Retrospective Evaluation of the Prognostic Value of Histological Growth Pattern in Patients with Colorectal Peritoneal Metastases Undergoing Curative-Intent Cytoreductive Surgery.

BACKGROUND: Two distinct histological growth patterns (HGPs) were described in patients with peritoneal metastasis of colorectal cancer origin (PMCRC) with limited Peritoneal Cancer Index (PCI) ≤ 6 who did not receive neoadjuvant chemotherapy (NAC) and were treated with cytoreductive surgery (CRS) ± hyperthermic intraperitoneal chemotherapy (HIPEC): pushing HGP (P-HGP) and infiltrating HGP (I-HGP). Patients with dominant P-HGP (> 50%) had significantly better disease-free survival (DFS) and overall survival (OS). OBJECTIVE: We aimed to determine whether these previous observations regarding the prognostic value of HGP in patients with PMCRC with low PCI (≤ 6) are also valid in all operable patients, regardless of whether they received NAC or not and regardless of PCI score. METHODS: This was a retrospective study including 76 patients who underwent complete CRS ± HIPEC for PMCRC between July 2012 and March 2019. In each patient, up to five of the largest excised peritoneal nodules were analyzed for their tumor-to-peritoneum interface. Correlations between NAC, HGP, and prognosis were further explored. RESULTS: Thirty-seven patients (49%) had dominant P-HGP and 39 (51%) had dominant I-HGP. On univariate analysis, patients with P-HGP ≤ 50% had significantly lower OS than those with dominant P-HGP > 50% (39 versus 60 months; p = 0.014) confirmed on multivariate analysis (hazard ratio 2.4, 95% confidence interval 1.3-4.5; p = 0.006). There were no significant associations between NAC and type of HGP. CONCLUSIONS: This study confirms the prognostic value and reproducibility of the two previously reported HGPs in PMCRC. Dominant P-HGP is associated with better DFS and OS in patients undergoing curative-intent CRS ± HIPEC compared with I-HGP, independently of the extent of peritoneal disease burden.

Molecular differences of angiogenic versus vessel co-opting colorectal cancer liver metastases at single-cell resolution.

BACKGROUND: Colorectal cancer liver metastases (CRCLM) are associated with a poor prognosis, reflected by a five-year survival rate of 14%. Anti-angiogenic therapy through anti-VEGF antibody administration is one of the limited therapies available. However, only a subgroup of metastases uses sprouting angiogenesis to secure their nutrients and oxygen supply, while others rely on vessel co-option (VCO). The distinct mode of vascularization is reflected by specific histopathological growth patterns (HGPs), which have proven prognostic and predictive significance. Nevertheless, their molecular mechanisms are poorly understood. METHODS: We evaluated CRCLM from 225 patients regarding their HGP and clinical data. Moreover, we performed spatial (21,804 spots) and single-cell (22,419 cells) RNA sequencing analyses to explore molecular differences in detail, further validated in vitro through immunohistochemical analysis and patient-derived organoid cultures. RESULTS: We detected specific metabolic alterations and a signature of WNT signalling activation in metastatic cancer cells related to the VCO phenotype. Importantly, in the corresponding healthy liver of CRCLM displaying sprouting angiogenesis, we identified a predominantly expressed capillary subtype of endothelial cells, which could be further explored as a possible predictor for HGP relying on sprouting angiogenesis. CONCLUSION: These findings may prove to be novel therapeutic targets to the treatment of CRCLM, in special the ones relying on VCO.

Immunohistochemical characterisation of the immune landscape in primary uveal melanoma and liver metastases.

BACKGROUND: The immune landscape of uveal melanoma liver metastases (UMLM) has not been sufficiently studied. METHODS: Immune cell infiltrates (ICIs), PD-1 and PD-L1 were characterised in 62 UMLM and 28 primary uveal melanomas (PUM). ICI, PD-1 and PD-L1 were scored as: (1) % tumoral area occupied by tumour-infiltrating lymphocytes or macrophages (TILs, TIMs) and (2) % perTumoral (perT) area. ICIs and other variables including histopathologic growth patterns (HGPs), replacement and desmoplastic, of UMLM were analysed for their prognostic value. RESULTS: ICIs recognised by haematoxylin-eosin-saffron (HES) and IHC (e.g., T cells (CD3), B cells (CD20). Macrophages (CD68), (CD163), were primarily localised to the perT region in PUM and UMLM and were more conspicuous in UMLM. HES, CD3, CD4, FoxP3, CD8, CD20, PD-1 TILs were scant (<5%). TIMs were more frequent, particularly in UMLM than in PUM. Both CD68+ TIMs and HGPs remained significant on multivariate analysis, influencing overall (OS) and metastasis-specific overall survival (MSOS). CD68 + , CD163+ and CD20+ perT infiltrates in UMLM predicted increased OS and MSOS on univariate analysis. CONCLUSIONS: TILs and PD-L1 have no predictive value in PUM or UMLM. CD68+ and CD163+TIMs, CD20+ perT lymphocytes, and HGPs are important prognostic factors in UMLMs.

