American Journal of Surgical Pathology最新文献

GLI1-altered tumors form a diverse group occurring in various anatomic locations. In the alimentary tract, the most established are gastroblastoma, a biphasic epithelial-mesenchymal neoplasm of the stomach, and plexiform fibromyxoma, a pure spindle cell neoplasm. The spectrum of GLI1-rearranged gastrointestinal tumors has recently expanded with reports of cases in other parts of the GI tract, some exhibiting gastroblastoma-like features and others being pure mesenchymal neoplasms. These tumors often display a nonspecific immunophenotype, with only CD56 and cyclin D1 expression being common. Biphasic GLI1-altered tumors show diffuse keratin positivity in the epithelial component only, and GLI1-altered mesenchymal tumors typically lack or show only focal keratin expression. This study details 2 GLI1-rearranged gastrointestinal tract tumors with diffuse keratin and CD56 expression, composed entirely of epithelial cells with a nested growth pattern and finely stippled monotonous nuclei, leading to an initial suspicion of neuroendocrine tumor in both cases, despite lack of synaptophysin and chromogranin expression. Diffuse strong nuclear cyclin D1 expression was seen in both cases, and conversely, strong cyclin D1 staining was only seen in 5.4% (4/74) of well-differentiated neuroendocrine tumors tested. These 2 GI tract neoplasms highlight a widened spectrum of GLI1-rearranged tumors, now including monophasic epithelial neoplasms with diffuse keratin expression.

The category of ALK -rearranged mesenchymal neoplasms has been evolving rapidly, with reports of morphologically diverse lesions of cutaneous, soft tissue, and visceral origin. While some of these represent morphologically defined entities harboring recurrent ALK fusions (inflammatory myofibroblastic tumor and epithelioid fibrous histiocytoma), others are unclassified by morphology with variable overlap with the tyrosine kinase family of neoplasia and their underlying ALK fusions cannot be suspected based on morphology. We herein report 3 cases that expand the anatomic, morphologic, and genotypic spectrum of ALK -rearranged unclassified neoplasms. Patients were all adults aged 46 to 69 (median: 63) who presented with a mass located in the gingiva, subcutis of the back, and submucosal posterior pharyngeal wall. The tumor size ranged from 1 to 2.7 cm (median: 1.6). Conservative surgery was the treatment in all patients. Follow-up was available for one patient who remained disease-free at 14 months. Histologically, all tumors displayed large polygonal cells with foamy to granular and lipogenic-like microvacuolated copious cytoplasm and medium-sized round nuclei with 1 or 2 prominent nucleoli. Mitoses and necrosis were not seen. The initial diagnostic impression was PEComa, inflammatory rhabdomyoblastic tumor and unclassified pseudolipogenic neoplasm. Strong cytoplasmic ALK was detected by immunohistochemistry in all cases. Other positive markers include Cathepsin K (2/2), desmin (1/3), focal MyoD1 (1/1), focal SMA (1/3), and focal EMA (1/2). Targeted RNA sequencing revealed ALK fusions with exon 20 (2 cases) and exon 19 (one case) of ALK fused to RND3 (exon 3), SQSTM1 (exon 6), and desmin (intron 6). Methylation profiling in the desmin-fused case (initially diagnosed as inflammatory rhabdomyoblastic tumor) revealed an inflammatory myofibroblastic tumor match with a low confidence score of 0.5 and a flat copy number variation (CNV) profile. No NF1 mutation was detected in this case, altogether excluding an inflammatory rhabdomyoblastic tumor. Our study highlights and expands the morphologic and anatomic diversity of ALK- fused neoplasms and documents novel fusion partners ( RND3 and desmin).

Perivascular epithelioid cell neoplasms (PEComas) are tumors of uncertain cell lineage that occur across a wide age range, at a variety of anatomic sites, and with a female predominance. Most PEComas are associated with dysregulation of the mTOR pathway, most commonly through inactivating mutations of TSC2 or TSC1 . However, a small subset of PEComas are instead associated with TFE3 gene fusions. MITF is closely related to TFE3 and is frequently overexpressed in PEComas, often in a mutually exclusive manner with TFE3. Here we report the clinical, histopathologic, and molecular features of MITF-overexpressing PEComas in a series of 36 cases. The clinical and morphologic features were comparable to conventional PEComa, although the immunohistochemical profile was notable for the relatively limited expression of melanocytic markers, a surprising finding given that MITF is the master regulator of melanocytic differentiation. At the molecular level, 20 cases (56%) showed supernumerary copies of the MITF gene, suggesting a potential explanation for MITF overexpression. A putative genetic driver event within the mTOR pathway was identified in 11 of 15 cases (73%) analyzed by DNA or RNA sequencing. Interestingly, the malignant PEComas showed 2 distinguishing molecular features: they were associated with a complex chromosomal copy number profile, and they tended to show additional genetic changes, most commonly inactivating events involving TP53 , RB1 , and ATRX . These results elucidate key features of PEComas showing MITF overexpression, begin to explain the molecular basis for MITF overexpression in some PEComas and identify potential molecular correlates for malignancy that may be applicable to the broader PEComa family.

