Michaela Bártů

Uterine mesenchymal tumours represent a group of heterogeneous tumours, the classification of which is evolving, especially in the context of a broader use of molecular testing. Some entities can be diagnosed based on the combination of morphological and immunohistochemical features. In other entities, such as endometrial sarcomas with KAT6B/A::KANSL1 fusion, the correct diagnosis cannot currently be achieved without molecular testing. In this review, we focus on some of the new entities in which molecular testing plays an essential role for diagnosis, including tumours with KAT6B/A::KANSL1 fusion, tumours with MEIS1::NCOA2 fusion, and tumours with fusion involving the KDM2B gene. In addition, uterine tumours with whorling and GREB1:CTNNB1 fusion and endometrial stromal tumours with CTNNB1 mutation will be discussed. Other tumours with recurrent molecular alterations not specific to a single entity (such as tumours with PLAG1 fusion or RAD51B fusion) are also mentioned. In summary, molecular testing is a very important part of the classification of uterine mesenchymal tumours. The growing number of emerging entities helps to correctly classify tumours into clinically significant categories. However, these entities should be viewed with caution until their clinical significance is supported by robust data, and molecular findings should always be correlated with morphological features.

Folate receptor alpha (FRα) is a promising therapeutic target due to its high expression in several tumor types and its rare expression in healthy tissue. Recently, the antibody‐drug conjugate mirvetuximab soravtansine has been approved for treatment of advanced platinum‐resistant high‐grade serous carcinoma (HGSC). Immunohistochemical expression of FRα has been extensively studied in HGSC, but most studies conducted before the clinical studies targeting FRα used variable antibodies and scoring criteria, which makes comparison of older literature data with recent studies difficult. Moreover, the data regarding its expression in other types of ovarian and other female genital tract tumors are limited or absent. In our study, we focused on immunohistochemical expression in 923 tubo‐ovarian and endometrial tumors (assessed on tissue microarrays), using standardized scoring criteria and the VENTANA FOLR1 CDx assay. The results of our study showed the highest FRα expression in serous carcinomas, specifically HGSC (45% positive cases), followed by low‐grade serous carcinoma (25%), endometrial serous carcinoma (11%), and serous borderline tumor (10%). Endometrioid and clear cell ovarian carcinomas showed rare positivity (2% and 1%, respectively). All other tumors examined were negative, including mucinous ovarian tumors, sex cord‐stromal tumors, endometrial endometrioid carcinomas, undifferentiated and dedifferentiated carcinomas, and endometrial clear cell carcinomas. In conclusion, these results confirm that FRα expression in HGSC and LGSC reaches similar values compared to published data, and is present in a minority of endometrial serous carcinomas. In other ovarian and endometrial tumors examined, FRα expression is absent or rare.

Several prognostic markers, including tumor‐infiltrating lymphocytes, which have been recently identified in penile squamous cell carcinoma (pSCC), have focused mostly on T cells. The prognostic role of B cells and tertiary lymphoid structures (TLSs) has not yet been sufficiently described. We examined whole tissue sections histopathologically for TLSs and immunohistochemically for CD20 and CD138. The B‐cell immunoscore (B‐IS) divided the cohort into five categories based on the expression of these two B‐cell/plasma cell markers (CD20 and CD138, respectively). Patients with fewer TLSs had worse overall survival (OS) [hazard ratio (HR) = 2.17; 95% CI: 0.94–5; p = 0.069]. A significant association was identified between a high TLS diameter and the presence of a lymphocytic infiltrate [odds ratio (OR) = 2.2442; 95% CI: 1.1022–4.55; p = 0.0208]. Patients with low B‐IS (HR = 1.89, 95% CI: 1.18–3.03, p = 0.008), a low number of CD20 ⁺ cells in the tumor center (HR = 1.67, 95% CI: 1.04–2.7, p = 0.035), and a low number of CD20 ⁺ cells at the tumor invasion front (HR = 1.69, 95% CI: 1.06–2.78; p = 0.028) had significantly worse OS. High B‐ISs were strongly associated with a mutated p53 profile detected by immunohistochemistry (OR = 4.76, 95% CI: 1.32–25, p = 0.011), low T‐cell immunoscores (OR = 0.49; 95% CI: 0.23–1.03; p = 0.051), and brisk lymphocytic infiltration (OR = 2.0417, 95% CI: 1.01–4.76; p = 0.037). High CD20 ⁺ cell counts at the invasion front were associated with histological grade 3 disease (OR = 2.44, 95% CI 1.15–5.26, p = 0.015). An association was also observed between low B‐IS and mutations in KMT2D (OR 0.31, 95% CI: 0.07–1.21, p = 0.057) and EGFR (OR = ∞, 95% CI: 0.86–∞, p = 0.053). In conclusion, high numbers of tumor‐infiltrating B cells within TLSs represent a favorable prognostic marker in pSCC. These findings emphasize the need to identify novel microscopic prognostic markers during pathological assessment to guide early and appropriate therapeutic strategies.

