Cytoplasmic Pattern p53 Immunoexpression in Pelvic and Endometrial Carcinomas With TP53 Mutation Involving Nuclear Localization Domains: An Uncommon But Potential Diagnostic Pitfall With Clinical Implications

Abnormal p53 Immunohistochemical Patterns Are Associated with Regional Lymph Node Metastasis in Oral Cavity Squamous Cell Carcinoma at Time of Surgery

Most (60%-80%) of the oral cavity invasive squamous cell carcinoma (OSCC) demonstrate molecular alterations in TP53. The presence of TP53 mutations in multiple organ systems has been associated with a more aggressive clinical course. This study aimed to classify OSCC into p53 wild-type OSCC and p53-abnormal OSCC using p53 immunohistochemistry and to determine if abnormal p53 status correlates with a higher risk of lymph node metastasis at the time of surgery. A total of 101 patients with OSCC resection and cervical lymph node dissection were identified. p53 immunohistochemistry was performed for all cases and scored into p53 wild-type (p53-HPV: midepithelial/basal sparing, markedly reduced [null-like]/basal sparing; p53-conventional: scattered basal, patchy basal/parabasal) and p53-abnormal (overexpression basal/parabasal only, overexpression basal/parabasal to diffuse, null, and cytoplasmic) patterns. p16 immunohistochemistry and high-risk HPV RNA in situ hybridization were used to confirm the HPV status in cases showing midepithelial/basal sparing or markedly reduced (null-like)/basal sparing pattern. Logistic regression analysis was performed to investigate the association of p53 status, tumor size, depth of invasion, and pT stage against lymph node status. We identified 22 cases with p53 wild-type patterns (16 p53-conventional, 6 p53-HPV) and 79 cases with p53-abnormal patterns. Two of 22 p53 wild-type cases had positive lymph nodes (1 p53-conventional, 1 p53-HPV), whereas 40 of 79 p53-abnormal cases had positive lymph nodes (P < .001). Multivariate analysis showed that p53-abnormal pattern was an independent risk factor associated with positive node(s) with an odds ratio of 8.12 (95% CI, 2.10-53.78; P = .008). p53-Abnormal OSCCs were significantly more likely to be associated with positive lymph node status than p53 wild-type OSCCs at the time of surgery. Further investigation with long-term follow-up is required to determine its clinical application before surgery planning.

New clinicopathological concept of endometrial carcinoma with integration of histological features and molecular profiles

The dual-stratified pathway of endometrial carcinomas (ECs) has long been dominant. However, in 2013, The Cancer Genome Atlas (TCGA) defined four EC subgroups with distinctive prognoses. Inspired by TCGA, in 2018, the Proactive Molecular Risk Classifier for Endometrial Cancer (ProMisE) provided four pragmatic molecular classifiers to apply surrogate immunohistochemical markers to TCGA subgroup categorization. These trends prompted the revision of 2020 WHO Classification of Female Genital Tumors, 5th edition (2020 WHO classification), in which four molecular subtypes are recognized: POLE-ultramutated; mismatch repair-deficient; p53-mutant; and no specific molecular profile. In the 2020 WHO classification, the diagnostic algorithm is characterized by prioritizing POLEmut over other molecular abnormalities. Following the 2020 WHO classification, Federation of International Gynecology and Obstetrics (FIGO) proposed a new staging system in 2023. The updated system focuses on diagnostic parameters, such as histological type and grade, lymphovascular space invasion, and molecular alterations. These new histomolecular diagnostic concepts of ECs are being accordingly introduced into the routine pathology practice. For the first time, the 2020 WHO classification includes mesonephric-like adenocarcinoma (MLA) as a novel histological entity, mimicking the conventional mesonephric adenocarcinoma, but is considered of Müllerian ductal origin.

p53 protein expression patterns associated with TP53 mutations in breast carcinoma

PURPOSE

The importance of a TP53 mutation has been demonstrated in several tumor types, including breast cancer (BC). However, the accuracy of p53 protein expression as a predictor of gene mutation has not been well studied in BC. Therefore, we evaluated p53 protein expression associated with TP53 mutations in breast cancers from 64 patients.

METHODS

TP53 mutation was examined using next-generation sequencing (NGS). p53 protein expression was examined using immunohistochemistry (IHC).

RESULTS

Among the 64 BCs, 55% demonstrated abnormal expression patterns including 27% overexpression, 22% null, 6% equivocal with 45% having a wild-type pattern. A TP53 mutation was present in 53% (34/64) of tumors including 30% (19/64) demonstrating a missense mutation, 11% (7/64) with a frameshift mutation, 11% (7/64) with a nonsense mutation, and 3% (1/64) with a splice site mutation. Abnormal expression of p53 protein was present in 33 of 34 (97%) tumors carrying a TP53 mutation; conversely, a wild-type pattern was present in 28 of 30 (93%) tumors without a detectable mutation (p < 0.0001). The majority of BCs with a p53 IHC overexpression pattern (15/17, 88%) contained a missense TP53 mutation; while the majority of BCs with a null pattern (12/14, 86%) contained a truncating mutation (p < 0.0001). The BCs with a null pattern are associated with a high Nottingham histological grade and a triple-negative phenotype when compared to those demonstrating overexpression (p < 0.05).

