Nanopore DNA Sequencing Detected Chromothripsis-Induced PAFAH1B1::USP6 Rearrangement in Periosteal Solid Aneurysmal Bone Cyst Initially Diagnosed as Osteosarcoma.

An aneurysmal bone cyst (ABC) is a benign bone neoplasm that typically occurs during the first and second decades of life. ABC usually presents as a rapidly growing intramedullary expansile mass with multiple blood-filled cysts in the metaphysis of the long tubular bones. Here, we report a case of a periosteal solid ABC that was initially diagnosed as a high-grade surface osteosarcoma. A 10-year-old male was referred to our hospital for swelling and tenderness of the left upper arm. Radiography revealed periosteal mass without fluid-fluid levels. On performing open biopsy, the tumor showed hypercellular proliferation of uniform spindle to epithelioid cells with brisk mitotic activity (up to 12/2 mm2) and lace-like osteoid formation, which was diagnosed as a high-grade surface osteosarcoma. After one course of chemotherapy using adriamycin and cisplatin, peripheral sclerosis was conspicuous, which led to pathological review and revision of diagnosis as "possibly osteoblastoma." The patient was disease-free for 4 years after marginal resection and curettage. Retrospective nanopore DNA sequencing unexpectedly detected a PAFAH1B1::USP6 rearrangement. The fusion gene was further validated using reverse transcription-polymerase chain reaction and the diagnosis was revised to ABC. Chromothripsis involving chromosome 17 has also been identified. Methylation analysis classified the present tumor as an ABC or non-ossifying fibroma using t-distributed stochastic neighbor embedding and unsupervised hierarchical clustering. This case report highlights the utility of nanopore DNA sequencing for soft tissue and bone tumor diagnosis.

Metastasizing aneurysmal dermatofibroma initially diagnosed as angiosarcoma confirmed by CD63::PRKCD fusion gene detection with nanopore sequencing.

Dermatofibroma (DF) is a benign tumor that forms pedunculated lesions ranging in size from a few millimeters to 2 cm, usually affecting the extremities and trunks of young adults. Histopathologically, DF is characterized by the storiform proliferation of monomorphic fibroblast-like spindle cells. In addition to neoplastic cells, secondary elements such as foamy histiocytes, Touton-type giant cells, lymphoplasmacytes, and epidermal hyperplasia are characteristic histological features. Several histological variants, including atypical, cellular, aneurysmal, and lipidized variants, have been reported; cases with variant histologies are sometimes misdiagnosed as sarcomas. We present a case of metastasizing aneurysmal DF that was initially diagnosed as an angiosarcoma on biopsy. A 26-year-old woman was referred to our hospital with a gradually enlarging subcutaneous mass in her lower left leg. Positron emission tomography-computed tomography revealed high fluorodeoxyglucose uptake not only in the tumor but also in the left inguinal region. On biopsy, ERG and CD31-positive atypical spindle cells proliferated in slit-like spaces with extravasation, leading to the diagnosis of angiosarcoma. Histology of the wide-resection specimen was consistent with DF, and lymph node metastasis was also observed. Nanopore DNA sequencing detected CD63::PRKCD fusion and copy number gain, although CD63 was not included in the target region of adaptive sampling. This report highlights the importance of recognizing the unusual clinical, radiological, and pathological features of DF to avoid misdiagnosis, and the potential diagnostic utility of nanopore sequencer.

Fluorescence in situ hybridization-negative intra-articular myxoid liposarcoma with complex rearrangements involving EWSR1::DDIT3 detected using nanopore sequencing.

Myxoid liposarcoma (MLPS) is a rare sarcoma, typically arising in deep soft tissues during the fourth to fifth decades of life. Histologically, MLPS is composed of uniform oval cells within a background of myxoid stroma and chicken-wire capillaries. Genetically, MLPS is characterized by the FUS/EWSR1::DDIT3 fusion gene, which generally results from balanced interchromosomal translocation and is detectable via DDIT3 break-apart fluorescence in situ hybridization (FISH). Here, we report an unusual intra-articular MLPS case, negative for DDIT3 break-apart FISH but positive for EWSR1::DDIT3. An 18-year-old female was referred to our hospital complaining of an intra-articular mass in the right knee joint. Histologically, the tumor was mainly composed of mature adipocytes, brown fat-like cells, and lipoblasts. Nanopore sequencing detected DNA rearrangements between EWSR1 and DDIT3 and clustered complex rearrangements involving multiple chromosomes, suggesting chromoplexy. Methylation classification using random forest, t-distributed stochastic neighbor embedding, and unsupervised hierarchical clustering correctly classified the tumor as MLPS. The copy number was almost flat. The TERT promoter C-124T was also detected. This report highlights, for the first time, the potential value of a fast and low-cost nanopore sequencer for diagnosing sarcomas.

