Glioblastoma, IDH-Wildtype With Epithelioid Morphology and a BCR::NTRK2 Fusion.

Glioblastoma, IDH-wildtype (GBM) is a high-grade astrocytic glioma that accounts for the majority of malignant brain tumors in adults. Within this entity, epithelioid GBM represents a histological subtype characterized by a loosely cohesive aggregate of large cells with abundant cytoplasm, and vesicular nuclei that usually harbors the BRAF V600E mutation. Molecular alterations in GBMs are frequent and play an important role in the diagnosis of this entity. Among the many genetic alterations reported, NTRK fusions are rare and account for <2% of gliomas. Furthermore, NTRK2 fusions are most seen in pediatric populations. Recent approval of the TRK inhibitor larotrectinib by the Food and Drug Administration (FDA) has brought interest in the study and recognition of NTRK fusions in multiple types of tumors. Trials that assess the response to this drug in cancers carrying NTRK fusions have yielded favorable results. We discuss a rare presentation of an adult-type GBM with epithelioid morphology and a BCR::NTRK2 gene fusion.

Metastatic Testicular Sex Cord Tumor Harboring a EWSR1::ATF1 Gene Fusion-A Case Report of a Novel Neoplasm: "Inflammatory and Nested Testicular Sex Cord Tumor".

We present a case report of a 54-year-old male with a metastatic testicular sex cord tumor harboring a EWSR1::ATF1 gene fusion. The tumor displayed a solid and nested architecture with sclerotic stroma and variable inflammatory infiltrate, and was positive for SF-1, inhibin, EMA, CD30, and WT1 expression. Further genetic analysis identified a EWSR1::ATF1 gene fusion. Overall findings were consistent with an "inflammatory and nested testicular sex cord tumor," a recently described testicular neoplasm characterized by EWSR1::ATF1 gene fusion and aggressive clinical behavior. Due to the aggressive nature of this entity and the limited response to current treatment options available, identification of potential biomarkers for early diagnosis and targeted therapies are critical. This case report provides important insights into the genomic landscape of testicular sex cord-stromal tumors, especially within the CTNNB1-negative subset of patients with an aggressive clinical course, and further supports the distinction of "inflammatory and nested testicular sex cord tumor" as a separate entity from Sertoli cell tumors due to its characteristic morphological, immunohistochemical and molecular, features and clinical behavior.

Complete mimicry: Rhabdomyosarcoma with FUS::TFCP2 fusion masquerading as carcinoma-diagnostic challenge and report of two cases.

Rhabdomyosarcomas (RMS) are malignant mesenchymal tumors with skeletal muscle differentiation which are classified into alveolar, embryonal, pleomorphic, and spindle cell/sclerosing RMS. Within the spindle cell/sclerosing RMS tumor type there is a recently recognized sub-type categorized as intraosseous spindle cell RMS with TFCP2/NCOA2 gene fusion. This rare tumor is highly aggressive with predominant involvement of the craniofacial and pelvic bones with approximately 30 cases reported to date. Histopathologic features include spindle cell and epithelioid morphology with a characteristic co-expression of epithelial markers, myogenic markers, and ALK1 expression. We report two cases of gnathic spindle cell/sclerosing RMS with FUS::TFCP2 gene fusion that were initially interpreted as carcinomas by referring institutions and later reclassified when encountered in our practice after additional work-up and molecular characterization.

"Collecting duct carcinoma of the kidney: diagnosis and implications for management".

