULTS: The HGP was determined in 155 eligible patients, 55 (35%) featured a desmoplastic HGP. MVI was observed in 92 (59%) and was uncorrelated with HGP (64% vs 57%, p = 0.42). On multivariable analysis, non-desmoplastic and MVI-positive were associated with an adjusted HR [95%CI] of 1.61 [0.98-2.65] and 3.22 [1.89-5.51] for OS, and 1.59 [1.05-2.41] and 2.30 [1.52-3.50] for DFS. Effect modification for OS existed between HGP and MVI (p < 0.01). Non-desmoplastic MVI-positive patients had a 5-year OS of 36% (HR: 5.21 [2.68-10.12]), compared to 60% for desmoplastic regardless of MVI (HR: 2.12 [1.08-4.18]), and 86% in non-desmoplastic MVI-negative. CONCLUSION: HCCs in non-cirrhotic livers display HGPs which may be of prognostic importance, especially when combined with MVI.

Preoperative systemic chemotherapy alters the histopathological growth patterns of colorectal liver metastases.

Histopathological growth patterns (HGPs) are a reliable, reproducible, and strong prognostic biomarker that can be assessed on haematoxylin and eosin-stained sections of resected colorectal liver metastases (CRLM). Assessment estimates the relative fraction of the tumour-liver interface for each of the three growth patterns; the desmoplastic HGP reflects good prognosis. Whether preoperative chemotherapy affects the HGP is currently unclear. The present international multicentre study evaluates this in an original cohort of 877 consecutive patients treated in the Netherlands, an external validation cohort of 1,203 consecutive patients treated in the USA, and a post hoc analysis from the phase III randomised controlled European Organization for Research and Treatment of Cancer (EORTC) 40983 trial (n = 70). All patients underwent resection of CRLM with or without preoperative systemic chemotherapy. Trial patients were randomised between perioperative chemotherapy and resection or resection alone. HGPs were determined according to consensus guidelines and compared for preoperative treatment status. Data from three separate tumour regression grading systems were available for the trial cohort. These were correlated with HGP stratified for treatment arm. In the original cohort, the average presence of desmoplastic HGP was 43% for chemo-naïve versus 67% for preoperatively treated patients (p < 0.001). A significant association between chemotherapy and desmoplastic HGP was found on multivariable analysis (ß [95% confidence interval, CI]: 24.57 [18.28-30.87], p < 0.001). In the validation cohort, the average presence of desmoplastic HGP was 40% for chemo-naïve versus 63% for preoperatively treated patients (p < 0.001). This association remained on multivariable analysis (ß [95% CI]: 24.18 [18.70-29.66], p < 0.001). In the EORTC 40983 trial, the average desmoplastic HGP presence was 33% in the resection arm versus 61% in the chemotherapy arm (p = 0.005). Chemotherapy was independently associated with an increase in desmoplastic HGP (ß [95% CI]: 23.29 [1.78-44.79], p = 0.022). All three tumour regression gradings were significantly associated with the desmoplastic HGP in the chemotherapy arm (all p < 0.04). None were associated in the resection arm (all p > 0.11). Preoperative chemotherapy induces histopathological changes that alter the HGP of CRLM.

Distinguishing pure histopathological growth patterns of colorectal liver metastases on CT using deep learning and radiomics: a pilot study.