Dramatic response to entrectinib in a patient with malignant peripheral nerve sheath tumor harboring novel SNRNP70-NTRK3 fusion gene.

Neurotropic tropomyosin receptor kinase (NTRK) gene rearrangements have been reported in limited cases of sarcomas; however, to date, there has been only one report of such rearrangements in malignant peripheral nerve sheath tumors (MPNSTs). Herein, we describe a 51-year-old male patient with a buttock tumor arising from the sciatic nerve, which was diagnosed as MPNST with positive S-100 staining, negative SOX10 staining, and loss of trimethylation at lysine 27 of histone H3 (H3K27me3) confirmed by immunohistochemistry. Soon after the resection of the primary tumor, the patient was found to have pulmonary and lymph node metastases. Chemotherapy with eribulin and trabectedin showed limited effects. However, the patient responded rapidly to pazopanib, but severe side effects caused discontinuation of the treatment. RNA panel testing revealed a novel fusion gene between Small Nuclear Ribonucleoprotein U1 Subunit 70 (SNRNP70) gene and NTRK3 gene. Furthermore, loss of NF1, SUZ12, and CDKN2A genes was confirmed by DNA panel testing, which is compatible with a histological diagnosis of MPNST. SNRNP70 possesses a coiled-coiled domain and seems to induce constitutive activation of NTRK3 through dimerization. In fact, immunohistochemistry revealed diffuse staining of pan-TRK within tumor cells. Treatment with entrectinib, which is an NTRK inhibitor, showed a quick and durable response for 10 months. Although NTRK rearrangements are very rare in MPNST, this case highlights the importance of genetic testing in MPNST, especially using an RNA panel for the detection of rare fusion genes.

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.

Recurrent FOS rearrangement in proliferative fasciitis/proliferative myositis.

Proliferative fasciitis (PF) and proliferative myositis (PM) are rare benign soft tissue lesions, usually affecting the extremities of middle-aged or older adults. Presenting as poorly circumscribed masses, they histologically show bland spindle cell proliferation in a myxoid to fibrous background and a hallmark component of large epithelioid "ganglion-like" cells in various numbers, which may lead to their misdiagnosis as sarcoma. PF/PM has been long considered as reactive, akin to nodular fasciitis; however, its pathogenesis has remained unknown. In this study, we analyzed the FOS status in 6 PF/PMs (5 PFs and 1 PM). Five PF/PMs occurred in adults, all showing diffuse strong expression of c-FOS primarily in the epithelioid cells, whereas spindle cell components were largely negative. Using fluorescence in situ hybridization (FISH), all 5 c-FOS-immunopositive tumors showed evidence of FOS gene rearrangement in the epithelioid cells. RNA sequencing in 1 case detected a FOS-VIM fusion transcript, which was subsequently validated by reverse transcriptase-polymerase chain reaction, Sanger sequencing, and VIM FISH. The one pediatric PF case lacked c-FOS expression and FOS rearrangement. c-FOS immunohistochemistry was negative in 45 cases of selected mesenchymal tumor types with epithelioid components that may histologically mimic PF/PM, including pleomorphic sarcoma with epithelioid features and epithelioid sarcoma. Recurrent FOS rearrangement and c-FOS overexpression in PF/PM suggested these lesions to be neoplastic. FOS abnormality was largely restricted to the epithelioid cell population, clarifying the histological composition of at least 2 different cell types. c-FOS immunohistochemistry may serve as a useful adjunct to accurately distinguish PF/PM from mimics.

An autopsy case of prostatic rhabdomyosarcoma with DICER1 hotspot mutation.