Collecting duct carcinoma of the kidney is a rare and aggressive subtype of renal cell carcinoma (RCC) arising from the distal convoluted tubules. At the time of diagnosis, patients are more frequently symptomatic, with advanced locoregional stage, and have metastatic disease. The 2016 WHO Classification of Tumours of the Urinary System defined diagnostic criteria for this entity. However, the diagnostic features continue to evolve, with typical, but not entirely specific, histologic and immunophenotypic characteristics. In addition, the lack of consistent molecular alterations makes collecting duct carcinoma a diagnosis of exclusion, with historical cases being re-classified as fumarate hydratase deficient RCC, ALK rearranged RCC, renal medullary carcinoma or high-grade urothelial carcinoma. The rarity and poor prognosis of the tumor makes it difficult to reach consensus guidelines to guide therapy. In this manuscript we review the clinicopathologic features of collecting duct carcinoma including pathologic diagnostic criteria, molecular characteristics and differential diagnosis, and their possible implications for management.

JAK2, PD-L1, and PD-L2 (9p24.1) amplification in metastatic mucosal and cutaneous melanomas with durable response to immunotherapy.

As immune checkpoint inhibitors are rapidly developing into the standard of care for patients with advanced melanoma, the value of diagnostic metrics to predict response to immunotherapy is steadily increasing. Next-generation sequencing-based parameters include tumor mutation burden (TMB) and genomic amplification of PD-L1/PD-L2/JAK2 at 9p24.1. At present, there are limited studies documenting response to checkpoint blockade in 9p24.1-amplified solid tumors. Herein, we have compared a cutaneous melanoma with a mucosal melanoma, both with 9p24.1 amplifications and durable response to immunotherapy. Although the cutaneous melanoma had a high TMB, the mucosal melanoma had a lower TMB compared with the mean TMB for all melanomas within the institutional clinical sequencing cohort. In summary, PD-L1/PD-L2/JAK2 amplification was associated with durable response to therapy for both cases, and this genomic signature is a potential valuable metric in predicting response to immunotherapy.

Novel PLAG1 Gene Rearrangement Distinguishes a Subset of Uterine Myxoid Leiomyosarcoma From Other Uterine Myxoid Mesenchymal Tumors.

Genetic alterations in uterine myxoid leiomyosarcoma are unknown. We investigate the clinicopathologic features of 19 uterine tumors previously diagnosed as myxoid leiomyosarcomas in which tumoral RNA was subjected to targeted RNA sequencing. PLAG1, BCOR, BCORL1, HMGA2, and ALK break-apart fluorescence in situ hybridization (FISH) and BCOR, PLAG1, and ALK immunohistochemistry were performed in cases which failed or lacked fusions by sequencing. The diagnosis of myxoid leiomyosarcoma was confirmed in 15 cases after exclusion of 4 tumors with BCOR and ALK rearrangements. These 15 patients presented at a median age of 50 years with stage I (3), II (2), III (2), and IV (1) tumors, respectively; stage was unknown in 7 cases. Tumor size ranged from 10 to 24 cm. Matrix was myxoid in all tumors and also eosinophilic in 2. Cells were spindled, epithelioid, and both in 10, 2, and 3 tumors and showed mild, moderate, and severe nuclear atypia in 3, 8, and 4 tumors, respectively. Mitotic index ranged from <1 to 14/10 HPF, while tumor necrosis was present in 6 (40%). Novel TRPS1-PLAG1 or RAD51B-PLAG1 fusions were detected by sequencing in 4 tumors, 3 of which were also confirmed by FISH. Diffuse PLAG1 expression was seen in 7 tumors, including 4 with PLAG1 rearrangement. No morphologic differences were seen among PLAG1 fusion-positive and fusion-negative tumors. No PLAG1, HMGA2, ALK, BCOR, or BCORL1 rearrangements were detected by FISH in 11 tumors. On the basis of sequencing and FISH results, PLAG1 rearrangements resulting in PLAG1 expression underpin ~25% of myxoid leiomyosarcomas and may serve as a useful diagnostic biomarker. Immunohistochemistry, targeted RNA sequencing, and/or FISH may distinguish myxoid leiomyosarcoma from its morphologic mimics.

Next-Generation Sequencing-Based Assessment of JAK2, PD-L1, and PD-L2 Copy Number Alterations at 9p24.1 in Breast Cancer: Potential Implications for Clinical Management.

