[68Ga]Ga-PSMA and [68Ga]Ga-RM2 PET/MRI vs. Histopathological Images in Prostate Cancer: A New Workflow for Spatial Co-Registration.

This study proposed a new workflow for co-registering prostate PET images from a dual-tracer PET/MRI study with histopathological images of resected prostate specimens. The method aims to establish an accurate correspondence between PET/MRI findings and histology, facilitating a deeper understanding of PET tracer distribution and enabling advanced analyses like radiomics. To achieve this, images derived by three patients who underwent both [68Ga]Ga-PSMA and [68Ga]Ga-RM2 PET/MRI before radical prostatectomy were selected. After surgery, in the resected fresh specimens, fiducial markers visible on both histology and MR images were inserted. An ex vivo MRI of the prostate served as an intermediate step for co-registration between histological specimens and in vivo MRI examinations. The co-registration workflow involved five steps, ensuring alignment between histopathological images and PET/MRI data. The target registration error (TRE) was calculated to assess the precision of the co-registration. Furthermore, the DICE score was computed between the dominant intraprostatic tumor lesions delineated by the pathologist and the nuclear medicine physician. The TRE for the co-registration of histopathology and in vivo images was 1.59 mm, while the DICE score related to the site of increased intraprostatic uptake on [68Ga]Ga-PSMA and [68Ga]Ga-RM2 PET images was 0.54 and 0.75, respectively. This work shows an accurate co-registration method for histopathological and in vivo PET/MRI prostate examinations that allows the quantitative assessment of dual-tracer PET/MRI diagnostic accuracy at a millimetric scale. This approach may unveil radiotracer uptake mechanisms and identify new PET/MRI biomarkers, thus establishing the basis for precision medicine and future analyses, such as radiomics.

Infiltrative Growth Predicts the Risk of Recurrence After Surgery in Well-Differentiated Non-Functioning Pancreatic Neuroendocrine Tumors.

The incidence of well-differentiated non-functioning pancreatic neuroendocrine tumors (NF-PanNET) increased during the last decades. The risk of relapse after curative surgery, albeit low, is not negligible; moreover, adjuvant treatment is currently not an option and a reliable predictive model based on prognostic characteristics is urgently needed for tailoring a follow-up strategy. The histological classification of PanNET now relies only on the proliferative activity (mitosis and Ki67) and staging. In contrast to other endocrine neoplasms, the role of infiltrative growth pattern in NF-PanNET is not taken into consideration at present. In the current study, 247 consecutive patients who underwent surgical resection for a NF-PanNET were examined for the histological growth pattern of the tumor. Two distinct patterns (non-infiltrative vs. infiltrative) were described with the latter being further subclassified according to the type of structures invaded by the tumor (non-infiltrative: pattern 1; infiltration of adjacent pancreatic parenchyma and/or peripancreatic soft tissue: pattern 2; invasion of nearby organs and/or major vessels: pattern 3). The infiltrative growth resulted to be strongly associated with a poorer survival compared to a non-infiltrative growth (p < 0.001). In particular, the distinction between pancreatic parenchyma and/or peripancreatic soft tissue invasion versus adjacent organs and/or major vessels invasion was the most powerful predictor of recurrence after surgery at multivariate analysis (pattern 2 vs. pattern 1: HR 10.136, p = 0.028; pattern 3 vs. pattern 1: HR 15.775, p = 0.015). The infiltrative growth pattern could therefore provide additional prognostic information implementing the current grading and staging system.

Total embedding of spermatic cord and hilar soft tissue in orchiectomy for seminoma: does the extensive sampling improve pathologic risk factors?

Pure seminomas represent the majority of testicular germ cell tumors and accurate diagnosis and staging require an accurate sampling of radical orchiectomy specimens. The aim of our study is to find the most informative gross sampling method for orchiectomy specimens. We performed the extensive sampling of 88 radical orchiectomy specimens embedding in their entirety testicular hilum, rete testis, hilar soft tissue, and spermatic cord. We examined the impact of this procedure on tumor stage, prognostic parameters (lymphovascular invasion and infiltration of rete testis, epididymis, tunica vaginalis, and spermatic cord), and their relationship with recurrence. Eighty-eight seminomas from 88 radical orchiectomies were sampled. Seventy-seven cases (87.5%) presented as clinical stage I and 11 cases (12.5%) as clinical stage II. The follow-up period range was 18-54 months and 82 patients (93.2%) had a minimum of 2-year follow-up. Tumor size ranged from 0.4 to 16 cm (mean 3.6) requiring a mean of 7.1 sections for entire tumoral sampling. Epididymis required 2 to 8 sections (mean 3.3), and hilum and hilar soft tissues 2 to 9 sections (mean 3.4). Epididymal infiltration and lymphovascular invasion resulted significant at multivariate analysis generating a receiver operating characteristic (ROC) curve with area under curve of 0.778. All the other parameters (except for pagetoid rete testis infiltration) were significant to predict metastasis only at univariate analysis. Extensive sampling of radical orchiectomy specimens does not improve the accuracy of staging in pure seminomas. Lymphovascular invasion and epididymal infiltration are useful to predict metastasis.