Multiple biliary tumors rarely develop in patients without underlying chronic hepatobiliary disease. Those lesions are regarded as multifocal neoplasms if there is no interconnecting dysplasia. This study aimed to determine whether 2 separate tumors in the biliary tract represent true multifocal independent tumorigenesis or intraluminal implantation of a single neoplasm. Two separate biliary tumors without intervening dysplasia were identified in 9 cases: biliary intraductal papillary neoplasm (IPNB; n=5) and extrahepatic cholangiocarcinoma (n=4). The 2 tumors were histologically similar in all cases. In 5 metachronous cases, the second tumor developed 2 to 13 years after the complete resection of the first tumor. In 4 synchronous cases, 2 separate neoplasms were identified in a surgical specimen. The metachronous presentation was more common in IPNB cases, whereas the synchronous development was more frequent in cholangiocarcinoma cases. The second tumors in 4 metachronous cases (4/5; 80%) and smaller lesions in all synchronous cases (4/4; 100%) were located in a lower part of the biliary. Immunophenotypes of cytokeratins and mucin core proteins were almost identical between the 2 lesions. Next-generation sequencing also confirmed that the 2 neoplasms shared gene mutations involving KRAS , GNAS , APC , BRAF , CTNNB1 , SMAD4 , TP53 , or ARID1A in all cases. In conclusion, multiple biliary tumors without underlying chronic biliary disease are most likely due to intraductal implantation of a single neoplasm. Thick mucinous bile in IPNB and increasing use of trans-ampullary biliary interventions may contribute to this unique form of tumor extension.

Multifocal papillary thyroid carcinomas (PTCs) are common and the majority of the tumors harbor mutual BRAF p.V600E mutation. This study aimed to investigate a contemporary series of multifocal PTCs with discordant molecular drivers. Consecutive thyroidectomies diagnosed with multifocal PTCs ≥0.5 cm between 2019 and 2023 were reviewed. Immunohistochemistry (IHC) for BRAF VE1 was performed for all tumors. Cases with discordant BRAF IHC results or morphologic discrepancy were identified, and BRAF IHC-negative tumors were subjected to RAS Q61R IHC and/or targeted RNA next-generation sequencing. A total of 770 patients with a main PTC ≥0.5 cm were identified; 255 (33.1%) had multifocal disease, and 142 (18.4%) had at least another PTC ≥0.5 cm. Among them, 13 cases (9.2%, 13/142) had discordant molecular drivers. Twelve cases had one or more BRAF -positive PTCs accompanied by a BRAF -negative PTC (3 with CCDC6::RET fusion, 1 with NCOA4::RET fusion, 1 with ACBD5::RET fusion, 2 with ETV6::NTRK3 fusion, 1 with TG::FGFR1 fusion, 1 with LMTK2::BRAF fusion, 1 with AGK::BRAF fusion and RAS p.Q61R mutation, 1 with RAS p.Q61R mutation, and 1 without detectable molecular drivers). The last case had tumors with discordant fusion drivers ( VIM::NTRK3 and TNS1::BRAF ). Most cases showed tumors that were morphologically distinct (92.3%, 12/13) and occurred in the contralateral lobes (76.9%, 10/13). Notably, we identified 4 cases (30.8%) that presented as collision tumors and 6 cases (46.2%) that showed lymph node metastases, including 2 with simultaneous involvement by tumors with discordant molecular drivers, as novel findings. In summary, a subset (9.2%) of multifocal PTCs had discordant molecular drivers and 84.6% of them were a combination of BRAF -positive and kinase gene fusion-associated PTCs, most with distinct morphologies. Almost half of the cases had nodal metastasis and a third of them showed simultaneous involvement by tumors with discordant molecular drivers. The results highlight the clinical importance of identifying such cases, given the potentially different treatments.