CONCLUSION

These findings suggest that p53 IHC can be a potential surrogate for TP53 mutations in BC. Different p53 expression patterns may correlate with specific TP53 genetic mutations in BC.

Prospective Clinical Prognostication of Endometrial Carcinomas Based on Next-Generation Sequencing and Immunohistochemistry-Real-World Implementation and Results at a Tertiary Care Center

Based on findings from The Cancer Genome Atlas and the Proactive Molecular Risk Classifier for Endometrial Cancer algorithm, endometrial carcinoma can now be stratified into 4 prognostically distinct subgroups based on molecular alterations and immunohistochemical (IHC) aberrations. In this study, we describe the de novo adoption and clinical reporting of prognostic subgroup classification based on next-generation sequencing (NGS) and IHC analyses of all endometrial carcinoma resections at a single institution, framed by the Exploration, Preparation, Implementation, and Sustainment model. Results from the first 13 months show 188 tumors underwent analysis by a combination of IHC and a medium-sized (56 analyzed genes) NGS-based assay. All cases were assigned as either POLE ( POLE -mutated) (5.3%), mismatch repair deficient (27.7%), no specific molecular profile (45.7%), or p53 abnormal (21.3%) inclusive of multiple-classifier cases. NGS-based analysis revealed additional distinctions among the subgroups, including reduced levels of PI3K pathway activation in the p53 abnormal subgroup, an increased rate of CTNNB1 activating mutation in the no specific molecular profile subgroup, and lower TP53 mutation variant allele frequencies in POLE and mismatch repair deficient subgroups compared with the p53 abnormal subgroup. Overall, we describe the testing protocol, reporting, and results of a combination of NGS and IHC to prospectively prognosticate endometrial carcinomas at a single tertiary care center.

The pattern-based interpretation of p53 immunohistochemical expression as a surrogate marker for TP53 mutations in colorectal cancer

Mutations in the TP53 gene, most commonly observed in colorectal cancer (CRC), play an essential role in colorectal carcinogenesis. Although p53 immunohistochemical (IHC) expression patterns have been argued to serve as an excellent surrogate marker for TP53 mutations, its performance has not been confirmed in CRC. We aimed to determine whether p53 IHC expression patterns accurately predict TP53 mutation status as examined by next-generation sequencing (NGS). We performed p53 IHC and sequencing of TP53 by NGS in 92 CRC cases with a microsatellite stable phenotype to investigate the correlation between TP53 mutation status and p53 IHC expression. The concordance between p53 IHC and TP53 mutation was 84/92 (91.3%) overall. However, 6 mutant cases were found in 39 cases with a wild-type IHC pattern. Additionally, there were two discordant cases in which an abnormal p53 IHC pattern (overexpression or cytoplasmic pattern) was found, while NGS detected wild-type p53. Therefore, the optimized p53 IHC performs well and serves as a surrogate test for TP53 mutation in CRC cases. Furthermore, it demonstrates excellent reproducibility between two independent experienced pathologists and may have novel clinical utility for molecular classification algorithms in CRC. We suggest that the four-tier classification of p53 IHC patterns is helpful to evaluate molecular colorectal carcinogenesis.

Immunohistochemical and molecular pattern of p53 in epithelial ovarian cancers negative for germline BRCA1/2 variants

Epithelial ovarian cancers (EOC) associated with germline or somatic BRCA pathogenetic variants have a significantly higher rate of TP53aberrations. The majority of TP53 mutations are detectable by immunohistochemistry and several studies demonstrated that an abnormal p53 pattern characterized high-grade EOCs. An abnormal p53 immunohistochemical staining in fallopian tube (serous tubal intraepithelial carcinoma (STIC) and "p53 signature" is considered as a precancerous lesion of high-grade EOCs and it is often found in fallopian tube tissues of BRCA germline mutated patients suggesting that STIC is an early lesion and the TP53 mutation is an early driver event of BRCA mutated high-grade EOCs. No relevant data are present in literature about the involvement of p53 abnormal pattern in EOC carcinogenesis of patients negative for germline BRCA variants. We describe TP53 mutation results in relationship to the immunohistochemical pattern of p53 expression in a series of EOCs negative for BRCA1 and BRCA2 germline mutations. In addition, we also investigated STIC presence and "p53 signature" in fallopian tube sampling of these EOCs. Our results demonstrate that TP53 alterations are frequent and early events in sporadic EOCs including also low-grade carcinomas. Also in this series, STIC is associated with an abnormal p53 pattern in fallopian tubes of high-grade EOCs. In summary, TP53 aberrations are the most frequent and early molecular events in EOC carcinogenesis independently from BRCA mutation status.