Somatic hotspot DICER1 mutations, which frequently coexist with germline inactivating mutation (i.e., DICER1 syndrome), have been identified in various types of benign and malignant conditions. Herein, we report an autopsy case of prostatic rhabdomyosarcoma (RMS) with a hotspot DICER1 c.5125G>A (p.D1709N) mutation. A 26 year-old man presented with a prostatic mass, hematuria, and urinary retention. He underwent total pelvic exenteration, colostomy, ileal conduit construction and partial urethrectomy. Five months postoperatively, he developed multiple metastases to the lungs, brain, iliopsoas muscles and bones. He died of respiratory failure, and autopsy was performed. Microscopically, the tumor was primarily composed of uniform primitive mesenchymal cells infiltrating to the prostate with cambium layer. Rhabdomyoblasts and anaplastic cells were focally observed. Immunohistochemically, tumor cells were positive for desmin, myogenin, PAX7, HMGA2. Multinodular goiter was detected at autopsy. Because the morphology is similar to pleuropulmonary blastoma and DICER1-mutant RMS of the female genital tract, we tested and identified a hotspot DICER1 mutation with Sanger sequencing. Recognizing DICER1-mutant tumor is important because of its frequent association with germline DICER1 inactivation and potential therapeutic implication. Further research is needed to clarify whether this case can be classified as embryonal RMS with anaplasia or 'DICER1-associated sarcoma'.

Skeletal EWSR1-NFATC2 sarcoma previously diagnosed as Ewing-like adamantinoma: A case report and literature review emphasizing its unique radiological features.

Ewing-like adamantinoma (EAD) is a rare bone tumor. It remains unclear whether EAD belongs to adamantinoma, Ewing sarcoma (ES), or an independent category. Herein, we present a case of femoral sarcoma previously diagnosed as EAD in a 26-year-old woman. We observed amplified EWSR1 and NFATC2 fusion signals using fluorescence in situ hybridization. Prompted by its unique radiological features, we reviewed the current literature on skeletal EWSR1-NFATC2 sarcoma (ENS) and EAD. In addition to the similar histological features, we found that both ENS and EAD displayed similar characteristic radiological features, such as the tendency to occur in the diaphysis of long bones, cortical expansion and buttressing-type thickening, and bone surface involvement with saucer-like erosion without cortical destruction. We believe that these unique radiological features were related to its indolent behavior. Altogether, it is possible that previously reported EAD cases may be neither ES nor the classic adamantinoma but ENS. Further studies are needed to clarify the relationship between EAD and ENS.

Surgical margin for phosphaturic mesenchymal tumors in soft tissues: An analysis of the radiological histopathological correlation.

BACKGROUND: Phosphaturic mesenchymal tumors primarily cause tumor-induced osteomalacia, a rare paraneoplastic syndrome, and half occur in soft tissues. There are few reports about the surgical margins of these tumors. This study aimed to clarify the optimal surgical margin for phosphaturic mesenchymal tumors by analyzing radiological and histopathological features. METHODS: This study included eight cases, seven primary and one recurrent, of tumor-induced osteomalacia caused by soft-tissue phosphaturic mesenchymal tumors that were surgically treated between January 2000 and January 2019. We evaluated the radiological and histopathological features of all tumors and investigated the correlation of these features, the surgical margin, and recurrence of hypophosphatemia. RESULTS: The tumors were located in superficial (n = 5) and deep (n = 3) tissues. Six of the eight tumors had a clear boundary, but five had an irregular margin. Three tumors had a hypointense rim on T2-weighted images, indicating fibrous tumor encapsulation. Histopathological analysis revealed infiltrative growth in six of the eight tumors, which correlated with an irregular margin seen on imaging. Although there was no recurrence in patients treated with an intended wide margin >1 cm, one of the three patients treated with marginal tumor resection experienced a recurrence of hypophosphatemia, with histopathological analysis showing infiltration of subcutaneous fat. In contrast, two tumors with clear boundaries, regular margins, and fibrous capsule seen on imaging, had no infiltrative growth and were cured by marginal resection. In one recurrent case, tumor infiltration was observed in the previous surgical scar, which was not detected on preoperative imaging. CONCLUSIONS: Soft-tissue phosphaturic mesenchymal tumors with an irregular boundary seen on imaging tend to be infiltrative, especially into subcutaneous fat, and should be treated by at least a 1-cm wide margin resection. Tumors with a fibrous capsule with clear and regular margins are cured by marginal margin resection. These findings could inform surgeons' decisions regarding the resection of soft-tissue phosphaturic mesenchymal tumors.

Mesenchymal tumours with RREB1-MRTFB fusion involving the mediastinum: extra-glossal ectomesenchymal chondromyxoid tumours?

