[Thymoma and squamous thymic carcinoma diagnosis; experience from the RYTHMIC network]. / Diagnostic des thymomes et carcinomes thymiques malpighiens ; expérience du réseau RYTHMIC.

The RYTHMIC network, supported by the French National Cancer Institute is dedicated to the management of patients with thymic epithelial tumors through regional and national multidisciplinary tumor boards. Tumor board decisions are based on the initial pathology diagnoses. However, following clinical inclusion in the network, a central pathology review is organized, implicating a panel of pathologists, for histotype and stage classification, which is different from a classical second opinion from pathologist to pathologist for a difficult case. Thanks to the participation of all French pathologists, more than 1000 cases have been reviewed by the panel. The aim of this review is to share with the French pathology community, the experience of the group. It underlines the importance of macroscopy and surgeon-pathologist involvement to allow a good central review, the main histopathological and immunophenotypical patterns of the most frequent thymomas and thymic carcinoma types, the differential diagnoses, as well as the difficulties for the panel to reproducibly assess on slides, stage, for some cases.

[Authorization of pathologists for the estimation of the tumor cell percentage on tissue sample for molecular analysis purpose]. / Habilitation des pathologistes pour l'évaluation du pourcentage de cellules tumorales lors du contrôle morphologique avant extraction d'acides nucléiques.

Before molecular analysis is performed, morphological control with an estimation of the tumour cell percentage (%TC) could have a major impact on mutation detection. Accreditation according to NF EN ISO 15189 commands an authorization through evaluation of skills. The objective of this work was to validate the empowerment of pathologists to estimate %TC in tissue sample prior to molecular analysis. The accreditation technical guidance methods in Medical biology and histopathology were taken as references. %TC was the ratio of tumour cell nuclei on all nuclei within the area selected for the DNA extraction. External evaluations quality scores were used for accuracy. In order to assess the intermediate precision, 35 %TC estimation were performed 15 days apart in 4 samples (biopsies, transparietal biopsies or surgical specimen, either fixed or frozen) by 7 pathologists. Three other cases with interference (inflammation, mucus, necrosis) were evaluated. A result was satisfactory if %TC were within ±20 % of expected percentage obtained by the average of 35 estimates. The performances were satisfactory since no estimate was made more than 20 % of the expected percentage. Low interpathologists reproducibility has been reported in the literature and can have a consequence on molecular analysis in samples with low %TC, where the value reach the analytical sensitivity thresholds of molecular techniques. The current report is an example of a step of the accreditation process, which is a challenge for pathologists' activity in the future.

Granulosa cell tumor of the ovary with high FDG uptake.

Granulosa cell tumor (GCT) of the ovary is a rare tumor accounting for 2%-5% of ovarian malignancies. Although the usefulness of 18F-FDG PET/CT is well demonstrated in the staging and follow-up of the great majority of ovarian cancers, GCTs are known to cause false-negative results on FDG PET because of very low FDG avidity. We present a case of a GCT in which an 18F-FDG PET/CT proved very useful in the detection of recurrence.