Implication of cytoplasmic p53 expression in pulmonary neuroendocrine carcinoma using next-generation sequencing analysis

AIMS

Cytoplasmic p53 expression indicates a high frequency of TP53 abnormalities in gynaecological carcinoma. However, the implication of this expression in pulmonary neuroendocrine carcinoma (NEC) remains unclear. Thus, our study aimed to fill this research gap.

METHODS AND RESULTS

Immunohistochemistry (IHC) of p53 was performed on 146 cases of resected small-cell lung carcinoma and large-cell NEC, and next-generation sequencing was conducted on cases showing cytoplasmic and wild-type p53 expression. IHC revealed overexpression in 57% of the cases (n = 83), complete absence in 31% (n = 45), cytoplasmic expression in 8% (n = 12) and wild-type expression in 4% (n = 6) of the cases. TP53 mutations were identified in nine of the 13 cases with available genetic analysis. The TP53 mutation rates in cases with cytoplasmic and wild-type p53 expression were 88% (seven of eight) and 40% (two of five), respectively. All seven cases showing cytoplasmic expression with TP53 mutations harboured loss-of-function type mutations: four had mutations in the DNA-binding domain, two in the nuclear localisation domain and one in the tetramerisation domain. Clinically, cases with cytoplasmic p53 expression had a poor prognosis similar to that in cases with p53 overexpression or complete absence.

CONCLUSIONS

Cytoplasmic p53 expression in patients with pulmonary NEC suggests a high TP53 mutation rate, which is associated with a poor prognosis similar to that in patients with p53 overexpression or complete absence. This cytoplasmic expression should not be misidentified as a wild-type expression. This is the first report, to our knowledge, that demonstrates the implication of cytoplasmic p53 expression in pulmonary NEC.

Comparative analysis of EZH2, p16 and p53 expression in uterine carcinosarcomas

Introduction: The role of p16 and p53 immunohistochemistry in the diagnosis of rare and aggressive uterine carcinosarcoma (UCS) has been well established. However, enhancer of zeste homolog 2 (EZH2), a histone methyltransferase and a member of the polycomb group family is a relatively new biomarker, with limited published data on its significance in this tumor type. The goal of this study was to examine EZH2 expression in UCS and its components, in correlation with morphological features, and p16 and p53 staining patterns. Methods: Twenty-eight UCSs were included in the study. EZH2, p16 and p53 immunoreactivity were assessed independently by two pathologists in both tumor components (epithelial and mesenchymal). EZH2 and p16 immunostains were scored semiquantitatively: based on the percentage and intensity of tumor cell staining a binary staining index ("high- or low-expressing") was calculated. The p53 staining pattern was evaluated as wild-type or aberrant (diffuse nuclear, null, or cytoplasmic expression). Statistical tests were used to evaluate the correlation between staining patterns for all three markers and the different tumor components and histotypes. Results: High EZH2 and p16 expression and aberrant p53 patterns were present in 89.3% 78.6% and 85.7% of the epithelial component and in 78.6%, 62.5% and 82.1% of the mesenchymal component, respectively. Differences among these expression rates were not found to be significant (p > 0.05). Regarding the epithelial component, aberrant p53 pattern was found to be significantly (p = 0.0474) more frequent in the serous (100%) than in endometrioid (66.6%) histotypes. Within the mesenchymal component, p53 null expression pattern occurred significantly (p = 0.0257) more frequently in heterologous sarcoma components (71.4%) compared to the homologous histotype (18.8%). Conclusion: In conclusion, EZH2, p16 and p53 seem to play a universal role in the pathogenesis of UCS; however, a distinctive pattern of p53 expression appears to exist between the serous and endometrioid carcinoma components and also between the homologous and heterologous sarcoma components.

Utilization of p53 and p16 Immunohistochemistry in the Classification of Human Papillomavirus-Associated, p53 Wild-Type, and p53 Abnormal Oral Epithelial Dysplasia

p53 immunohistochemistry (IHC) has recently been shown to be a clinically useful marker for predicting risk of progression to invasive squamous cell carcinoma in oral epithelial dysplasia (OED). The literature supports the use of p53 IHC as a marker to identify TP53 mutation in in situ and invasive vulvar lesions and as a surrogate marker for high-risk human papillomavirus (HPV) infection, but there is little documentation for similar use in OED. The purpose of this study was to determine whether p53 IHC is a reliable surrogate marker for detecting both TP53 mutation and high-risk HPV infection in OED. We studied 57 cases of OED (11 mild, 18 moderate, and 28 severe), and all were stained for p16 and p53 IHC. High-risk HPV RNA in situ hybridization (ISH) was performed in selected cases (all p16-positive cases and all OED showing abundant apoptotic cells and karyorrhectic cells; N = 27). Targeted next-generation sequencing (NGS) was performed in 33 p16-negative cases and all high-risk HPV RNA ISH-negative cases (N = 36). We identified 21 cases with p53 basal sparing patterns (mid-epithelial and markedly reduced [null-like]), 14 cases with p53 wild-type patterns (scattered basal and patchy basal/parabasal), and 22 cases with p53 abnormal patterns (18 overexpression, 3 null, and 1 novel cytoplasmic pattern). Among cases with p53 basal sparing patterns, 20 were positive for p16 (20/21, 95%), and all were positive for high-risk HPV RNA ISH (21/21, 100%). The 36 sequenced cases had IHC patterns concordant with TP53 mutation status in 92% (33/36) of lesions. This study demonstrates that p53 IHC expression patterns are sensitive and specific for detection of both high-risk HPV infection and TP53 mutation. Coupled with selective p16 IHC testing, this IHC panel can accurately subclassify OED into HPV-associated, p53 wild-type (conventional), and p53 abnormal OED.

