[Clinical, imaging and pathological and molecular characteristics of simple bone cyst].

Objective: To investigate the radiologic, pathologic, and molecular features of simple bone cysts (SBC), and their differential diagnoses. Methods: Fourteen cases of SBC were collected at the Department of Pathology, the First Affiliated Hospital of Nanjing Medical University from 2017 to 2022, and fluorescence in situ hybridization (FISH) was performed for retrospective analysis. Results: There were 14 patients, including 7 females and 7 males, with age range of 7 to 45 (median 29) years. The most common complaint was pain, including 4 cases with pathological fracture and 5 with history of previous trauma. The tumor size ranged from 3.4 to 13.5 (median 5.6) cm. The lesion involved the femur (n=4), humerus (n=5) and iliac bone (n=5). Radiologic diagnoses included SBC, aneurysmal bone cyst, and giant cell tumor of the bone or its combination with aneurysmal bone cyst-like region and fibrous dysplasia. Histologically, the cyst walls of the lesions were composed of fibrous tissue, fibrin-like collagen deposits, bone-like matrix and occasional woven bone. The lesional cells were spindled to ovoid, with scattered osteoclast-like giant cells, foamy histiocytes, hemosiderin deposits and cholesterol clefts. In 6 cases there were nodular fasciitis-like areas. Immunohistochemically, the spindled to ovoid cells were positive for SMA, EMA and SATB2 in varying degrees. FISH detection was performed in all 14 cases and EWSR1/FUS rearrangement were found in 9 cases. One case of FUS::NFATC2 fusion was detected by next-generation sequencing. Nine cases of SBC with the rearrangement were more cellular, and there were more mitotic figures in the recurrent FUS::NFATC2 fusion tumor. Clinical follow-up was obtained in all 14 cases with the time ranging from 5 to 105 (mean 46) months. Amongst them, the tumor with FUS::NFATC2 rearrangement had local recurrence twice after the first local excision, but had no more recurrence or metastasis 34 months after the subsequent segmental resection. The other 13 cases had no recurrence. Conclusions: EWSR1 or FUS rearrangement is most commonly identified in SBC, suggesting that SBC might be a neoplastic disease. In cases where the radiologic appearance and histomorphology are difficult to differentiate from aneurysmal bone cyst, FISH detection can aid in the definitive diagnosis.

[Ewing's sarcoma of central nervous system: a clinicopathological analysis of six cases].

Objective: To investigate the clinicopathological characteristics, pathological diagnosis of Ewing's sarcoma of the central nervous system. Methods: Six cases of Ewing's sarcoma of the central nervous system diagnosed at the First Affiliated Hospital of Nanjing Medical University, Nanjing, China from 2015 to 2022 were collected. The clinical manifestations, histological morphology, immunophenotype and molecular genetics of these cases were analyzed. The related literature was reviewed. Results: There were four males and two females, with a male to female ratio of 2∶1. The onset age was 17-40 years, with a median age of 23 years. All 6 tumors were located in the spinal cord (2 cases of cervical vertebra, 1 case of thoracic vertebra, 2 cases of lumbar vertebra, and 1 case of sacral vertebra). The patients' clinical manifestations were mostly lumbago, weakness and numbness of lower limbs/limbs. In 1 case, the tumor recurred and metastasized to the suprasellar region and the third ventricle. Microscopically, the tumor showed diffuse infiltrative growth. In some cases, the tumor was closely related to the spinal meninges. The tumor cells were arranged in sheet, lobular, thin-rope, and nest-like patterns. Homer-Wright rosette was visible. The tumor cells were small to medium in size, and most of them had scant cytoplasm. A few cells had clear cytoplasm. Some areas were rhabdoid. The tumor cell nuclei showed focal mild pleomorphism. The chromatin was uniform and delicate while the nucleoli were not obvious. Mitosis was commonly seen. The tumor was separated by fibrous connective tissue and may be accompanied by mucinous degeneration. Immunohistochemistry showed that all tumors were positive for CD99, NKX2.2, Fli1, ERG. ATRX, H3K27me3, INI1 and BRG1 were all retained. Immunohistochemical stains for EMA, GFAP and Olig2 were negative. The Ki-67 proliferation index was 30%-70%. EWSR1 break-apart FISH test was positive. Conclusions: Ewing's sarcoma is rare in the central nervous system and needs to be distinguished from a variety of neoplasms with primitive undifferentiated small cell morphology. Immunohistochemistry and molecular genetics may be required for a proper diagnosis.