AIMS: Ectomesenchymal chondromyxoid tumour (ECT) is a rare benign intraoral tumour which almost exclusively presents as a small mass of the anterior dorsal tongue. Recently, the RREB1-MRTFB (previously known as MKL2) fusion gene has been identified in 90% of ECTs, all located in the tongue, emphasising its genetic distinctiveness. Here, we report two mesenchymal tumours involving the superior mediastinum of adult women with RREB1-MRTFB fusions. METHODS AND RESULTS: Both tumours presented as well-circumscribed paravertebral masses that were clinically suspected to be schwannoma. After fragmented resection, recurrence was not observed at 27 and 18 months. Although tumours were originally unclassifiable, next-generation sequencing detected identical RREB1 (exon 8)-MRTFB (exon 11) fusion transcripts, which were validated by reverse transcriptase-polymerase chain reaction, Sanger sequencing, and fluorescence in-situ hybridisation. Both tumours shared hyalinised areas with round cells embedded in a cord or reticular manner. The tumour cells showed mild nuclear atypia of possible degenerative type with very low mitotic activity, and were at least focally positive for S100, glial fibrillary acidic protein, smooth muscle actin and epithelial membrane antigen. Overall, these findings suggest that they may represent previously undescribed extra-glossal ECT involving the mediastinum. However, the histology was not classic for ECT, because that in case 2 was predominated by storiform growth of spindle cells, whereas the tumour in case 1 lacked myxoid change. CONCLUSIONS: We have provided the first evidence that RREB1-MRTFB fusion is not limited to tumours in the head region, and whether such tumours represent extra-glossal ECTs requires further research.

Frequent mutations of genes encoding vacuolar H+ -ATPase components in granular cell tumors.

Granular cell tumors (GCTs) are rare mesenchymal tumors that exhibit a characteristic morphology and a finely granular cytoplasm. The genetic alterations responsible for GCT tumorigenesis had been unknown until recently, when loss-of-function mutations of ATP6AP1 and ATP6AP2 were described. Thus, we performed whole-exome sequencing, RNA sequencing, and targeted sequencing of 51 GCT samples. From these genomic analyses, we identified mutations in genes encoding vacuolar H+ -ATPase (V-ATPase) components, including ATP6AP1 and ATP6AP2, in 33 (65%) GCTs. ATP6AP1 and ATP6AP2 mutations were found in 23 (45%) and 2 (4%) samples, respectively, and all were truncating or splice site mutations. In addition, seven other genes encoding V-ATPase components were also mutated, and three mutations in ATP6V0C occurred on the same amino acid (isoleucine 136). These V-ATPase component gene mutations were mutually exclusive, with one exception. These results suggest that V-ATPase function is impaired in GCTs not only by loss-of-function mutations of ATP6AP1 and ATP6AP2 but also through mutations of other subunits. Our findings provide additional support for the hypothesis that V-ATPase dysfunction promotes GCT tumorigenesis.

H3K27me3 deficiency defines a subset of dedifferentiated chondrosarcomas with characteristic clinicopathological features.

Dedifferentiated chondrosarcoma is a rare bone sarcoma, whose genetic background remains incompletely understood. Mutations in SUZ12 or EED, which encode polycomb repressive complex 2 (PRC2) components, and resulting deficiency in H3K27me3 are characteristic features of the majority of malignant peripheral nerve sheath tumors. Here, we investigated H3K27me3 and PRC2 status in dedifferentiated chondrosarcoma. Among 19 evaluable dedifferentiated chondrosarcoma cases, six (32%) showed immunohistochemical loss of H3K27me3 only in the dedifferentiated component, whereas the well-differentiated component retained H3K27me3. H3K27me3-deficient dedifferentiated chondrosarcoma occurred in two men and four women with a median age of 66. All of these tumors affected bones of the upper half of the body, with the ribs being preferentially involved, which represented a significantly different distribution compared to that in the 13 H3K27me3-intact dedifferentiated chondrosarcomas. H3K27me3-deficient dedifferentiated chondrosarcomas were histologically different from H3K27me3-intact dedifferentiated chondrosarcomas, as the former invariably demonstrated dedifferentiated histology with a striking similarity to classic malignant peripheral nerve sheath tumor, comprising sweeping to swirling fascicles of relatively uniform spindle cells. Heterologous rhabdomyoblastic differentiation, the focal presence of grade 3 chondrosarcoma histology, and a cartilaginous component in the metastatic sites were exclusively seen in some cases of H3K27me3-deficient dedifferentiated chondrosarcoma. In all three H3K27me3-deficient dedifferentiated chondrosarcomas that contained focal grade 3 histology, dedifferentiated components did not juxtapose to the grade 3 areas but transitioned abruptly from the grade 1-2 components. Targeted next generation sequencing, which was successfully performed on four H3K27me3-deficient dedifferentiated chondrosarcomas, identified an IDH2 mutation in one case and COL2A1 truncations in three cases. The dedifferentiated areas of three cases harbored SUZ12 or EED alterations, which were absent in the well-differentiated component, suggesting a role for PRC2 aberrations in dedifferentiation. H3K27me3 deficiency defines a novel subset of dedifferentiated chondrosarcoma that requires recognition because of its diagnostic and potential clinical implications.

