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.

Pituitary Carcinoma in a Patient with Cowden Syndrome.

BACKGROUND Pituitary carcinomas are rare tumors that are histologically indistinguishable from pituitary adenoma. This report describes an extremely rare case of pituitary carcinoma in a patient with clinically diagnosed Cowden syndrome (CS). CS is a rare multisystemic hereditary disease with increase risks of cancer and benign overgrowth of different types of tissues. CASE REPORT A 52-year-old woman with history of CS presented with pituitary adenoma and multiple meningiomata. After surgical resection, there was recurrence of the pituitary tumor. Partial resection of the recurrent pituitary tumor revealed an adenoma. Radiotherapy was administered due to the histopathological aggressive features of the resected pituitary tumor and growth of the residual pituitary tumor on follow-up. Although the pituitary tumor shrank after radiotherapy, there was development of multiple new intracranial extra-axial lesions, including meningiomata. Resection of a rapidly growing extra-axial tumor in the parietal convexity region was performed. Given the similar histopathological features of the convexity tumor with the prior pituitary specimen, the diagnosis of pituitary carcinoma was established. A subsequent MRI scan showed metastatic deposits along the spine. The patient's condition deteriorated and she died shortly after the last surgery. CONCLUSIONS To the best of our knowledge, there is no prior report of pituitary carcinoma in a patient with CS in the literature. Pituitary carcinomas frequently spread within the craniospinal axis, in addition to hematogenous dissemination. Given the high risks of developing malignant tumors in patients with CS, multidisciplinary management including diagnostic imaging and close surveillance are of paramount importance in patient management.