Magnetic Resonance Diffusion-Weighted Imaging for Detecting Fundal Intracholecystic Papillary Neoplasm inside Rokitansky-Aschoff Sinuses: A Comparison of Two Cases and a Literature Review

Rokitansky-Aschoff sinuses (RAS) are a common imaging finding in gallbladder adenomyomatosis (ADM), often presenting as fundal cystic spaces. Intracholecystic papillary neoplasm (ICPN) is a relatively uncommon pre-invasive tumor of the gallbladder epithelium that rarely involves RAS mucosa. We compare two cases that showed similar fundal cystic spaces resembling RAS, in which Magnetic Resonance Diffusion-Weighted Imaging (MR-DWI) was valuable for detecting (or ruling out) an underlying malignant ICPN. Evidence from the literature overall supports the role of MR-DWI for detecting intracholecystic malignant tissue.

PD-L1 Expression in Different Segments and Histological Types of Ovarian Cancer According to Lymphocytic Infiltrate

Background and Objectives: Ovarian cancer is the leading cause of death among gynecological tumors. PD-1/PD-L1 immunoregulatory mechanism is activated in ovarian cancers. Lymphocyte infiltration is a significant factor that affects its expression. We analyzed the correlation between localization of lymphocytic infiltrate and PD-L1 expression in epithelial ovarian tumors. Materials and Methods: PD-L1 expression was analyzed in 328 subjects, 122 with epithelial ovarian carcinoma, 42 with atypical proliferative tumor, and 164 with benign epithelial ovarian tumor. Expression in central and invasive tumor parts in epithelial ovarian carcinoma was combined with the most pronounced lymphocyte reaction. Immunohistochemical analysis was performed using the tissue microarray and correlated with a set of histopathology parameters. Results: PD-L1 expression was most prominent in epithelial ovarian carcinoma with different levels of expression observed between invasive and central tumor segments. A high level of PD-L1 expression on tumor cells was more frequently present in the invasive than in the central tumor parts (p < 0.001) only in high-grade serous ovarian carcinoma (HGSC). There was no significant correlation between peritumoral lymphocytic infiltrate and PD-L1 expression regardless of tumor segment. In the central tumor parts of HGSC, there was a correlation of intratumoral lymphocytic infiltrate with a higher level of PD-L1 expression (p = 0.003). Conclusions: The most prominent PD-L1 expression was observed in the invasive tumor parts of HGSC. Only the central parts of the HGSC exhibited significant PD-L1 expression in association with considerable intratumoral lymphocytic infiltrate.

CSIG-15. ALTERATIONS IN THE TRANSSULFURATION PATHWAY ENABLE GLIOBLASTOMA INVASION INTO THE PERITUMORAL WHITE MATTER

Glioblastoma is a primary malignant brain tumor with a median survival under two years. The poor prognosis glioblastoma caries is largely due to cellular invasion, which enables escape from resection and drives inevitable recurrence. While numerous factors have been proposed as the primary driving forces behind glioblastoma’s ability to invade adjacent tissues rapidly, little attention has been paid to the alterations in tumor cell metabolism needed for tumor cells to thrive in isolation in the peritumoral white matter. To improve on biased 2D cell culture studies, we defined the links between glioblastoma metabolism in invasion using unbiased CRISPR screens and metabolomics performed in biomimetic 3D hydrogels and regional biopsies of patient glioblastomas. Through these platforms, we identified targetable metabolic factors which drive cellular invasion in glioblastoma. Metabolomics revealed cystathionine to be selectively enriched in the invasive tumor front of both site-directed biopsies (6-fold change), and 3D organoid models (14-fold change). RNA sequencing revealed 7/30 (23%) metabolic genes upregulated in the invasive tumor front were involved in cysteine or glutathione metabolism. These results highlight a clear role of the transsulfuration pathway in glioblastoma invasion, revealing a targetable alteration unique to invading glioblastoma cells.

Tumor heterogeneity evaluated by computed tomography detects muscle-invasive upper tract urothelial carcinoma that is associated with inflammatory tumor microenvironment

To detect muscle-invasive upper tract urothelial carcinoma, we evaluated the internal texture of the tumor using texture analysis of computed tomography images in 86 cases of upper tract urothelial carcinoma. The internal texture of the tumor was evaluated as the value of computed tomography attenuation number of the unenhanced image, and the median, standard deviation, skewness and kurtosis were calculated. Each parameter was compared with clinicopathological factors, and their associations with postoperative prognosis were investigated. Immunohistochemistry was performed to investigate the histological and molecular mechanisms of the inflammatory tumor microenvironment. The histogram of computed tomography attenuation number in non-muscle invasive tumor was single-peaked, whereas muscle invasive tumor showed a multi-peaked shape. In the parameters obtained by texture analysis, standard deviation was significantly associated with pathological stage (p < 0.0001), tumor grade (p = 0.0053), lymphovascular invasion (p = 0.0078) and concomitant carcinoma in situ (p = 0.0177) along with recurrence-free (p = 0.0191) and overall survival (p = 0.0184). The standard deviation value correlated with the amount of stromal components (p < 0.0001) and number of tumor-infiltrating macrophages (p < 0.0001). In addition, higher expression of high mobility group box 1 was found in heterogeneous tumor. Tumor heterogeneity evaluated by texture analysis was associated with muscle-invasive upper tract urothelial carcinoma and represented an inflammatory tumor microenvironment and useful as the clinical assessment to differentiate muscle invasive tumor.