Correlative Assessment of p53 Immunostaining Patterns and TP53 Mutation Status by Next-Generation Sequencing in High-Grade Endometrial Carcinomas

TP53 mutations are frequently identified in the copy number-high molecular subgroup of endometrial carcinomas (ECs). P53 immunohistochemistry (IHC) is a widely used surrogate marker reflecting the mutational status of TP53 , and recent reports have shown ~95% concordance between the two methods in ECs. While these results are promising, studies evaluating the correlation between different p53 IHC staining patterns and comprehensive next-generation sequencing results are still limited. We compared the p53 IHC staining patterns, scored as wild-type, diffuse nuclear overexpression, null/complete absence, and cytoplasmic, to next-generation sequencing results reported by FoundationOneCDx in 43 high-grade ECs: 20 serous ECs, 9 mixed ECs with a serous component, 4 carcinosarcomas with a serous component, and 10 grade 3 endometrioid ECs. The concordance of p53 IHC and TP53 mutation status was 100% (43/43) overall, including 100% (33/33) concordance in tumors with a serous component and 100% (10/10) in endometrioid ECs. Among the 35 tumors with aberrant p53 expression the most commonly observed pattern was diffuse nuclear overexpression seen in 69% (24/35), followed by cytoplasmic staining in 17% (6/35), and complete absence of staining (null) in 14% (5/35) of tumors. Of the 6 tumors with cytoplasmic staining, 4 corresponded to missense mutations within the DNA binding domain (V157F in 2 tumors, and S127P and R280S, in 2 tumor each), while 2 corresponded to nonsense mutations in the tetramerization domain (p.E339*). Our results further support that p53 IHC can serve as an accurate predictor of TP53 alterations in ECs to aid the molecular-based tumor classification and the distinction between tumor histotypes, both of which play an important role in the assessment of clinical prognosis and therapeutic decision making. In addition, our data suggest, that the type and position of TP53 mutation may not directly correlate with the observed p53 IHC pattern in all tumors, and that there may be alternative mechanisms for cytoplasmic localization (other than mutations involving the nuclear localization domain), possibly due to conformational changes or posttranslational modifications of the aberrant p53 protein.

Distinct histological and clinical features associated with pure uterine serous carcinoma: A single institution experience

AIM

To ascertain the clinicopathological features, survival, and prognostic factors of pure uterine serous carcinoma (pUSC) and compare its clinicopathological characteristics with those of serous-like grade-3 endometrioid endometrial carcinoma (G3-EEC).

METHOD

Consecutive patients with pUSC and p53 abnormal (p53abn) G3-EEC were retrospectively selected between 2014 and 2022. Histological and immunohistochemical features were reviewed, clinical information was collected, and survival analyses were performed.

RESULTS

Eighty-five pUSC patients (mean age: 61.6 years) were included. Histologically, pUSC showed a predominantly glandular growth pattern (80.0 %) with high-grade nuclear atypia and obvious nucleoli and 53 cases showed admixtures of architectural patterns. The p53 aberrant expression rate was 98.8 %. 41.5 %, 53.7 %, and 67.5 % of cases were classified as negative for ER, PR, and WT1, respectively. Six (12.3 %) of 49 cases had a HER2 score of 3+ by immunohistochemistry (IHC). The overall survival and progression-free survival rates were 72.9 % and 63.5 %, respectively. Advanced stage, no adjuvant therapy, and lymph node metastasis were independent risk factors for poor survival in pUSC. Twenty-five p53abn G3-EEC patients were assessed. Women with p53abn G3-EEC were on average, younger than those with pUSC (53.4 vs. 61.6 years, P < 0.001). Papillary structures were observed more commonly in pUSC (16 % vs. 36.5 %, P = 0.042). Positive PR expression was significantly associated with p53abn G3-EEC (P = 0.009). Survival did not differ significantly between the subgroups in univariate and multivariate analyses.