Genomic amplification at 9p24.1, including the loci for JAK2, PD-L1, and PD-L2, has recently been described as a mechanism of resistance in postchemotherapy, triple-negative breast cancer. This genomic signature holds significant promise as a prognostic biomarker and has implications for targeted therapy with JAK2 inhibitors, as well as with immunotherapy. To guide future screening strategies, the frequency of these alterations was determined. A total of 5399 cases were included in the study. This encompassed 2890 institutional cases tested by the Memorial Sloan Kettering-Integrated Mutation Profiling of Actionable Cancer Targets assay and 2509 cases from The Cancer Genome Atlas (TCGA). The combined incidence of 9p24.1 amplifications in both the Memorial Sloan Kettering-Integrated Mutation Profiling of Actionable Cancer Targets and TCGA cohorts was 1.0% (56/5399 cases) and showed a >10-fold higher incidence in triple-negative breast cancer (triple-negative: 5.1%; non-triple-negative: 0.5%). Tumor mutation burden and stromal tumor infiltrating lymphocytes, parameters used to assess response to immunotherapy, were not significantly higher for these cases. The significance of genomic losses at 9p24.1 is unclear, and further studies are needed. Herein, we studied the spectrum of copy number alterations in breast cancer cases within our institutional clinical sequencing cohort and those profiled by TCGA to determine the frequency of genomic alterations that may predict response or resistance to JAK2 inhibitors and/or immunotherapy.

CK20 and p53 Immunohistochemical Staining Patterns in Urinary Bladder Specimens With Equivocal Atypia.

CONTEXT: - Urinary bladder flat carcinoma in situ (CIS) is a worrisome lesion, requiring aggressive surveillance and treatment. Cytokeratin 20 (CK20) and p53 are common immunohistochemical antibodies used to supplement CIS diagnosis in biopsy samples. However, existing data come primarily from unequivocally benign and malignant specimens. OBJECTIVE: - To correlate these markers in specimens with borderline histology with outcomes. DESIGN: - CK20 and p53 immunohistochemistry was analyzed for staining pattern, classified as CIS pattern (both stains yielding strong labeling of the area of concern), discordant (only 1 stain yielding CIS pattern), indeterminate (1 or both stains yielding partial or equivocal labeling), or benign (both stains yielding a benign pattern). RESULTS: - Specimens with equivocal atypia (n = 69) from 65 patients were studied. There were 9 specimens (13%) that had a CIS staining pattern, 18 (26%) were discordant, 31 (45%) were indeterminate, and 11 (16%) were benign. Of the discordant specimens, 13 labeled for CK20 but not p53, whereas 5 showed the opposite. Most specimens (n = 47; 68%) were obtained from patients with a known history of bladder cancer, of which recurrence developed in 27, with an average interval of 37 months (range, 2-216 months). A subset (n = 22; 34%) had no prior history of bladder cancer, from which only 1 patient with CK20-positive/p53-equivocal staining later developed diagnostic carcinoma. CONCLUSIONS: - In our cohort of specimens with equivocal urothelial atypia, very few patients without a prior diagnosis of bladder cancer progressed to diagnostic cancer (1 of 22), suggesting that staining results should be interpreted with caution in de novo atypia. Patients with a known history of bladder cancer had a substantial rate of recurrence, independent of staining pattern.

ZC3H7B-BCOR high-grade endometrial stromal sarcomas: a report of 17 cases of a newly defined entity.