OTME-12. Role of the transsulfuration pathway in glioblastoma invasion

Glioblastoma (GBM) is a primary malignant brain tumor with a median survival under two years. The poor prognosis GBM caries is largely due to cellular invasion, which enables escape from resection and drives inevitable recurrence. Numerous factors have been proposed as the primary driving forces behind GBM’s ability to invade adjacent tissues rapidly, including alterations in the tumor’s cellular metabolism. Though studies have investigated links between GBM’s metabolic profile and its invasive capability, these studies have had two notable limitations. First, while infiltrating GBM cells extending beyond the tumor edge utilize adaptive cellular machinery to overcome stressors in their microenvironment, these cells at the invasive front have not been the ones sampled in invasive studies, which have used cell lines or banked tumor tissue taken from the readily accessible tumor core. Second, studies of invasion have primarily used two-dimensional (2D) culture systems, which fail to capture the dimensionality, mechanics, and heterogeneity of GBM invasion. To address these limitations, our team has developed two parallel approaches: acquisition of site-directed biopsies from patient GBMs to define regional heterogeneity in invasiveness, and engineering of 3D platforms to study invasion in vitro. Through utilization of these platforms, and by taking advantage of the system-wide, unbiased screens of metabolite profile and gene expression available, our team looks to identify targetable metabolic factors which drive cellular invasion in GBM. Untargeted metabolomics revealed cystathionine to be selectively enriched in the invasive tumor front of both site directed biopsies (fold change 5.8), and 3D organoid models (fold change 14.2). RNA sequencing revealed 7/30(23%) metabolic genes upregulated in the invasive tumor front were involved in cysteine or glutathione metabolism. These results highlight a clear role of the transsulfuration pathway in GBM invasion that our team looks to investigate with further targeted assays.

A Standardized Analysis of Tertiary Lymphoid Structures in Human Melanoma: Disease Progression- and Tumor Site-Associated Changes With Germinal Center Alteration

There is increasing evidence that tertiary lymphoid structures (TLS) control not only local adaptive B cell responses at melanoma tumor sites but also the cellular composition and function of other immune cells. In human melanoma, however, a comprehensive analysis of TLS phenotypes, density and spatial distribution at different disease stages is lacking. Here we used 7-color multiplex immunostaining of whole tissue sections from 103 human melanoma samples to characterize TLS phenotypes along the expression of established TLS-defining molecular and cellular components. TLS density and spatial distribution were determined by referring TLS counts to the tissue area within defined intra- and extratumoral perimeters around the invasive tumor front. We show that only a subgroup of primary human melanomas contains TLS. These TLS rarely formed germinal centers and mostly located intratumorally within 1 mm distance to the invasive tumor front. In contrast, melanoma metastases had a significantly increased density of secondary follicular TLS. They appeared preferentially in stromal areas within an extratumoral 1 mm distance to the invasive tumor front and their density varied over time and site of metastasis. Interestingly, secondary follicular TLS in melanoma often lacked BCL6+ lymphatic cells and canonical germinal center polarity with the formation of dark and light zone areas. Our work provides an integrated qualitative, quantitative and spatial analysis of TLS in human melanoma and shows disease progression- and site-associated changes in TLS phenotypes, density and spatial distribution. The frequent absence of canonical germinal center polarity in melanoma TLS highlights the induction of TLS maturation as a potential additive to future immunotherapy studies. Given the variable evaluation strategies used in previous TLS studies of human tumors, an important asset of this study is the standardized quantitative evaluation approach that provides a high degree of reproducibility.

Characterizing the Invasive Tumor Front of Aggressive Uterine Adenocarcinoma and Leiomyosarcoma

The invasive tumor front (the tumor–host interface) is vitally important in malignant cell progression and metastasis. Tumor cell interactions with resident and infiltrating host cells and with the surrounding extracellular matrix and secreted factors ultimately determine the fate of the tumor. Herein we focus on the invasive tumor front, making an in-depth characterization of reticular fiber scaffolding, infiltrating immune cells, gene expression, and epigenetic profiles of classified aggressive primary uterine adenocarcinomas (24 patients) and leiomyosarcomas (11 patients). Sections of formalin-fixed samples before and after microdissection were scanned and studied. Reticular fiber architecture and immune cell infiltration were analyzed by automatized algorithms in colocalized regions of interest. Despite morphometric resemblance between reticular fibers and high presence of macrophages, we found some variance in other immune cell populations and distinctive gene expression and cell adhesion-related methylation signatures. Although no evident overall differences in immune response were detected at the gene expression and methylation level, impaired antimicrobial humoral response might be involved in uterine leiomyosarcoma spread. Similarities found at the invasive tumor front of uterine adenocarcinomas and leiomyosarcomas could facilitate the use of common biomarkers and therapies. Furthermore, molecular and architectural characterization of the invasive front of uterine malignancies may provide additional prognostic information beyond established prognostic factors.