The Prognostic Value of Distinct Histological Growth Patterns of Colorectal Peritoneal Metastases: A Pilot Study.

BACKGROUND: Different histological growth patterns (HGP) describing the tumor-to-liver interface have been described in colorectal liver metastases and have been associated with a strong prognostic value. However, HGP of peritoneal metastases (PM) of colorectal cancer (CRC) have not yet been described. Our objective was to determine whether distinct HGP can be identified in PMCRC and to evaluate their potential prognostic value in these patients. METHODS: This retrospective study included 38 patients who underwent curative-intent surgery for PMCRC between July 2012 and March 2019, with PCI≤6, and who had not received preoperative chemotherapy. In each patient, the tumor-to-peritoneum interface was evaluated in the excised peritoneal nodules. The association between HGP and postoperative survival was analyzed by using the Kaplan-Meier method. RESULTS: Two distinct HGP were identified: a pushing-type (P-HGP), characterized by a fibrous rim separating the PM and peritoneum, and an infiltrating-type (I-HGP), characterized by focal penetration of tumor cells into the surrounding peritoneal lining without a fibrous rim. Fifteen patients had dominant P-HGP, and 23 patients had dominant I-HGP. Patients with dominant P-HGP (>50% tumor-peritoneum interface) had a significantly better DFS (30 months) than those with P-HGP <50% (9 months; p = 0.029). Patients with a P-HGP dominance >60% had better OS (131 months) than those with P-HGP <60% (41 months; p = 0.044). CONCLUSIONS: This is the first description of two distinct, reproducible HGP in PMCRC. The dominant P-HGP is associated with a favorable prognosis in patients with PMCRC, compared with I-HGP, suggesting that this parameter could ultimately represent a new prognostic biomarker.

Can medical imaging identify the histopathological growth patterns of liver metastases?

The histopathological growth patterns (HGPs) of liver metastases of colorectal cancer and of several other tumor types predict outcome of patients in multiple studies. The HGPs of liver metastases have a prognostic but also a predictive value with one of the growth patterns, the replacement growth pattern, related to resistance to systemic treatment. Given that the HGP can only be assessed in a reliable manner when a surgical resection of the metastasis has been performed, this biomarker cannot be exploited to the full. For example, HGPs can at this moment, not be used to decide whether patients with liver metastatic breast or colorectal cancer will benefit or not from locoregional treatment, such as surgery or radiotherapy, and from peri-operative systemic treatment. In this review we highlight studies that suggest that the HGPs of liver metastases can be identified by medical imaging. Although still to be confirmed by a prospective multicenter approach, some studies indeed achieve a high accuracy in predicting the HGPs by applying radiomic algorithms on CT- or MR-images of liver metastases. This is an important step towards a treatment planning of patients with liver metastatic cancer that takes into account the biology and the progression kinetics of the metastases.

L1CAM and laminin vascular network: Association with the high-risk replacement histopathologic growth pattern in uveal melanoma liver metastases.

The replacement histopathologic growth pattern (rHGP) in melanoma liver metastases connotes an aggressive phenotype (vascular co-option; angiotropic extravascular migratory spread) and adverse prognosis. Herein, replacement and desmoplastic HGP (dHGP) were studied in uveal melanoma liver metastases (MUM). In particular, L1CAM and a "laminin vascular network" were detected at the advancing front of 14/20 cases (p = 0.014) and 16/20 cases (p = 6.4e-05) rHGPs, respectively, but both were absent in the dHGP (8/8 cases) (p = 0.014, and p = 6.3e-05, respectively). L1CAM highlighted progressive extension of angiotropic melanoma cells along sinusoidal vessels in a pericytic location (pericytic mimicry) into the hepatic parenchyma. An inverse relationship between L1CAM expression and melanin index (p = 0.012) suggested differentiation toward an amelanotic embryonic migratory phenotype in rHGP. Laminin labeled the basement membrane zone interposed between sinusoidal vascular channels and angiotropic melanoma cells at the advancing front. Other new findings: any percentage of rHGP and pure rHGP had a significant adverse effect on metastasis-specific overall survival (p = 0.038; p = 0.0064), as well as predominant rHGP (p = 0.0058). Pure rHGP also was associated with diminished metastasis-free survival relative to dHGP (p = 0.040), possibly having important implications for mechanisms of tumor spread. In conclusion, we report for the first time that L1CAM and a laminin vascular network are directly involved in this high-risk replacement phenotype. Further, this study provides more detailed information about the adverse prognostic effect of the rHGP in MUM.