CONCLUSION

In this contemporary series, we affirm the suboptimal prognosis associated with pUSC, and that the survival associated with pUSC and p53abn G3-EEC are not significantly different. pUSC and p53abn G3-EEC have distinct morphological and immunohistochemical characteristics.

p53 as Exemplar Next-Generation Immunohistochemical Marker: A Molecularly Informed, Pattern-Based Approach, Methodological Considerations, and Pan-Cancer Diagnostic Applications

This review is based on a webinar I presented for the International Society for Immunohistochemistry and Molecular Morphology (ISIMM) in February 2022. It is intended that all ISIMM webinars will ultimately be published in AIMM as review articles. This work is also dedicated to Clive Taylor, who has deeply impacted my career. It presents a molecularly informed, pattern-based approach to p53 immunohistochemistry interpretation, methodological considerations (ie, antibody selection, optimization, validation, controls, and external quality assessment), and pan-cancer diagnostic applications, including those drawn from gastrointestinal, genitourinary, gynecological, neuroendocrine, hematologic, and neuropathology. It intends to prove the thesis statement that p53 is an exemplar next-generation immunohistochemical marker "born" ahead of its time.

p53 and ovarian carcinoma survival: an Ovarian Tumor Tissue Analysis consortium study

Our objective was to test whether p53 expression status is associated with survival for women diagnosed with the most common ovarian carcinoma histotypes (high-grade serous carcinoma [HGSC], endometrioid carcinoma [EC], and clear cell carcinoma [CCC]) using a large multi-institutional cohort from the Ovarian Tumor Tissue Analysis (OTTA) consortium. p53 expression was assessed on 6,678 cases represented on tissue microarrays from 25 participating OTTA study sites using a previously validated immunohistochemical (IHC) assay as a surrogate for the presence and functional effect of TP53 mutations. Three abnormal expression patterns (overexpression, complete absence, and cytoplasmic) and the normal (wild type) pattern were recorded. Survival analyses were performed by histotype. The frequency of abnormal p53 expression was 93.4% (4,630/4,957) in HGSC compared to 11.9% (116/973) in EC and 11.5% (86/748) in CCC. In HGSC, there were no differences in overall survival across the abnormal p53 expression patterns. However, in EC and CCC, abnormal p53 expression was associated with an increased risk of death for women diagnosed with EC in multivariate analysis compared to normal p53 as the reference (hazard ratio [HR] = 2.18, 95% confidence interval [CI] 1.36-3.47, p = 0.0011) and with CCC (HR = 1.57, 95% CI 1.11-2.22, p = 0.012). Abnormal p53 was also associated with shorter overall survival in The International Federation of Gynecology and Obstetrics stage I/II EC and CCC. Our study provides further evidence that functional groups of TP53 mutations assessed by abnormal surrogate p53 IHC patterns are not associated with survival in HGSC. In contrast, we validate that abnormal p53 IHC is a strong independent prognostic marker for EC and demonstrate for the first time an independent prognostic association of abnormal p53 IHC with overall survival in patients with CCC.

Mass Spectrometry Proteomic Analysis of Four p53 Patterns in Differentiated Vulvar Intraepithelial Neoplasia

OBJECTIVE

The histopathologic diagnostic criteria of differentiated vulvar intraepithelial neoplasia (dVIN), the precursor of human papillomavirus-independent squamous cell carcinoma, are basal atypia, a negative or non-block-positive p16, and a supportive p53 immunohistochemistry (IHC). Several different patterns of supportive p53 IHC have been described. This study aims to determine the relationship between p53 IHC patterns and mass spectrometry analysis of cellular proteins in dVIN.

METHODS

Four patterns of p53 IHC were studied: overexpression, cytoplasmic, wild type, and intermediate expression between wild type and overexpression. For each pattern, tissue samples of 4 examples were subjected to mass spectrometry.

RESULTS

The protein profile within each p53 IHC pattern shared common features. Each of the 4 p53 patterns had a distinguishable protein profile when compared with the other 3 patterns.

CONCLUSIONS

The distinguishable protein profiles in different p53 IHC patterns suggest diverse mechanisms of TP53 dysfunction. Subtyping dVIN by p53 IHC is worthy of further study because varied protein expression profiles may translate into different clinical behavior.

Consensus based recommendations for the diagnosis of serous tubal intraepithelial carcinoma: an international Delphi study

AIM

Reliably diagnosing or safely excluding serous tubal intraepithelial carcinoma (STIC), a precursor lesion of tubo-ovarian high-grade serous carcinoma (HGSC), is crucial for individual patient care, for better understanding the oncogenesis of HGSC, and for safely investigating novel strategies to prevent tubo-ovarian carcinoma. To optimize STIC diagnosis and increase its reproducibility, we set up a three-round Delphi study.

METHODS AND RESULTS

In round 1, an international expert panel of 34 gynecologic pathologists, from 11 countries, was assembled to provide input regarding STIC diagnosis, which was used to develop a set of statements. In round 2, the panel rated their level of agreement with those statements on a 9-point Likert scale. In round 3, statements without previous consensus were rated again by the panel while anonymously disclosing the responses of the other panel members. Finally, each expert was asked to approve or disapprove the complete set of consensus statements. The panel indicated their level of agreement with 64 statements. A total of 27 statements (42%) reached consensus after three rounds. These statements reflect the entire diagnostic work-up for pathologists, regarding processing and macroscopy (three statements); microscopy (eight statements); immunohistochemistry (nine statements); interpretation and reporting (four statements); and miscellaneous (three statements). The final set of consensus statements was approved by 85%.