Synchronous mucinous metaplasia and neoplasia of the female genital tract (SMMN-FGT) is a rare disorder defined as mucinous lesions affecting at least two sites in the female genital tract. We report a case of SMMN-FGT in a Caucasian 65-year-old patient with a right adnexal mass. The patient underwent radical surgery and histological examination showed mucinous ovarian carcinoma combined with mucinous metaplasia of the fallopian tube. The carcinomatous infiltration also affected the left ovary, peritoneum, and omentum. Molecular analysis revealed a shared STK11 mutation in both the ovarian carcinoma and tubal metaplasia, and other mutations (including KRAS) that differed between these tissues. The patient received adjuvant chemotherapy combined with bevacizumab. As there is limited experience with SMMN-FGT, standard diagnostic and treatment protocols have not yet been established. Although association with Peutz-Jeghers syndrome (PJS) was described, our patient had no clinical signs of PJS and the detected STK11 mutation was likely somatic.

Low-grade endometrial stromal sarcoma (LG-ESS) can present diagnostic challenges, due to its overlapping morphological features with other uterine mesenchymal tumors. Misdiagnosis rates remain significant, and immunohistochemical data for LG-ESS are limited to small series and inconsistent antibody panels. This study aimed to refine the IHC profile of LG-ESS by analyzing a large, molecularly confirmed series of 147 cases using a panel of 24 antibodies, including newer markers like transgelin and smoothelin. CD10 and IFITM1, key endometrial stromal markers, were expressed in 86% (92% of those extensively) and 69% (60% of those extensively) of cases, with fusion-positive tumors showing significantly higher expression. Smooth muscle markers (α-SMA, desmin, h-caldesmon, calponin, transgelin) were variably expressed, predominantly in focal or low-intensity patterns, with α-SMA reaching the highest frequency of expression (44%). However, the intensity of smooth muscle marker expression was usually very low. Smoothelin was rarely expressed. Hormone receptors were frequently positive, with PR showing a higher frequency (92% vs. 83%) and intensity than ER. Markers like S-100, HMB45, and CD117 were largely negative; all tumors were p53 wild-type, with preserved SMARCB1/SMARCA4 expression and ALK and ROS1 negativity. This work represents the largest molecularly validated IHC study on LG-ESS, providing a robust diagnostic profile for routine pathology. By addressing key diagnostic limitations and examining newer markers, our study supports a more standardized approach to diagnosing LG-ESS and underscores the value of immunohistochemical panels, particularly in fusion-negative tumors where diagnosis relies on morphological and immunohistochemical interpretation. These findings contribute critical data for improving diagnostic accuracy.

Ovarian clear cell carcinoma (OCCC) is a subtype of ovarian carcinoma characterized by unique biological features and highly malignant characteristics including low chemosensitivity. Therefore, new therapeutic targets are needed. These could include the downstream pathways of receptor tyrosine kinases, especially the human epidermal growth factor receptor 2 (HER2). Our main objective was to characterize the HER2 status using immunohistochemistry (IHC) and FISH on 118 OCCCs, also considering the novel paradigm of HER2-zero and HER2-low status. Other aims included determination of the association between HER2 status and survival, HER2 gene DNA and RNA NGS analysis, HER2 gene expression analysis, and correlation between IHC and gene expression in HER2-zero and HER2-low cases. Cases with HER2 overexpression/amplification accounted for 5.1% (6/118), with additional 3% harbouring HER2 gene mutation. The remaining 112 (94.9%) cases were HER2-negative. Of these, 75% were classified as HER2-zero and 25% as HER2-low. This percentage of HER2 aberrations is significant concerning their possible therapeutic influence. Cases from the HER2-zero group showed significantly better survival. Although this relationship lost statistical significance in multivariate analysis, the results have potential therapeutic significance. HER2 gene expression analysis showed a significant correlation with HER2 IHC status in the entire cohort (HER2-positive vs. HER2-negative), while in the cohort of only HER2-negative cases, the results did not reach statistical significance, suggesting that gene expression analysis would not be suitable to confirm the subdivision into HER2-low and HER2-zero. Our results also emphasize the need for standardized HER2 testing in OCCC to determine the best predictor of clinical response.