Epstein-Barr virus (EBV)-positive diffuse large B-cell lymphoma (DLBCL) is a rare form of aggressive B-cell lymphoma with limited molecular information reported regarding interferon regulatory factor 4 ( IRF4 ) status. Here, we presented 3 EBV-positive DLBCL cases with IRF4 rearrangement (EBV+DLBCL- IRF4 -R) verified by fluorescence in situ hybridization (FISH). Three patients, including 1 male and 2 females (median age: 64 y; range: 45 to 68 y), had normal immune function. During a median follow-up of 12 months (range: 0 to 24 mo), 2 patients succumbed to the disease, and 1 patient achieved complete response. Three tumors were present in the mediastinum, stomach, and thalamus, respectively. All three tumors exhibited DLBCL morphology and were identified as the non-germinal center B-cell subtype, with EBV-encoded small RNA positivity ranging from 70% to 80%. RNA sequencing was able to identify RHOH and IGH as fusion partners of IRF4 in two cases. No MYC and BCL2 rearrangements were detected in 3 cases by FISH and RNA sequencing. Next-generation sequencing revealed a low mutation burden, and only IRF4 was recurrently mutated in two EBV+DLBCL- IRF4 -R cases. Using the LymphGen 2.0 classifier, 1 case was classified as the MCD (including MYD88L265P and CD79B mutations) subtype. We report rare EBV+DLBCL- IRF4 -R that may enhance our understanding of the diverse spectrum of large B-cell lymphoma.

Pulmonary thrombotic arteriopathy (PTA) can be an incidental finding in lung resections performed for various indications. Historic studies largely examined PTA in autopsies. Thus, the prevalence in surgical samples, particularly in the modern era of lung cancer screening, is poorly defined. Detection of PTA in surgical samples may provide an opportunity for therapeutic intervention, but the impact of this finding on clinical management is unknown. We retrospectively examined consecutive lung surgical resections containing a report of incidental PTA between 2019 and 2022 in our institution. A retrospective chart review was performed to determine the history of systemic thromboembolism and clinical and radiographic follow-up. All slides were reviewed to morphologically characterize the vascular changes. Among 2930 pulmonary resections, 66 (2.3%) reportedly contained PTA. Twenty-four (36.4%) patients had a clinically recognized thromboembolic event either before or after surgical resection. Patients with clinically recognized thromboembolic disease were significantly more likely to have both acute and organized thrombi affecting large arteries. The presence of infarct, chronic hypertensive vasculopathy, or number of vessels with thrombi were not significantly associated with a clinically detected event. Reporting of incidental PTA led to clinical intervention in six patients and confirmed systemic thromboembolic disease in 2. Moreover, 2 patients with no further workup based on the incidental pathology findings subsequently developed pulmonary embolism. PTA is incidentally detected in 2.3% of surgical lung resections, and in two-thirds of cases, there is no clinical suspicion of thromboembolic disease. Pathologic reporting of PTA rarely led to clinical intervention, suggesting a need for improved communication of incidental pathology findings.

Primary sinonasal diffuse large B-cell lymphoma (PSDLBCL) is a rare aggressive lymphoma. Recently, genetic classification using Next Generation Sequencing (NGS) demonstrated that PSDLBCL largely consists of the MCD genotype, which has a poor prognosis mainly driven by MYD88 L265P and CD79B gene abnormalities. This study investigated the prevalence and clinicopathological significance of MYD88 L265P and CD79B Y196 mutations using droplet digital PCR in 55 patients with PSDLBCL, as well as the translocation of BCL2/BCL6/c-Myc with FISH. We found mutations in MYD88 L265P (29/55, 52.7%) and CD79B Y196 (20/55, 36.4%). The MCD-like subtype, defined by the mutation of MYD88 and/or CD79B, was found in 32 out of 55 cases (58.2%). This subtype largely consists of non-GCB type (31/32, 96.9%; P<0.01) and double-expressor cases (20/32, 62.5%; P=0.01) compared with the MYD88/CD79B co-wild type, with BCL6 translocation in a small subset (2/32, 6.3%) and no translocations of BCL2 (0/32) or c-Myc (0/32). The MCD-like subtype tended to relapse in specific sites such as the central nervous system, testis, and/or skin compared with the co-wild type (P=0.03), showing poorer outcomes in overall survival (P=0.02) and progression-free survival (P=0.01). In conclusion, our study highlights a high prevalence of MYD88 and CD79B mutations in PSDLBCL, identifying an aggressive MCD-like subtype with a distinct relapse pattern. This molecular subclassification can be helpful for both prognostic prediction and therapeutic strategy in patients with PSDLBCL.