Austin McHenry

Folate receptor alpha ( FRα / FOLR1 ) and HER2 immunohistochemical staining in high‐grade endometrial carcinoma with aberrant p53 expression

Aims Mirvetuximab soravtansine is an anti‐FOLR1 (folate receptor 1/alpha) antibody–drug conjugate with a companion diagnostic immunohistochemical (IHC) biomarker for platinum‐resistant ovarian, fallopian tube and primary peritoneal carcinoma. Its effectiveness has sparked interest in FOLR1 expression in endometrial carcinoma. We evaluate the relationship of FOLR1 and HER2‐IHC expression in high‐grade p53‐aberrantly expressed endometrial carcinomas, as overexpression of both is associated with high‐grade histologic features and aggressiveness. Methods and results Carcinomas were scored for HER2‐IHC by both gastric and endometrial serous criteria and FOLR1‐IHC by Ventana package insert on tissue microarray cores. Intratumoral heterogeneity was quantified for HER2 and FOLR1 expression across multiple cores from the same tumour. A total of 291 cores (226 endometrial serous, 47 high‐grade endometrioid and 18 high‐grade Müllerian carcinoma, nos) were collected from 66 cases (discrete accession dates) from 62 patients. When stratified by two‐category HER2‐IHC status (0/1+ vs. 2+/3+, either criteria), significantly more HER2 2+/3+ cores (16/133, 12%) were FOLR1‐positive by a ≥75% cut‐off than HER2 0/1+ specimens (8/158, 5%, P  = 0.031). Results were similar by a ≥25% cut‐off (49/133, 37% vs. 38/158, 24%; P  = 0.018). More cases with high HER2‐IHC heterogeneity (2–3‐pt difference) also demonstrated FOLR1‐IHC heterogeneity (≥50% score difference between cores from the same case) than cases with no or low (1‐pt) HER2‐IHC heterogeneity, though most cases did not show high HER2 or FOLR1 intratumoral heterogeneity (16.7%–18.2% 2–3‐pt difference and 12.1% ≥50% score difference). Conclusions A positive correlation between HER2 and FOLR1 overexpression may be seen in high‐grade endometrial carcinomas with aberrant p53 expression, which may extend to intratumoral heterogeneity of biomarker expression.

Comparison of Endometrial Serous and Gastric HER2 Immunohistochemistry Scoring Schemes in Endometrial Carcinomas With Aberrant p53 Expression: Reproducibility and In Situ Hybridization Correlation

In 2023, the College of American Pathologists (CAP) supported histotype-specific scoring for HER2 testing in endometrial serous carcinoma based on enrollment criteria for trastuzumab eligibility in the NCT01367002 clinical trial. However, in 2024, the DESTINY-PanTumor02 trial showed the benefit of trastuzumab-deruxtecan in patients with HER2-IHC 2+ and 3+ tumors using CAP gastric scoring, resulting in confusion about how these criteria relate. We compare the results of these scoring schemes by interobserver agreement and correlation with HER2/Chromosome 17 dual in situ hybridization (DISH). Six observers scored 44 HER2-IHC stained p53-abnormal endometrial carcinoma specimens in tissue microarray (TMA) format by endometrial serous (NCT01367002) and gastric systems. Interobserver agreement for HER2 scores (0, 1+, 2+, and 3+) was 81.5% (kappa=0.75) for endometrial serous and 84.6% (kappa=0.79) for gastric scoring. Eight specimens showed discordant HER2 endometrial serous and gastric scores: 4 endometrial serous 1+/gastric 0 and 4 endometrial serous 2+/gastric 3+. HER2-IHC-DISH discordance occurred in 4 specimens by gastric criteria (IHC 3+/DISH negative) and 1 specimen by endometrial serous criteria (IHC 3+/DISH negative). Endometrial serous and gastric HER2-IHC scoring schemes show similar interobserver agreement. In instances of minimal, faint HER2 staining, the endometrial serous score may be 1+ when the gastric score is 0. In instances of limited, strong HER2 staining, the endometrial serous score may be 2+ when the gastric score is 3+. The endometrial serous scheme appears more concordant with DISH results than the gastric scheme, which shows non-infrequent IHC 3+ cases without HER2-DISH amplification. We emphasize recognition of HER2-IHC therapy-specific scoring in endometrial carcinomas, as these scoring systems are similar but not identical.