CONCLUSION

This study provides an overview of current clinical practice regarding STIC diagnosis amongst expert gynecopathologists. The experts' consensus statements form the basis for a set of recommendations, which may help towards more consistent STIC diagnosis.

Spatial genomic diversity associated with APOBEC mutagenesis in squamous cell carcinoma arising from ovarian teratoma

Although the gross and microscopic features of squamous cell carcinoma arising from ovarian mature cystic teratoma (MCT-SCC) vary from case to case, the spatial spreading of genomic alterations within the tumor remains unclear. To clarify the spatial genomic diversity in MCT-SCCs, we performed whole-exome sequencing by collecting 16 samples from histologically different parts of two MCT-SCCs. Both cases showed histological diversity within the tumors (case 1: nonkeratinizing and keratinizing SCC and case 2: nonkeratinizing SCC and anaplastic carcinoma) and had different somatic mutation profiles by histological findings. Mutation signature analysis revealed a significantly enriched apolipoprotein B mRNA editing enzyme catalytic subunit (APOBEC) signature at all sites. Intriguingly, the spread of genomic alterations within the tumor and the clonal evolution patterns from nonmalignant epithelium to cancer sites differed between cases. TP53 mutation and copy number alterations were widespread at all sites, including the nonmalignant epithelium, in case 1. Keratinizing and nonkeratinizing SCCs were differentiated by the occurrence of unique somatic mutations from a common ancestral clone. In contrast, the nonmalignant epithelium showed almost no somatic mutations in case 2. TP53 mutation and the copy number alteration similarities were observed only in nonkeratinizing SCC samples. Nonkeratinizing SCC and anaplastic carcinoma shared almost no somatic mutations, suggesting that each locally and independently arose in the MCT. We demonstrated that two MCT-SCCs with different histologic findings were highly heterogeneous tumors with clearly different clones associated with APOBEC-mediated mutagenesis, suggesting the importance of evaluating intratumor histological and genetic heterogeneity among multiple sites of MCT-SCC.

Cytohistologic immunohistochemical correlation of epithelial tubo-ovarian neoplasms: Can cell blocks substitute for tissue?

BACKGROUND

Cytologic specimens often represent the initial diagnostic material for tubo-ovarian neoplasms resulting from therapeutic paracentesis for patients presenting with high-volume ascites. However, subtyping and immunohistochemical (IHC) characterization, which have implications in preoperative management and downstream ancillary testing, are not routinely performed in many institutions. This study aims to perform cytohistologic correlation of commonly used IHC stains to establish their reliability in peritoneal fluids/washing specimens.

METHODS

A retrospective search of the laboratory information systems was performed to identify peritoneal fluid/washing specimens involved by borderline or malignant epithelial tubo-ovarian neoplasms and concurrent/subsequent surgical resection specimens. Cell blocks and tissue were stained for PAX8, WT-1, p53, p16, Napsin-A, estrogen receptor, and progesterone receptor, and staining between cytological and surgical specimens was compared.

RESULTS

A total of 56 case pairs were included, with the following final diagnoses on histological examination: 37 high-grade serous carcinomas, eight clear cell carcinomas, one endometrioid adenocarcinoma, two low-grade serous carcinomas, and eight serous borderline tumors. There was perfect cytohistologic correlation for PAX8 (Lin's concordance correlation coefficient [LINCCC] = 1.00) and WT-1 (LINCCC = 1.00), substantial/good correlation for p53 (LINCCC = 0.96), p16 (LINCCC = 0.93), napsin-A (LINCCC = 0.91) and ER (LINCCC = 0.77), and moderate correlation for PR (LINCCC = 0.54).

CONCLUSIONS

Immunohistochemical correlation between peritoneal fluid and surgical resection specimens for tubo-ovarian neoplasms is high. Common subtypes of tubo-ovarian carcinomas can be reliably distinguished on fluids using IHC.

Loss of H3K27 trimethylation in a distinct group of de-differentiated chordoma of the skull base

De-differentiated chordoma is defined as a high-grade sarcoma lacking notochordal differentiation, which arises in association with conventional chordoma. The mechanism underlying de-differentiation remains unclear. We immunohistochemically investigated trimethylation at lysine 27 of histone 3 (H3K27me3) in nine de-differentiated chordomas. The tumours occurred at the skull base (n = 5) or the sacrum (n = 4) in four men and five women with a median age of 50 years. De-differentiation occurred de novo in four cases and at recurrence/metastasis in five cases. Five tumours retained H3K27me3, whereas four showed complete loss of H3K27me3 only in the de-differentiated component, while the conventional chordoma component retained H3K27me3. All the H3K27me3-negative tumours showed co-loss of dimethylation at H3K27 (H3K27me2), consistent with inactivation of polycomb repressive complex 2. Two genetically analysed H3K27me3-negative tumours harboured EED homozygous deletions. All four H3K27me3-negative de-differentiated chordomas affected the skull base of young or middle-aged women. Unlike dense proliferation of highly pleomorphic spindle or epithelioid cells in the H3K27me3-positive de-differentiated chordomas, all H3K27me3-negative tumours displayed swirling fascicles of relatively uniform spindle cells with alternating cellularity and perivascular accentuation, resembling malignant peripheral nerve sheath tumour (MPNST). Rhabdomyoblastic differentiation was present in one H3K27me3-negative tumour. We identified a novel group of de-differentiated chordomas in the skull base that lost H3K27me3/me2 only in the de-differentiated component, which was associated with EED homozygous deletion and MPNST-like histology. Our data suggest a distinct 'polycomb-type' de-differentiation pathway in chordoma, similar to a recently described de-differentiated chondrosarcoma with H3K27me3 loss.