[Primary hepatic angiosarcoma: a clinicopathological analysis of nine cases].

Objective: To investigate the clinical manifestations, histomorphology, and differential diagnosis of primary hepatic angiosarcoma. Methods: Nine cases of primary hepatic angiosarcoma diagnosed in the Department of Pathology, the First Affiliated Hospital of Nanjing Medical University from January 2014 to December 2021 were collected, including biopsy and surgical specimens. The histomorphology, clinical, and radiologic findings were analyzed. The relevant literature was also reviewed. Results: There were six males and three females, aged 30 to 73 years (mean 57 years). Grossly, the growth pattern of the tumor was classified as either mass formation or non-mass formation (sinusoidal). Microscopically, the mass-forming primary hepatic angiosarcoma were further subdivided into vasoformative or non-vasoformative growth patterns; and those non-vasoformative tumors had either epithelioid, spindled, or undifferentiated sarcomatoid features. Sinusoidal primary hepatic angiosarcoma on the other hand presented with markedly dilated and congested blood vessels of varying sizes, with mild to moderately atypical endothelial cells. Follow-up in all nine cases revealed 8 mortality ranging from 1 to 18 months (mean 5 months) from initial diagnosis. One patient was alive with disease within a period of 48 months. Conclusions: Primary hepatic angiosarcoma is a rare entity with a wide spectrum of histomorphology, and often misdiagnosed. It should be considered when there are dilated and congested sinusoids, with overt nuclear atypia. The overall biological behavior is aggressive, and the prognosis is worse.

[Malignant peripheral nerve sheath tumor: a clinicopathological analysis].

Objective: To investigate the clinicopathological, immunophenotypic, and genetic features of malignant peripheral nerve sheath tumor (MPNST). Methods: Twenty-three cases of MPNST were diagnosed at the Jiangsu Province Hospital (the First Affiliated Hospital of Nanjing Medical University), China, between January 2012 and December 2022 and thus included in the study. EnVision immunostaining and next-generation sequencing (NGS) were used to examine their immunophenotypical characteristics and genomic aberrations, respectively. Results: There were 10 males and 13 females, with an age range of 11 to 79 years (median 36 years), including 14 cases of neurofibromatosis type I-associated MPNST and 9 cases of sporadic MPNST. The tumors were located in extremities (7 cases), trunk (4 cases), neck and shoulder (3 cases), chest cavity (3 cases), paraspinal area (2 cases), abdominal cavity (2 cases), retroperitoneum (1 case), and pelvic cavity (1 case). Morphologically, the tumors were composed of dense spindle cells arranged in fascicles. Periphery neurofibroma-like pattern was found in 73.9% (17/23) of the cases. Under low magnification, alternating hypercellular and hypocellular areas resembled marbled appearance. Under high power, the tumor cell nuclei were irregular, presenting with oval, conical, comma-like, bullet-like or wavy contour. In 7 cases, the tumor cells demonstrated marked cytological pleomorphism and rare giant tumor cells. The mitotic figures were commonly not less than 3/10 HPF, and geographic necrosis was often noted. Immunohistochemically, tumor cells were positive for S-100 (14/23, 60.9%) and SOX10 (11/23, 47.8%). The loss of the CD34-positive fibroblastic network encountered in neurofibromas was observed in 14/17 of the MPNST cases. The loss of H3K27me3 expression was observed in 82.6% (19/23) of the cases. Moreover, SDHA and SDHB losses were presented in one case. NGS revealed that NF1 gene loss of function (germline or somatic) were found in all 5 cases tested. Furthermore, four cases accompanied with somatic mutations of SUZ12 gene and half of them had somatic mutations of TP53 gene, while one case with germline mutation in SDHA gene and somatic mutations in FAT1, BRAF, and KRAS genes. Available clinical follow-up was obtained in 19 cases and ranged from 1 to 67 months. Four patients died of the disease, all of whom had the clinical history of neurofibromatosis type Ⅰ. Conclusions: MPNST is difficult to be differentiated from a variety of spindle cell tumors due to its wide spectrum of histological morphology and complex genetic changes. H3K27me3 is a useful diagnostic marker, while the loss of CD34 positive fibroblastic network can also be a diagnostic feature of MPNST. NF1 gene inactivation mutations and complete loss of PRC2 activity are the common molecular diagnostic features, but other less commonly recurred genomic aberrations might also contribute to the MPNST pathogenesis.