Infiltrative nature of tumor-induced osteomalacia lesions in bone: Correlation between radiological and histopathological features.

OBJECTIVE: Tumor-induced osteomalacia is a rare paraneoplastic syndrome usually caused by phosphaturic mesenchymal tumors, which commonly occur in bone. This study aimed to investigate the radiological features of tumor-induced osteomalacia lesions in bone, and their correlation with its histopathology. MATERIALS AND METHODS: This study included 13 patients with tumor-induced osteomalacia treated between January 2000 and April 2018 at our hospital. All patients were surveyed to detect the tumor causing the condition. Diagnostic imaging studies of the suspected tumors were obtained before tumor removal. We evaluated the radiological features of all tumors, investigated histopathological findings in 10 cases that underwent surgery, and obtained evaluable tumor specimens. RESULTS: The tumors were classified into the following three types by CT: sclerotic (n = 4), lytic (n = 7), and mixed (n = 2). In two cases, lytic lesions focally invaded the surrounding cancellous bone, detected by the soft tissue-window of CT, not the bone-window. Histopathology revealed inter-trabecular invasion in all cases, regardless of radiological features. Osteoclasts were seen in lytic types, and creeping substitution-like thickened trabecular bone and calcification were observed in sclerotic types. In all cases, focal invasion of the tumor into cortical bone was seen. CONCLUSIONS: Tumor-induced osteomalacia lesions in bone showed a wide variety of radiological features, and tended to invade into cancellous and cortical bone. These findings suggest that extended curettage or resection of thinned cortical bone may be necessary. This might improve the cure rate of surgeries for tumor-induced osteomalacia lesions in bones.

INSM1 expression and its diagnostic significance in extraskeletal myxoid chondrosarcoma.

Extraskeletal myxoid chondrosarcoma is a rare subtype of sarcoma that affects the soft tissue and bones in middle-aged and elderly adults. Its diagnosis can be challenging, with the differential diagnoses including a wide variety of mesenchymal tumors. The line of differentiation of extraskeletal myxoid chondrosarcoma has been controversial, but recent evidence suggests a neuroendocrine phenotype. INSM1 is a zinc-finger transcription factor that plays a pivotal role in neuroendocrine differentiation, and has been proposed as a promising immunohistochemical marker of neuroendocrine carcinoma. The aim of this study was to determine the prevalence of INSM1 expression in extraskeletal myxoid chondrosarcoma and to understand its significance in sarcoma diagnosis. We immunostained the representative sections of 31 NR4A3-rearranged extraskeletal myxoid chondrosarcomas and 187 histological mimics. Nuclear staining of moderate or higher intensity in at least 5% of tumor cells was considered positive. Twenty-eight of the 31 extraskeletal myxoid chondrosarcomas (90%) were positive for INSM1, providing strong evidence for neuroendocrine differentiation. The staining was diffuse (>50%) in 17 cases, with most immunopositive tumors showing at least focal strong expression. The INSM1 staining extent was not correlated with cytomorphology, synaptophysin expression, or fusion types (EWSR1 vs non-EWSR1). In contrast, INSM1 expression was negative in 94% of the 187 other mesenchymal tumors. INSM1-positive mimics comprised a small subset of chordoma (1 of 10), soft tissue myoepithelioma (1 of 20), ossifying fibromyxoid tumor (3 of 10), and Ewing sarcoma (3 of 10), among other tumor types. The majority of these cases showed labeling in <25% of the tumor cells. Although not entirely sensitive or specific, INSM1 could be a potential marker for the diagnosis of extraskeletal myxoid chondrosarcoma when molecular genetic access is limited.

Extraskeletal osteosarcoma: MDM2 and H3K27me3 analysis of 19 cases suggest disease heterogeneity.