Expression of neuroendocrine (NE) markers in primary ovarian non-NE epithelial tumors has rarely been evaluated. The aim of our study was to evaluate the expression of the most widely used NE markers in these neoplasms and to determine any prognostic significance of NE marker expression. The cohort consisted of 551 primary ovarian tumors, including serous borderline tumors, low-grade serous carcinomas, high-grade serous carcinomas (HGSC), clear cell carcinomas, endometroid carcinomas, mucinous borderline tumors, and mucinous carcinomas. Immunohistochemical analysis was performed using antibodies against INSM1, synaptophysin, chromogranin, and CD56 on tissue microarray. Positivity for INSM1, synaptophysin, chromogranin, and CD56 was most frequently observed in mucinous tumors (48.7%, 26.0%, 41.5%, and 100%, respectively). The positivity for these NE markers was mostly restricted to nonmucinous elements distributed throughout the tumor. The mucinous borderline tumor and mucinous carcinomas groups had similar proportions of positivity (mucinous borderline tumor: 53%, mucinous carcinomas: 39%). In the other tumor types, except for HGSC, there was only focal expression (5%–10%) or negativity for NE markers. HGSC showed high CD56 expression (in 26% of cases). Survival analysis was only performed for CD56 in HGSC as this was the only group with sufficient positive cases, and it showed no prognostic significance. Except for mucinous tumors, expression of NE markers in non-NE ovarian epithelial tumors is low. CD56 expression in HGSC occurs frequently but is without diagnostic or prognostic value.

We report a case of a 49-year-old female with desmoplastic small round cell tumor of the uterus (DSRCT). Histologically, in some areas the tumor showed typical features with ample desmoplastic stroma, while in other areas the tumor cells diffusely infiltrated myometrium with only focal desmoplastic reaction. Immunohistochemically, the tumor cells showed diffuse positivity for desmin, CD56, CD57, EMA and cyclin D1. Focal positivity was present for antibodies against cytokeratin AE1/3, BerEP4, NSE, IFITM1 and CD10. The WT-1 antibody (against the N-terminus) showed cytoplasmic positivity in some tumor cells, while the nuclei were negative. P53 expression was wild-type. The Ki-67 index (MIB1 antibody) was about 55%. Other markers examined including transgelin, myogenin, synaptophysin, chromogranin, h-caldesmon, PAX8, and CD117 were all negative. NGS analysis revealed a fusion transcript of the EWSR1 and WT1 genes. DSRCT of the uterus is a rare neoplasm, as only two cases have been reported so far. However, only one of these cases was examined molecularly with a confirmation of the characteristic EWSR1-WT1 fusion. We report a second case of molecularly confirmed DSRCT of the uterus and discuss its clinical features, differential diagnosis and the significance of molecular testing.

Hepatocyte nuclear factor 1 beta (HNF1B) is a transcription factor which plays a crucial role in nephronogenesis, and its germline mutations have been associated with kidney developmental disorders. However, the effects of HNF1B somatic exonic mutations and its role in the pathogenesis of kidney tumours has not yet been elucidated. Depending on the type of the tumour HNF1B may act as a tumour suppressor or oncogene, although the exact mechanism by which HNF1B participates in the process of cancerogenesis is unknown. Using an immunohistochemical approach, and methylation and mutation analysis, we have investigated the expression, epigenetic, and genetic changes of HNF1B in 130 cases of renal tumours (121 renal cell carcinomas, 9 oncocytomas). In the subset of clear cell renal cell carcinoma (ccRCC), decreased HNF1B expression was associated with a higher tumour grade and higher T stage. The mutation analysis revealed no mutations in the analysed samples. Promoter methylation was detected in two ccRCCs and one oncocytoma. The results of our work on a limited sample set suggest that while in papillary renal cell carcinoma HNF1B functions as an oncogene, in ccRCC and chRCC it may act in a tumour suppressive fashion.