Intraoperative frozen section evaluation of ovarian sex cord-stromal tumours and their mimics: a study of 121 cases with emphasis on potential diagnostic pitfalls.

Ovarian sex cord-stromal tumours (SCSTs) present diagnostic difficulties during frozen section (FS) consultations due to their diverse morphology. This study aimed to evaluate the accuracy of FS evaluation of SCSTs in our institution, as well as to examine the reasons leading to incorrect FS diagnosis. Cases mimicking SCSTs and diagnosed as such during FS were also highlighted. We analysed 121 ovarian SCST cases and their mimics which underwent FS consultations over a 10-year period, to evaluate FS accuracy, reasons for deferrals and discrepancies. FS diagnoses were concordant, deferred and discrepant compared to the final diagnosis in 50 (41.3%), 39 (32.2%) and 32 (26.5%) cases, respectively. Major discrepancies (9/121, 7.4%) were mostly related to the diagnosis of adult granulosa cell tumour (AGCT). A fibromatous AGCT was misinterpreted as fibroma on FS, while a cystic AGCT was called a benign cyst. Conversely, a mesonephric-like adenocarcinoma, a sertoliform endometrioid carcinoma and a thecoma were misinterpreted as AGCT on FS. Another discrepant case was a Krukenberg tumour with prominent fibromatous stroma in which malignant signet ring cells were overlooked and misinterpreted as fibroma. Minor discrepancies were primarily associated with fibroma (21/23, 91.3%), wherein minor but potentially impactful details such as cellular fibroma and mitotically active cellular fibroma were missed due to sampling issues and misinterpretation as leiomyoma. FS evaluation for ovarian SCSTs demonstrated an overall accuracy of 78.5%, 81.0% and 81.8% for benign, uncertain/low malignant potential and malignant categories, respectively. There was no FS-related adverse clinical impact in all cases with available follow-up information (120/121 cases). Intraoperative FS evaluation of ovarian SCSTs is challenging. A small number of cases were misinterpreted, with AGCTs being the primary group where errors occur. Awareness of common diagnostic pitfalls and difficulties, alongside application of a stepwise approach, including (1) obtaining comprehensive clinical information, (2) thorough macroscopic examination and directed sampling, (3) meticulous microscopic examination with consideration of pitfalls and mimics, (4) effective communication with surgeons in difficult cases, and (5) consultation of subspecialty colleagues in challenging cases, will enhance pathologists' reporting accuracy and management of such cases in the future.

Deciphering tumour microenvironment and elucidating the origin of cancer cells in ovarian clear cell carcinoma.

Ovarian clear cell carcinoma (CCC) has an East Asian preponderance. It is associated with endometriosis, a benign condition where endometrial (inner lining of the uterus) tissue is found outside the uterus and on the peritoneal surface, in the abdominal or pelvic space. CCC is relatively more resistant to conventional chemotherapy compared to other ovarian cancer subtypes and is associated with a poorer prognosis. In this study, we recruited and obtained tumour tissues from seven patients across the four stages of CCC. The tumour and the tumour microenvironment (TME) from 7 CCC patients spanning clinical stages 1-4 were transcriptionally profiled using high-resolution scRNA-seq to gain insight into CCC's biological mechanisms. Firstly, we built a scRNA-seq resource for the CCC tumour microenvironment (TME). Secondly, we identified the different cell type proportions and found high levels of immune infiltration in CCC. Thirdly, since CCC is associated with endometriosis, we compared CCC with two publicly available endometriosis scRNA-seq datasets. The CCC malignant cells showed similarities with glandular secretory and ciliated epithelial cells found in endometriosis. Finally, we determined the differences in cell-cell communication between various cell types present in CCC TME and endometriosis conditions to gain insights into the transformations in CCC.

Appendiceal diverticulosis: a harbinger of underlying primary appendiceal adenocarcinoma?

Diagnosis of primary appendiceal adenocarcinoma (PAA) is hindered by its rarity and largely asymptomatic nature. Appendiceal diverticulosis (AD) is equally rare. We report an unusual case of PAA presenting with perforated appendiceal diverticulitis, and discuss a review of the literature about its association, and its surgical and pathological implications. A middle-aged man was admitted with right iliac fossa (RIF) pain and a corresponding tender abdominal mass for 5 days. Computerised tomography (CT) scan demonstrated a thickened appendix with 3 cm abscess at its base. During laparoscopic appendicectomy, the appendiceal phlegmon was adhered to the surrounding bowel. Histology showed a perforated diverticulum near the appendiceal tip, and a primary appendiceal well-differentiated adenocarcinoma located proximal to it with clear margins. Up to 48% of ADs are associated with appendiceal neoplasms, but its coexistence with PAA is reported in fewer than ten instances worldwide. Obstructing appendiceal tumours, by raising intraluminal pressure, can predispose to AD formation. Intestinal-type PAA is often managed like its colorectal counterpart, although controversies about management of PAA in a perforated AD remain. Recognition of the association of AD and PAA is critical to ensure meticulous oncological resection and histological examination.