AIMS: Extraskeletal osteosarcoma (ESOS) is a sarcoma in the non-skeletal tissue that directly produces neoplastic osteoid or bone. De-differentiated liposarcoma (DDLPS) and malignant peripheral nerve sheath tumour (MPNST) are the two most common types of sarcoma that can harbour heterologous osteosarcomatous differentiation. We aimed to determine the potential relationship of ESOS to DDLPS and MPNST. METHODS AND RESULTS: We investigated MDM2 and H3K27me3 status in 19 cases of ESOS, two of which contained a low-grade component. The ESOS affected deep soft tissues (n = 10), superficial soft tissues (n = 3) and organs (n = 6). Among 10 deep soft-tissue ESOS, six showed MDM2 amplification, four of which also harboured CDK4 co-amplification. Both ESOS with a low-grade component showed co-amplification for MDM2 and CDK4. Among the six organ-based ESOS three giant cell-rich ESOS showed an H3K27me3 deficiency (one in primary and two in metastatic sites). Using targeted next generation sequencing, an H3K27me3-deficient ESOS showed EED homozygous deletion, while none of the three showed alterations in NF1, CDKN2A or SUZ12 genes. During median follow-up of 20 months, all six patients with MDM2-amplified ESOS lived for 3-103 months, while two of the three patients with H3K27me3-deficient ESOS died from this disease in 4 and 20 months, respectively. CONCLUSION: We demonstrate that ESOS may include at least two small subsets: an MDM2-amplified deep soft-tissue ESOS (which may be related to DDLPS) and an H3K27me3-deficient organ-based ESOS (which is probably unrelated to MPNST). Larger studies are required to validate the present observations and investigate the clinical implications of such subcategorisation.

Urinary bladder urothelial carcinoma with concurrent plasmacytoid and micropapillary differentiations: A report of two cases with an emphasis on serum carbohydrate antigen 19-9.

We report two cases of urinary bladder urothelial carcinoma (UC). In both, histological examination of a transurethral resection specimen of the bladder tumor revealed UC with plasmacytoid and micropapillary differentiations. In Case 1, residual plasmacytoid UC deeply invaded the extravesical fat tissue of the radical cystectomy specimen, and metastatic carcinoma was found in almost all the dissected lymph nodes. Despite adjuvant chemotherapy and radiotherapy, the patient died 25 months postdiagnosis. Elevated serum carbohydrate antigen 19-9 (CA19-9) returned to near normal levels after radical cystectomy, but they increased shortly before death. In Case 2, no residual carcinoma was found in the radical cystectomy specimen or lymph nodes. Postoperative serum CA19-9 was maintained at normal levels, and the patient remains alive without recurrence or metastasis. Although plasmacytoid and micropapillary UC are known aggressive variants of UC, plasmacytoid UC may be more aggressive. Serum CA19-9 could serve as a useful biomarker to monitor progression of plasmacytoid UC.

CIC-Rearranged Sarcoma.

CIC-rearranged sarcoma is a rare type of small round cell sarcoma. The tumors often affect the deep soft tissues of patients in a wide age range. They are highly aggressive, respond poorly to chemotherapy, and have a worse outcome than Ewing sarcoma. CIC-rearranged sarcoma has characteristic and recognizable histology, including lobulated growth, focal myxoid changes, round to epithelioid cells, and minimal variation of nuclear size and shape. Nuclear ETV4 and WT1 expression are useful immunohistochemical findings. CIC fusion can be demonstrated using various methods; however, even next-generation sequencing suffers from imperfect sensitivity, especially for CIC::DUX4.

The diagnostic utility of cytology specimen in a case of EWSR1::NFATC2 sarcoma.

EWSR1::NFATC2 sarcoma, a rare round cell sarcoma constituting the majority of EWSR1::non-ETS sarcomas, has recently been defined in the latest WHO classification. To date, the cytological findings of EWSR1::NFATC2 sarcoma remain undocumented. We present the case of a 25-year-old man with a history of polyostotic fibrous dysplasia in the right leg, referred to our hospital with left thigh pain. Cytological findings included metachromasia, minimally pleomorphic round cells, and eosinophilic infiltration. There was no precursor fibrous dysplasia and the initial diagnosis was undifferentiated pleomorphic sarcoma. Following histologic review, we successfully performed immunocytochemistry and fluorescence in situ hybridization (FISH) on archival cytology specimens. The tumor cells were positive for NKX2-2, NKX3-1, and PAX7 and showed amplified 5' single signals of EWSR1 gene. Reverse transcriptase-polymerase chain reaction revealed an in-frame fusion of EWSR1 and NFATC2. This report describes the cytological features of EWSR1::NFATC2 sarcoma and highlights the diagnostic utility of archival cytology specimens.