Histopathological growth patterns (HGPs) are independent prognosticators for colorectal liver metastases (CRLM). Currently, HGPs are determined postoperatively. In this study, we evaluated radiomics for preoperative prediction of HGPs on computed tomography (CT), and its robustness to segmentation and acquisition variations. Patients with pure HGPs [i.e. 100% desmoplastic (dHGP) or 100% replacement (rHGP)] and a CT-scan who were surgically treated at the Erasmus MC between 2003-2015 were included retrospectively. Each lesion was segmented by three clinicians and a convolutional neural network (CNN). A prediction model was created using 564 radiomics features and a combination of machine learning approaches by training on the clinician's and testing on the unseen CNN segmentations. The intra-class correlation coefficient (ICC) was used to select features robust to segmentation variations; ComBat was used to harmonize for acquisition variations. Evaluation was performed through a 100 × random-split cross-validation. The study included 93 CRLM in 76 patients (48% dHGP; 52% rHGP). Despite substantial differences between the segmentations of the three clinicians and the CNN, the radiomics model had a mean area under the curve of 0.69. ICC-based feature selection or ComBat yielded no improvement. Concluding, the combination of a CNN for segmentation and radiomics for classification has potential for automatically distinguishing dHGPs from rHGP, and is robust to segmentation and acquisition variations. Pending further optimization, including extension to mixed HGPs, our model may serve as a preoperative addition to postoperative HGP assessment, enabling further exploitation of HGPs as a biomarker.

Histopathological Growth Patterns and Survival After Resection of Colorectal Liver Metastasis: An External Validation Study.

Background: After resection of colorectal cancer liver metastases (CRLM), 2 main histopathological growth patterns can be observed: a desmoplastic and a nondesmoplastic subtype. The desmoplastic subtype has been associated with superior survival. These findings require external validation. Methods: An international multicenter retrospective cohort study was conducted in patients treated surgically for CRLM at 3 tertiary hospitals in the United States and the Netherlands. Determination of histopathological growth patterns was performed on hematoxylin and eosin-stained sections of resected CRLM according to international guidelines. Patients displaying a desmoplastic histopathological phenotype (only desmoplastic growth observed) were compared with patients with a nondesmoplastic phenotype (any nondesmoplastic growth observed). Cutoff analyses on the extent of nondesmoplastic growth were performed. Overall survival (OS) and disease-free survival (DFS) were estimated using Kaplan-Meier and multivariable Cox analysis. All statistical tests were 2-sided. Results: In total 780 patients were eligible. A desmoplastic phenotype was observed in 19.1% and was associated with microsatellite instability (14.6% vs 3.6%, P = .01). Desmoplastic patients had superior 5-year OS (73.4%, 95% confidence interval [CI] = 64.1% to 84.0% vs 44.2%, 95% CI = 38.9% to 50.2%, P < .001) and DFS (32.0%, 95% CI = 22.9% to 44.7% vs 14.7%, 95% CI = 11.7% to 18.6%, P < .001) compared with their nondesmoplastic counterparts. A desmoplastic phenotype was associated with an adjusted hazard ratio for death of 0.36 (95% CI = 0.23 to 0.58) and 0.50 (95% CI = 0.37 to 0.66) for cancer recurrence. Prognosis was independent of KRAS and BRAF status. The cutoff analyses found no prognostic relationship between either OS or DFS and the extent of nondesmoplastic growth observed (all P > .1). Conclusions: This external validation study confirms the remarkably good prognosis after surgery for CRLM in patients with a desmoplastic phenotype. The extent of nondesmoplastic growth does not affect prognosis.

Oncological outcome, postoperative complications, and mammographic changes after intraoperative radiotherapy with electrons (IOERT) as a boost in a large single-institution cohort of breast cancer patients.

Advantages of using intraoperative radiotherapy with electrons (IOERT) as a boosting modality in breast-conserving therapy include the direct visualization of the tumor bed, a reduced skin dose, and patient convenience. We report oncological outcome, postoperative complication rate, and mammographic changes on follow-up imaging in women treated at our institution with IOERT as a boost modality in breast-conserving therapy for early-stage breast carcinoma. Between January 2007 and June 2018, 763 consecutive patients were enrolled. During breast-conserving surgery, an IOERT boost of 9 Gy was applied, followed by whole breast irradiation (WBI). At a median follow-up of 62.2 months (range: 0.5-135), 13 in-breast recurrences were observed, yielding a local tumor control rate of 98.4% at 5 years. In multivariable analysis, high tumor grading was predictive for local recurrence (HR = 5.6; 95%CI: 1.19-26.2). A total of 27 (3.5%) patients developed any kind of postoperative complication. None of the tumor characteristics nor any of the IOERT technical parameters were predictive for development of a postoperative complication. On follow-up imaging, 145 patients with mammographic changes BIRADS score ≥3 were found of which 50.3% required a biopsy. Only 17 patients had positive biopsies; none of the IOERT parameters were predictive for false-positive imaging. A 9 Gy IOERT boost combined with postoperative WBI provided outstanding local control rates, was well-tolerated, with limited postoperative complications. However, radiologists must be aware of a presumable higher prevalence of mammographic changes after IORT as a boost.