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.

Prognostic implications of adaptive immune features in MMR-proficient colorectal liver metastases classified by histopathological growth patterns.

BACKGROUND: After resection, colorectal cancer liver metastases (CRLM) surrounded by a desmoplastic rim carry a better prognosis than the metastases replacing the adjacent liver. However, these histopathological growth patterns (HGPs) are insufficient to guide clinical decision-making. We explored whether the adaptive immune features of HGPs could refine prognostication. METHODS: From 276 metastases resected in 176 patients classified by HGPs, tissue microarrays were used to assess intratumoral T cells (CD3), antigen presentation capacity (MHC class I) and CD73 expression producing immunosuppressive adenosine. We tested correlations between these variables and patient outcomes. RESULTS: The 101 (57.4%) patients with dominant desmoplastic HGP had a median recurrence-free survival (RFS) of 17.1 months compared to 13.3 months in the 75 patients (42.6%) with dominant replacement HGP (p = 0.037). In desmoplastic CRLM, high vs. low CD73 was the only prognostically informative immune parameter and was associated with a median RFS of 12.3 months compared to 26.3, respectively (p = 0.010). Only in dominant replacement CRLM, we found a subgroup (n = 23) with high intratumoral MHC-I expression but poor CD3+ T cell infiltration, a phenotype associated with a short median RFS of 7.9 months. CONCLUSIONS: Combining the assessments of HGP and adaptive immune features in resected CRLM could help identify patients at risk of early recurrence.

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.

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.

Circulating tumor cell detection: A prospective comparison between CellSearch® and RareCyte® platforms in patients with progressive metastatic breast cancer.

PURPOSE: Circulating tumor cells (CTCs) are prognostic in patients with breast cancer. Several technical platforms exist for their enumeration and characterization. Comparative studies between these platforms are scarce. The RareCyte CTC detection is theoretically more sensitive than the established CellSearch platform, which identifies only CTCs that express EpCAM and cytokeratin. This study prospectively compares CTC enumeration in patients with breast cancer in a paired analysis using these two platforms. It investigates survival outcomes in groups defined by a CTC count threshold. DESIGN: CTC enumeration was performed on 100 samples obtained from 86 patients with progressive metastatic breast cancer (MBC) in two independent laboratories each blinded to the clinical data and the results from the other platform. RESULTS: One hundred paired samples were collected and CTC counts were determined using the CellSearch and RareCyte CTC platforms. In total, 65% and 75% of samples had at least one detectable CTC in 7.5 mL blood with the CellSearch and the RareCyte systems, respectively. CTC counts with the CellSearch system ranged from 0 to 2289 with a median of 3 CTCs, the RareCyte CTC counts ranged from 0 to 1676 with a median of 3 CTCs. The number of samples with 5 or more CTCs in 7.5 mL of blood (the poor prognosis cut-off validated with the CellSearch system) blood was 45% with the CellSearch test and 48% with the RareCyte test. CTC counts quantified with the CellSearch and the RareCyte systems were strongly correlated (Spearman's r = 0.8235 (0.7450-0.8795) p < 0.001). 86 patients were included for Kaplan-Meier survival analysis. An increased mortality risk in patients with CellSearch of 5 CTCs or more per 7.5 mL blood, with a log-rank hazard ratio of 5.164 (2.579-10.34) (p < 0.001) was confirmed. The survival analysis with RareCyte CTC counts with the identical cut-off showed a significantly impaired survival with a hazard ratio of 4.213 (2.153-8.244) (p < 0.001). CONCLUSION: Our data demonstrate the analytical and prognostic equivalence of CellSearch and RareCyte CTC enumeration platforms in patients with MBC using the CellSearch cut-off. This is the first demonstration of prognostic significance using the RareCyte platform.

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.

Accuracy of high-risk HPV DNA PCR, p16(INK4a) immunohistochemistry or the combination of both to diagnose HPV-driven oropharyngeal cancer.