Serous tubal intraepithelial carcinoma: What Do We Really Know at this Point?

Serous tubal intraepithelial carcinoma (STIC) is the earliest morphologically recognizable step in the development of invasive high-grade serous carcinoma of the fallopian tube. Lesions occurring prior to STIC within the carcinogenic sequence for the pathogenesis of invasive high-grade serous carcinoma include the p53 signature and secretory cell outgrowth (SCOUT). Variable histologic criteria have been used for diagnosing STIC, but a combination of morphology and immunohistochemistry for p53/Ki-67 improves interobserver agreement. Half of all carcinomas identified in risk-reducing salpingo-oophorectomy specimens are in the form of STIC; however, STIC also may be incidentally found on occasion in specimens from women at low or average risk of ovarian/tubal/peritoneal carcinoma. TP53 mutation is the earliest known DNA sequence alteration in STIC and almost all invasive high-grade serous carcinomas of the ovary and peritoneum. Data on the clinical behavior of STIC are limited. While the short-term follow-up in the prior literature suggests a low risk of malignant progression, a more recent meta-analysis indicates a 10-year risk of 28%. STIC probably should be best regarded as a lesion with uncertain malignant potential at present, and future molecular analysis will help classify those with higher risk of dissemination. This review article provides an update on the current knowledge of STIC and related issues.

Adult NTRK-rearranged spindle cell neoplasms of the viscera: with an emphasis on rare locations and heterologous elements

NTRK-rearranged mesenchymal neoplasms mostly affect the soft tissues of pediatric patients. Given the responsiveness to selective NTRK inhibitors, it remains critical to identify those ultra-rare cases occurring in the viscera of adults. In five females and two males aged 18-53 years, we characterized visceral mesenchymal tumors harboring TPM3-NTRK1 [uterine cervix (N = 2), pleura, prostate], LMNA-NTRK1 (lung), SQSTM1-NTRK3 (heart), and NTRK3 rearrangement with unknown fusion partner (colon/mesocolon) with RNA sequencing, FISH, RT-PCR, and immunohistochemistry. The tumors exhibited spindled to ovoid/epithelioid or pleomorphic cells, often arranged in fascicles, and were low-to-intermediate-grade and high-grade in three and four cases, respectively. Keloid-like stromal collagen and perivascular hyalinization was noted in five. Adenosarcoma-like appearances were observed in two, manifesting frond-like protrusions in one cervical tumor and phyllodes-like architecture in the prostatic tumor. Abrupt high-grade transformation into pleomorphic liposarcoma was found in another cervical tumor, while the pleural tumor contained intermixed rhabdomyoblasts. Pan-TRK immunostaining was positive in all cases. All cases expressed CD34, while five were S100-positive. CDKN2A homozygous deletion with concomitant p16 loss occurred in 4/7. Whole-exome sequencing identified TP53 mutation (c.672+2T>C, involving a splice site, with concomitant protein loss) in a cervical sarcoma, limited to its heterologous liposarcomatous component. At least moderate pan-TRK immunoreactivity was present in varying proportions of potential pathologic mimics, with BCOR-positive sarcoma (56%, 5/9), undifferentiated uterine sarcoma (50%, 3/6), and spindle cell/sclerosing rhabdomyosarcoma (33%, 2/6) being among the most frequent. This underscored the unsatisfactory specificity of pan-TRK immunohistochemistry and warranted molecular confirmation in the diagnosis of adult NTRK-rearranged visceral mesenchymal neoplasms. The current report highlights the ever-expanding clinicopathologic and genetic spectrum of this entity by describing the unprecedented cardiac and pleural locations and heterologous differentiation, as well as the second NTRK-rearranged "prostatic stromal sarcoma," while substantiating CDKN2A deletion as a frequent occurrence.