Histopathological growth patterns as biomarker for adjuvant systemic chemotherapy in patients with resected colorectal liver metastases.

Adjuvant systemic chemotherapy (CTx) is widely administered in patients with colorectal liver metastases (CRLM). Histopathological growth patterns (HGPs) are an independent prognostic factor for survival after complete resection. This study evaluates whether HGPs can predict the effectiveness of adjuvant CTx in patients with resected CRLM. Two main types of HGPs can be distinguished; the desmoplastic type and the non-desmoplastic type. Uni- and multivariable analyses for overall survival (OS) and disease-free survival (DFS) were performed, in both patients treated with and without preoperative chemotherapy. A total of 1236 patients from two tertiary centers (Memorial Sloan Kettering Cancer Center, New York, USA; Erasmus MC Cancer Institute, Rotterdam, The Netherlands) were included (period 2000-2016). A total of 656 patients (53.1%) patients received preoperative chemotherapy. Adjuvant CTx was only associated with a superior OS in non-desmoplastic patients that had not been pretreated (adjusted hazard ratio (HR) 0.52, 95% confidence interval (CI) 0.37-0.73, p < 0.001), and not in desmoplastic patients (adjusted HR 1.78, 95% CI 0.75-4.21, p = 0.19). In pretreated patients no significant effect of adjuvant CTx was observed, neither in the desmoplastic group (adjusted HR 0.83, 95% CI 0.49-1.42, p = 0.50) nor in the non-desmoplastic group (adjusted HR 0.96, 95% CI 0.71-1.29, p = 0.79). Similar results were found for DFS, with a superior DFS in non-desmoplastic patients treated with adjuvant CTx (HR 0.71, 95% CI 0.55-0.93, p < 0.001) that were not pretreated. Adjuvant CTx seems to improve OS and DFS after resection of non-desmoplastic CRLM. However, this effect was only observed in patients that were not treated with chemotherapy.

Enrichment of the tumour immune microenvironment in patients with desmoplastic colorectal liver metastasis.

BACKGROUND: Patients with resected colorectal liver metastasis (CRLM) who display only the desmoplastic histopathological growth pattern (dHGP) exhibit superior survival compared to patients with any non-desmoplastic growth (non-dHGP). The aim of this study was to compare the tumour microenvironment between dHGP and non-dHGP. METHODS: The tumour microenvironment was investigated in three cohorts of chemo-naive patients surgically treated for CRLM. In cohort A semi-quantitative immunohistochemistry was performed, in cohort B intratumoural and peritumoural T cells were counted using immunohistochemistry and digital image analysis, and in cohort C the relative proportions of individual T cell subsets were determined by flow cytometry. RESULTS: One hundred and seventeen, 34, and 79 patients were included in cohorts A, B, and C, with dHGP being observed in 27%, 29%, and 15% of patients, respectively. Cohorts A and B independently demonstrated peritumoural and intratumoural enrichment of cytotoxic CD8+ T cells in dHGP, as well as a higher CD8+/CD4+ ratio (cohort A). Flow cytometric analysis of fresh tumour tissues in cohort C confirmed these results; dHGP was associated with higher CD8+ and lower CD4+ T cell subsets, resulting in a higher CD8+/CD4+ ratio. CONCLUSION: The tumour microenvironment of patients with dHGP is characterised by an increased and distinctly cytotoxic immune infiltrate, providing a potential explanation for their superior survival.

Pathological features of vessel co-option versus sprouting angiogenesis.