BACKGROUND: The incidence of high-risk human papillomavirus (hrHPV)-driven head and neck squamous cell carcinoma, in particular oropharyngeal cancers (OPC), is increasing in high-resource countries. Patients with HPV-induced cancer respond better to treatment and consequently have lower case-fatality rates than patients with HPV-unrelated OPC. These considerations highlight the importance of reliable and accurate markers to diagnose truly HPV-induced OPC. METHODS: The accuracy of three possible test strategies, i.e. (a) hrHPV DNA PCR (DNA), (b) p16(INK4a) immunohistochemistry (IHC) (p16), and (c) the combination of both tests (considering joint DNA and p16 positivity as positivity criterion), was analysed in tissue samples from 99 Belgian OPC patients enrolled in the HPV-AHEAD study. Presence of HPV E6*I mRNA (mRNA) was considered as the reference, indicating HPV etiology. RESULTS: Ninety-nine OPC patients were included, for which the positivity rates were 36.4%, 34.0% and 28.9% for DNA, p16 and mRNA, respectively. Ninety-five OPC patients had valid test results for all three tests (DNA, p16 and mRNA). Using mRNA status as the reference, DNA testing showed 100% (28/28) sensitivity, and 92.5% (62/67) specificity for the detection of HPV-driven cancer. p16 was 96.4% (27/28) sensitive and equally specific (92.5%; 62/67). The sensitivity and specificity of combined p16 + DNA testing was 96.4% (27/28) and 97.0% (65/67), respectively. In this series, p16 alone and combined p16 + DNA missed 1 in 28 HPV driven cancers, but p16 alone misclassified 5 in 67 non-HPV driven as positive, whereas combined testing would misclassify only 2 in 67. CONCLUSIONS: Single hrHPV DNA PCR and p16(INK4a) IHC are highly sensitive but less specific than using combined testing to diagnose HPV-driven OPC patients. Disease prognostication can be encouraged based on this combined test result.

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 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.

Clinico-metabolic characterization improves the prognostic value of histological growth patterns in patients undergoing surgery for colorectal liver metastases.

BACKGROUND AND OBJECTIVES: The histological growth pattern (HGP) represents a strong prognostic factor in patients undergoing surgery for colorectal liver metastases (CRLM). We evaluated whether the combination of HGP with clinico-metabolic parameters could improve its prognostic value. METHODS: In a series of 108 patients undergoing resection of CRLM, the HGP of CRLM was scored according to international guidelines. Baseline clinico-metabolic clinical status was evaluated using a metabolic-Clinical Risk Score (mCRS), combining traditional Memorial Sloan Kettering-CRS parameters with the tumor-to-liver glucose uptake ratio as measured with 18 Fluorodeoxyglucose/positron emission tomography. RESULTS: In patients with desmoplastic HGP (DHGP) CRLM (20% of all patients), 5- and 10-years overall survival (OS) and disease free survival (DFS) were 66% and 43% and 37% and 24.5%, as compared with 35% and 21% and 11% and 11% in the non-DHGP group (p = 0.07 and 0.054). Among DHGP patients, those with a low-risk mCRS had improved postoperative outcomes, 5- and 10-years OS and DFS reaching 83.3% and 62.5% and 50% and 33%, as compared with 18% and 0% and 0% and 0% in high-risk mCRS patients (p = 0.007 and 0.003). In contrast, mCRS did not influence postoperative survivals in non-DHGP patients. CONCLUSIONS: Combining the clinico-metabolic characteristics with the HGP may improve prognostication in patients undergoing surgery for CRLM.

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.

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.

Immune phenotype and histopathological growth pattern in patients with colorectal liver metastases.

BACKGROUND: Patients with desmoplastic (angiogenic) histopathological growth pattern (HGP) colorectal liver metastases (CLM) might derive more benefit from bevacizumab-based chemotherapy than those with replacement (non-angiogenic) HGP. This study investigated the association of HGP with the immune phenotype (IP) and clinical outcome after liver resection. METHODS: CLM of patients treated with perioperative bevacizumab-based chemotherapy and liver resection were investigated. Association of HGP and IP with response, recurrence-free survival (RFS) and overall survival (OS) was investigated. RESULTS: One hundred and eighteen patients (M/F 66/52, median age 62.3 (31.0-80.4) years, median follow-up 32.2 (5.0-92.7) months) were enrolled. The inflamed IP was associated with the desmoplastic HGP. The desmoplastic HGP was associated with better radiological and histological response compared to the replacement HGP, respectively. The replacement HGP was associated with shorter RFS (8.7 versus 16.3 months, HR 2.60, P = 0.001) and OS (36.6 months versus not reached, HR 2.32, P = 0.027), respectively. The non-inflamed IP was associated with shorter RFS (10.8 versus 16.5 months, HR 1.85, P = 0.029). The HGP but not the IP remained significant in multivariable analysis for RFS. CONCLUSIONS: The desmoplastic HGP is associated with the inflamed IP and HGP may be a potential biomarker for adjuvant treatment that includes targeting the immune contexture.

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.