High-grade endometrial stromal sarcoma likely encompasses underrecognized tumors harboring genetic abnormalities besides YWHAE-NUTM2 fusion. Triggered by three initial endometrial stromal sarcomas with ZC3H7B-BCOR fusion characterized by high-grade morphology and aggressive clinical behavior, we herein investigate the clinicopathologic features of this genetic subset by expanding the analysis to 17 such tumors. All of them occurred in adult women with a median age of 54 (range, 28-71) years. They were predominantly based in the endomyometrium and demonstrated tongue-like and/or pushing myometrial invasion. Most were uniformly cellular and displayed haphazard fascicles of spindle cells with mild to moderate nuclear atypia. Myxoid matrix was seen in 14 of 17 (82%) tumors, and collagen plaques were seen in 8 (47%). The mitotic index was ≥10 mitotic figures/10 high-power fields (HPFs) in 14 of 17 (82%) tumors with a median of 14.5 mitotic figures/10 HPFs. No foci of conventional or variant low-grade endometrial stromal sarcoma were seen. All tumors expressed CD10 with only limited or absent desmin, SMA and/or h-caldesmon staining. ER and PR expression in >5% of cells was seen in 4 of 12 (33%) tumors. Diffuse cyclin D1 and BCOR immunoreactivity was present in 7 of 8 (88%) and 7 of 14 (50%) tumors, respectively. Fluorescence in situ hybridization or targeted RNA sequencing confirmed ZC3H7B-BCOR fusion in all tumors, including four and two previously diagnosed as myxoid leiomyosarcoma and undifferentiated uterine sarcoma, respectively. Limited clinical data suggest that patients present at higher stage and have worse prognosis compared with published outcomes in low-grade endometrial stromal sarcoma. Tumors with ZC3H7B-BCOR fusion constitute a distinct group of endometrial stromal sarcomas with high-grade morphology that should be distinguished from other uterine mesenchymal neoplasms that may demonstrate myxoid morphology.

BCOR is a robust diagnostic immunohistochemical marker of genetically diverse high-grade endometrial stromal sarcoma, including tumors exhibiting variant morphology.

Recognition of high-grade endometrial stromal sarcoma is important because of its aggressive clinical behavior. Morphologic features of YWHAE-NUTM2 high-grade endometrial stromal sarcoma may overlap with other uterine sarcoma types. BCOR immunoexpression was studied in these tumors and their morphologic mimics to assess its diagnostic utility. BCOR immunohistochemical staining was performed on archival tissue from 28 high-grade endometrial stromal sarcomas with classic morphology (20 YWHAE-NUTM2, 5 ZC3H7B-BCOR, 3 BCOR-ZC3H7B), 3 high-grade endometrial stromal sarcomas with unusual morphology and unknown gene rearrangement status, 66 low-grade endometrial stromal sarcomas, 21 endometrial stromal nodules, 38 uterine leiomyosarcomas, and 19 uterine leiomyomas. Intensity of nuclear staining and percentage of positive tumor cells were recorded. Strong diffuse nuclear BCOR staining (defined as >95% of tumor cells) was seen in the round cell component of all 20 (100%) classic YWHAE-NUTM2 high-grade endometrial stromal sarcomas and the 3 unusual high-grade endometrial stromal sarcomas which prompted FISH studies confirming YWHAE rearrangement in 2 tumors. Genomic PCR confirmed the presence of BCOR exon 16 internal tandem duplication in the third case. Diffuse BCOR staining was strong in three and weak in one BCOR-rearranged high-grade endometrial stromal sarcoma while absent in the remaining four BCOR-rearranged tumors. BCOR staining was weakly positive in <5% of tumor cells in 4 of 66 (6%) low-grade endometrial stromal sarcomas and 1 of 18 (6%) endometrial stromal nodules and weakly to moderately positive in <5-40% of tumor cells in 6 of 31 (19%) leiomyosarcomas. No BCOR staining was seen in the remaining low-grade endometrial stromal sarcomas, endometrial stromal nodules, leiomyosarcomas, or any of the leiomyomas. BCOR immunohistochemical staining is a highly sensitive marker for YWHAE-NUTM2 high-grade endometrial stromal sarcoma with both classic and unusual morphology and identifies a subset of high-grade endometrial stromal sarcoma with BCOR alterations, including BCOR rearrangement and internal tandem duplication.