Homologous Recombination Deficiency and Ovarian Cancer Treatment Decisions: Practical Implications for Pathologists for Tumor Typing and Reporting

Clinical testing for homologous repair (HR) deficiency (HRD) in ovarian cancers has emerged as a means to tailor the use of poly(ADP-ribose)polymerase (PARP) inhibitor therapy to the patients most likely to respond. The currently available HRD tests evaluate tumor tissue for genomic evidence of impairment of the HR pathway of DNA damage repair, which, if present, renders the tumor vulnerable to PARP inhibitors in conjunction with platinum chemotherapy. Germline or somatic mutation of BRCA1/2 is a major contributor HRD. Thus, tubo-ovarian/peritoneal high-grade serous carcinoma (HGSC) is enriched by HRD. After highlighting the general concepts underlying HRD testing and PARP inhibitor therapy, this review discusses practical roles for pathologists to maximize the opportunities for eligible patients with ovarian cancer to benefit from HRD testing, chiefly by applying contemporary diagnostic criteria for ovarian cancer tumor typing and navigating through potential pitfalls of tumor types that may mimic HGSC but are unlikely to harbor HRD.

Cytoplasmic P53 Immunostaining With N-Terminus P53 Antibody And Absence Of Staining With C-Terminus P53 Antibody: A Report Of Two Pediatric Sarcomas With Distal Truncating TP53 Mutations Affecting Nuclear Localization Domain

P53 immunohistochemical staining with antibodies targeted to epitopes at or near the N-terminus are commonly used in diagnostic pathology practice as a surrogate for TP53 mutations. The abnormal staining patterns indicating TP53 mutations include nuclear overexpression, null, and the recently described cytoplasmic staining. The latter staining pattern occurs with the less common TP53 mutations affecting its nuclear localization and/or tetramerization domains that are located toward the C-terminus. Here we describe the first two cases of pediatric sarcomas with cytoplasmic staining with P53 antibody against N-terminus epitope and the absence of staining with P53 antibody against C-terminus epitope. We propose that a more precise description of P53 immunohistochemical staining patterns should include the nature of the antibody used.

Immunohistochemistry in gynecologic carcinomas: Practical update with diagnostic and clinical considerations based on the 2020 WHO classification of tumors

This review provides an update on immunohistochemistry applications-diagnostic, prognostic, and predictive-in the pathology evaluation of gynecologic carcinomas. The 5th edition of the WHO Classification of Female Genital Tumors introduced important changes in the diagnostic classification of lower genital tract, endometrial, and ovarian carcinomas, with major influence on the routine pathology practice. Lower genital tract carcinomas and their precursor lesions are now classified based on their human papillomavirus (HPV)-associated and HPV-independent pathogenesis, reflecting the clinically significant prognostic differences and impacting the therapeutic decision-making. Immunohistochemical markers have an increasing role in the pathology evaluation of endometrial carcinomas: in addition to their traditional use in the differential diagnosis and histologic subtyping, they have also been recently advocated for prognostic classification as surrogates for the TCGA (The Cancer Genome Atlas) molecular groups. New entities - mesonephric-like adenocarcinoma and gastric (gastrointestinal)-type mucinous adenocarcinoma of the endometrium - have also been added and often require immunostains for diagnostic confirmation. Ovarian carcinomas frequently show overlapping morphologic patterns and heterogeneous appearance within the same tumor, necessitating immunohistochemical work-up. Beyond diagnostic applications, there is increasing clinical demand for screening of inherited cancer syndromes, prediction of prognosis and guiding targeted therapy. Practical issues and pitfalls related to mismatch repair protein immunohistochemistry, HER2, and PD-L1 testing are also discussed.

Expanding the Immunophenotype Spectrum of SMARCA4-Deficient Non-Small Cell Lung Carcinomas: A Case Series with Neuroendocrine Markers Expression

Aims. In recent years, SMARCA4-deficient nonsmall cell lung cancer (NSCLC) has been recognized as a distinct new subtype of lung cancer, which is characterized by loss of SMARCA4 (Brahma-related gene-1 [BRG1]) protein expression. Only a limited number of SMARCA4-deficient NSCLC case series have been reported, and their clinicopathological features have not yet been fully elucidated. Our main aim was to analyze the clinical history, histology, immunohistochemistry, and molecular pathology of 5 SMARCA4-deficient NSCLC patients with poorly differentiated or undifferentiated histology and neuroendocrine markers expression. Methods and results. Five patients with complete loss of nuclear BRG1 immunostaining were identified among 53 patients of poorly differentiated/undifferentiated NSCLC. We then performed immunohistochemical staining and gene mutation analysis using a real-time polymerase chain reaction. All patients were male aged between 58 and 82 years (average 67.6 years), with smoking exposure. Histologically, the tumors had a relatively monotonous morphology and showed solid nest-like, sheet-like growth, and geographic necrosis. Thyroid transcription factor 1, cytokeratin 7, and Napsin A were all negative (5 of 5). Moreover, all tumors showed a variable expression of neuroendocrine markers, including synaptophysin, chromogranin A and CD56. Hot spot epidermal growth factor receptor/anaplastic large-cell lymphoma kinase/c-ros oncogene 1 mutations were not detected in any of the 5 tumors. Conclusions. To the best of our knowledge, this is the first study that has reported the poorly differentiated morphology with a frequent expression of neuroendocrine markers. Our results have expanded the immunophenotype spectrum of SMARCA4-deficient NSCLC. However, the clinicopathological significance of this subset of SMARCA4-deficient NSCLC should be further clarified in larger series studies.