Molecular classification of metastatic and recurrent endometrial endometrioid carcinoma: prognostic relevance among low‐ and high‐stage tumours

AimsMolecular classification according to The Cancer Genome Atlas (TCGA) improves endometrial endometrioid carcinoma (EEC) prognostication and has specific treatment implications; however, original data were skewed towards low‐grade and low‐stage tumours. Herein, we molecularly classify EECs metastatic at the time of diagnosis or with subsequently documented recurrent/metastatic disease to examine correlation with clinical outcomes.MethodsTCGA categories include POLE‐mutated, microsatellite instability (MSI), p53 abnormal (p53 abnl) and no specific molecular profile (NSMP). POLE targeted sequencing at exons 9, 11, 13 and 14 and immunohistochemistry (IHC) for PMS2, MSH6 and p53 were performed to establish molecular classification.ResultsThe distribution in our cohort of 141 EECs was similar to that generally reported in EEC, with nine POLE‐mutated (6%), 45 MSI (32%), 16 p53 abnl (11%) and 71 NSMP (50%), with similar distributions between low‐ and high‐stage cohorts. We demonstrate that when stratified by molecular subtype, disease‐specific survival from the time of high‐stage (stages III–IV) presentation or time of recurrence in low‐stage (stages I–II) disease among metastatic and/or recurrent EEC is strongly associated with TCGA classification (high‐stage P = 0.02, low‐stage P = 0.017). Discordant molecular classification between primary and metastatic/recurrent tumours occurred in four of 105 (3.8%) patients, two related to PMS2/MSH6 IHC and two related to p53 IHC.ConclusionsWe demonstrate that molecular classification is prognostically relevant not only at the time of diagnosis, but also at the time of recurrence and in the metastatic setting. Rare subclonal alterations occur and suggest a role for confirming TCGA classification in recurrent/metastatic tumours.

Prospective Fumarate Hydratase Tumor Predisposition Syndrome Screening in Patients With Uterine Smooth Muscle Tumors

Fumarate hydratase tumor predisposition syndrome (FHTPS) is caused by germline fumarate hydratase (FH) pathogenic variants (PVs). Most women with FHTPS develop FH-deficient (FHD) uterine leiomyomas (ULs), which arise 10 to 15 years earlier than aggressive FHD–renal cell carcinoma. We evaluate a previously proposed FHTPS screening strategy for women with ULs. This 5-year, prospective and retrospective study performed FH and later S-(2-succino) cysteine immunohistochemistry (IHC) on all uterine smooth muscle (USM) tumors in patients 40 (later ≤30) years or younger and on all USM tumors with suggestive FHD morphology regardless of age. Patients with FHD tumors by IHC were referred to genetic counseling. Of 840 USM tumors, 112 FHD-tumors by IHC (13%) were identified, all with suggestive FHD-morphology; 44 patients (39%) underwent germline testing, and 15 harbored germline FH PVs (34.1% of germline tested, 13.4% of all FHD-tumors). While FHD tumors were seen across a wide age range (24 to 73 y), those with germline FH PVs were significantly younger (median 33 vs 44 years wild-type, P = 0.0032). Few (12.5%) patients ≥40 and no patients ≥50 had a germline FH PV, whereas a majority (60%) of patients <40 (86% of those <30) had a germline FH PV. We demonstrate that previously proposed resource-conscious screening involving morphology and IHC is effective for identifying women with FHTPS. We provide prospective data confirming patients presenting with FHD-ULs over age 50 are unlikely to harbor germline FH PVs and argue that for germline testing without consideration of other factors, a threshold of younger than 50 years may be appropriate.