Updates in Benign Lesions of the Genitourinary Tract.

The genitourinary tract is a common site for new cancer diagnosis, particularly for men. Therefore, cancer-containing specimens are very common in surgical pathology practice. However, many benign neoplasms and nonneoplastic, reactive, and inflammatory processes in the genitourinary tract may mimic or cause differential diagnostic challenges with malignancies. Emerging clinicopathologic, immunohistochemical, and molecular characteristics have shed light on the pathogenesis and differential diagnosis of these lesions. This review addresses differential diagnostic challenges related to benign genitourinary tract lesions in the kidney, urinary bladder, prostate, and testis, with emphasis on recent advances in knowledge and areas most common in diagnostic practice.

Prostate biopsy and radical prostatectomy Gleason score correlation in heterogenous tumors: proposal for a composite Gleason score.

When prostate biopsy cores are separately identified in multiple containers, current recommendations are to grade each specimen individually. For treatment algorithms, the highest Gleason score (HGS) is typically used as the overall score, even if a lower score predominates. This practice has the potential to misrepresent the overall cancer in the entire gland for some patients and place them in a higher-grade group. We compare a novel composite Gleason score (CGS), integrating grade patterns from contiguous positive biopsy sites, with HGS to determine correlation with the radical prostatectomy (RP) Gleason score (GS). One hundred needle biopsy cases from 2008 to 2012 with >2 GSs in a biopsy set (eg, 3+3=6, 3+4=7, and 4+3=7) or more than a 1-step difference in GS (eg, 3+4=7 and 4+4=8 without 4+3=7) were analyzed. Grades were assigned using both methods (HGS and CGS) and compared with RPGS. Grade groups I to V were used to define downgrade and upgrade. Comparing HGS with RPGS, 31% remained the same and 69% had a change in GS (87% downgraded and 13% upgraded). Comparing CGS with RPGS, 59% remained the same and 41% had a change in GS (10% downgraded and 90% upgraded). Of the 2 methods, the CGS showed better overall correlation with RP (P<0.001) and was less likely to be downgraded compared with HGS. CGS correlates better with RPGS than HGS when >2 grades are present in a biopsy set. CGS has a significantly lower rate of downgrade and predicts the RPGS more accurately than HGS.

Does discontinuous involvement of a prostatic needle biopsy core by adenocarcinoma correlate with a large tumor focus at radical prostatectomy?

When prostate needle biopsies are involved discontinuously by tumor, no consensus remains on the optimal method of tumor quantification. We investigated whether discontinuous biopsy involvement usually results from a large tumor focus or multiple small foci. Prostate needle biopsies with discontinuous tumor and corresponding whole-mounted radical prostatectomies from 2008 to 2013 were analyzed. Linear length and percentage of biopsy involvement were measured both including and subtracting the benign intervening tissue. The corresponding region of the prostatectomy specimen was evaluated for tumor size and multifocality. From over 800 biopsy sets and 400 prostatectomies performed annually, 40 patients met inclusion criteria. Excluding benign tissue, length and percentage of biopsy involvement ranged from 1 to 7 mm and 5% to 66% (median 2.5 mm, 20%), whereas including intervening tissue yielded 4 to 15.5 mm and 25% to 100%, (median 7 mm, 70%), respectively. Benign intervening tissue measured from 2 to 10.5 mm (median 3.5 mm). In 31 patients (78%), a single tumor focus was present in the corresponding region of the prostate (the dominant tumor in 25/31). In 9 patients, multiple small foci were present. Eleven patients could have been excluded from active surveillance eligibility by measuring tumor from end to end (>50% involvement), of whom only 1 met criteria for clinically insignificant cancer at prostatectomy. Discontinuous tumor in a prostate biopsy often results from a single tumor focus in the corresponding region of the prostate (78%). Therefore, we recommend that an end-to-end measurement be provided, with accompanying diagnostic comment that this often correlates with the size of a single tumor focus.