[CIC-rearranged sarcoma with rhabdoid features: a clinicopathological analysis].

Objective: To investigate the histopathologic, immunohistochemical, molecular genetic characteristics of CIC-rearranged sarcoma (CRS) with rhabdoid features. Methods: The clinical and pathologic data of two cases of CRS diagnosed between 2019 and 2021 at the Department of Pathology, Jiangsu Province Hospital were analyzed. Immunohistochemical study and fluorescence in situ hybridization (FISH) were performed. The relevant literature was reviewed. Results: Both patients were female, one was 58 years old, with tumor located in left thigh; the other was 43 years old, with tumor located in left pelvic cavity. Microscopically, both tumors were composed of small to medium-sized round, oval cells, arranged in nodules or sheets. The tumor cells showed irregular nuclear outline, coarse chromatin with prominent nucleoli and brisk mitotic activity. Both cases showed rhabdoid phenotype with myxoid stromal changes. Immunohistochemically, both cases were positive for CD99 and c-myc. High WT1 reactivity was seen in classic area, with low reactivity in rhabdoid area. There was no INI1 lost in both cases. Both were negative for NKX2.2 and NKX3.1. By FISH both cases demonstrated convincing break-apart signals of CIC gene. One patient died of disease after 1 month, and the other died of disease after 3 months. Conclusions: CRS is a small round cell undifferentiated sarcoma of the bone and soft tissue defined by molecular genetic characteristics, and may show atypical morphologic and immunophenotypic characteristics such as rhabdoid features. A correct understanding of its rare morphologic and immunophenotypic characteristics, combined with molecular pathologic detection, is conducive to correct diagnosis.

[Epithelioid hemangioendothelioma with TFE3 translocation in soft tissue:a clinicopathological study].

Objective: To investigate the clinicopathological and molecular features, diagnosis and differential diagnosis of TFE3-rearranged epithelioid hemangioendothelioma (EHE). Methods Two cases of TFE3-rearranged EHE arising from soft tissues, diagnosed by the Pathology Department of the First Affiliated Hospital of Nanjing Medical University from 2013 to 2020 were observed. EnVision method was used for immunophenotyping, fluorescence in situ hybridization (FISH) was used to test TFE3 gene rearrangements and WWTR1-CAMTA1 fusion gene,and next-generation sequencing (NGS) was used to delineate the fusion transcripts. Results: Details of these two cases were as follows: case 1, male, 51 years old, with tumor in the right temporal region; case 2, female, 42 years old, with tumor in the right neck. The tumors showed progressive painless enlargement. Grossly, the tumor of case 1 was multinodular with unclear boundary and grayish red cut surface, while the tumor of case 2, originating from a vein, appeared as a firm, tan mass within vessel wall. Microscopically, both tumors showed moderate cellularity and were consisted of plump, epithelioid, or histiocytoid cells with eosinophilic cytoplasm and mild-to-moderate nuclear pleomorphism. Most of the tumor cells were arranged in solid or alveolar growth patterns, while some tumor cells showed intraluminal papillary growth pattern in case 1 and anastomosing vascular channels and extramedullary hematopoiesis in case 2. Immunohistochemically, the tumor cells showed diffuse positivity for CD31, CD34, ERG, and TFE3. FISH revealed TFE3 break-apart signals in two cases, but WWTR1-CAMTA1 gene fusion was not detected. NGS identified YAP1 (exon1)-TFE3 (exon6) fusion gene in case 2. Clinical follow-up information was available in both cases for a follow-up period of 15 and 59 months respectively. Patient 1 had a relapse 22 months after surgery, and was currently alive with the tumor. Patient 2 remained disease-free. Conclusions: TFE3-rearranged EHE is a rare molecular subtype of EHE, with accompanying characteristic morphologic features. However the morphologic spectrum remains under-recognized, and more experience is needed. Immunohistochemical and molecular examinations are helpful for the diagnosis and differential diagnosis of the disease.