Cancer cells can use existing blood vessels to acquire a vasculature. This process is termed 'vessel co-option'. Vessel co-option is an alternative to the growth of new blood vessels, or angiogenesis, and is adopted by a wide range of human tumour types growing within numerous tissues. A complementary aspect of this process is extravascular migratory tumour spread using the co-opted blood vessels as a trail. Vessel co-opting tumours can be discriminated from angiogenic tumours by specific morphological features. These features give rise to distinct histopathological growth patterns that reflect the interaction of cancer cells with the microenvironment of the organ in which they thrive. We will discuss the histopathological growth patterns of vessel co-option in the brain, the liver and the lungs. The review will also highlight evidence for the potential clinical value of the histopathological growth patterns of cancer. Vessel co-option can affect patient outcomes and resistance to cancer treatment. Insight into the biological drivers of this process of tumour vascularization will yield novel therapeutic strategies.

Histopathological growth patterns and positive margins after resection of colorectal liver metastases.

BACKGROUND: Histopathological growth patterns (HGPs) of colorectal liver metastases (CRLM) may be an expression of biological tumour behaviour impacting the risk of positive resection margins. The current study aimed to investigate whether the non-desmoplastic growth pattern (non-dHGP) is associated with a higher risk of positive resection margins after resection of CRLM. METHODS: All patients treated surgically for CRLM between January 2000 and March 2015 at the Erasmus MC Cancer Institute and between January 2000 and December 2012 at the Memorial Sloan Kettering Cancer Center were considered for inclusion. RESULTS: Of all patients (n = 1302) included for analysis, 13% (n = 170) had positive resection margins. Factors independently associated with positive resection margins were the non-dHGP (odds ratio (OR): 1.79, 95% confidence interval (CI): 1.11-2.87, p = 0.016) and a greater number of CRLM (OR: 1.15, 95% CI: 1.08-1.23 p < 0.001). Both positive resection margins (HR: 1.41, 95% CI: 1.13-1.76, p = 0.002) and non-dHGP (HR: 1.57, 95% CI: 1.26-1.95, p < 0.001) were independently associated with worse overall survival. CONCLUSION: Patients with non-dHGP are at higher risk of positive resection margins. Despite this association, both positive resection margins and non-dHGP are independent prognostic indicators of worse overall survival.

Angiotropism, pericytic mimicry and extravascular migratory metastasis: an embryogenesis-derived program of tumor spread.

Intravascular dissemination of tumor cells is the accepted mechanism of cancer metastasis. However, the phenomenon of angiotropism, pericyte mimicry (PM), and extravascular migratory metastasis (EVMM) has questioned the concept that tumor cells metastasize exclusively via circulation within vascular channels. This new paradigm of cancer spread and metastasis suggests that metastatic cells employ embryonic mechanisms for attachment to the abluminal surfaces of blood vessels (angiotropism) and spread via continuous migration, competing with and replacing pericytes, i.e., pericyte mimicry (PM). This is an entirely extravascular phenomenon (i.e., extravascular migratory metastasis or EVMM) without entry (intravasation) into vascular channels. PM and EVMM have mainly been studied in melanoma but also occur in other cancer types. PM and EVMM appear to be a reversion to an embryogenesis-derived program. There are many analogies between embryogenesis and cancer progression, including the important role of laminins, epithelial-mesenchymal transition, and the re-activation of embryonic signals by cancer cells. Furthermore, there is no circulation of blood during the first trimester of embryogenesis, despite the fact that there is extensive migration of cells to distant sites and formation of organs and tissues during this period. Embryonic migration therefore is a continuous extravascular migration as are PM and EVMM, supporting the concept that these embryonic migratory events appear to recur abnormally during the metastatic process. Finally, the perivascular location of tumor cells intrinsically links PM to vascular co-option. Taken together, these two new paradigms may greatly influence the development of new effective therapeutics for metastasis. In particular, targeting embryonic factors linked to migration that are detected during cancer metastasis may be particularly relevant to PM/EVMM.