[Clinicopathological features of inflammatory myofibroblastic tumor].

Objective: To investigate the clinicopathological diagnosis and differential diagnosis of inflammatory myofibroblastic tumor (IMT). Methods: Thirty-two cases of IMT collected at the People's Hospital of Jiangsu Province from May 2010 to May 2020 were evaluated for their clinical, histologic, immunohistochemical and genomic features, and relevant literature was reviewed. Results: There were 19 male and 13 female patients, with age ranging from 5 to 65 years (mean, 37 years). The tumors were located in the lung and mediastinum (10 cases), gastrointestinal tract and mesentery/omentum (12 cases), urinary bladder (5 cases), head and neck (3 cases), somatic soft tissue (1 case), and retroperitoneum (1 case). Four cases of epithelioid inflammatory myofibroblastic sarcoma (EIMS) were all located intra-abdominally. Histologically, the tumor cells were myofibroblasts and fibroblasts arranged in predominantly fusiform pattern, with variably edematous to myxoid background or sclerotic collagenized stroma, and variably mixed chronic or acute inflammatory cells infiltration. EIMS were composed mainly of epithelioid tumor cells, with myxoid stroma and numerous neutrophils. Immunohistochemically, the tumor cells expressed cytoplasmic ALK (25/32, 78%), whereas the four EIMS showed nuclear membrane ALK staining pattern. The tumor cells also expressed CKpan (8/19), SMA (24/32, 75%) and desmin (12/32, 38%); all four EIMS also showed strong positivity for desmin. Fluorescence in situ hybridization (FISH) for ALK gene rearrangement showed split apart signals in 12 of 15 cases, most commonly with atypical signals. Next-generation sequencing (NGS) was performed in three tumors and showed that one case of lower leg IMT harbored a novel CLIP2-ALK fusion, and two cases of EIMS harbored RANBP2-ALK fusion. Follow-up data were available in 29 patients. Twenty-two patients were alive with no evidence of tumor, four patients had tumor recurrences (three patients were treated with crizotinib and were alive with tumor), and three patients died of the disease (including two patients with EIMS). Conclusions: IMTs show a wide morphologic spectrum, and should be differentiated form a variety of benign or malignant tumors. Immunohistochemistry (ALKp80, ALKD5F3) and FISH (ALK break-apart probe) could assist the diagnosis of IMT, with NGS recommended for the atypical cases.

[Clinicopathological significance of cyclin D1 expression in Rosai-Dorfman disease].

Objective: To study the clinicopathological significance of cyclin D1 expression in Rosai-Dorfman disease (RDD). Methods: Seventeen cases of RDD were evaluated by HE, immunohistochemical staining and molecular genetic analysis. Expression of cyclin D1 was compared between RDDs and control group that included 29 cases of reactive histiocytosis, 9 cases of IgG4-related disease, and 2 cases of Erdheim-Chester disease. Results: Cyclin D1 was expressed in RDDs (17/17), reactive histiocytosis (11/29), IgG4-related diseases (3/9), and Erdheim-Chester disease (2/2), respectively, with nuclear staining in the RDD cells or proliferative histiocytes. Chi-square test showed that expression of cyclin D1 was significantly higher in RDDs than in reactive histiocytosis and IgG4-related diseases (P<0.01), but not in Erdheim-Chester diseases (P>0.05). The expression threshold for recalculating the percentage of cyclin D1 positive cells was 27.5% (AUC=0.981, P<0.01) by ROC curve. However, CCND1 gene had no rearrangement detected by fluorescence in situ hybridization, but with increased copies of gene in some RDD cells. ARMS-PCR analysis also did not detect KRAS, BRAF and NRAS gene mutations in any cases. Conclusions: Cyclin D1 may serve as an additional diagnostic marker for RDDs. Its high expression may be related to activation of MAPK pathway, but the pathogenetic significance of cyclin D1 in RDDs needs further study.