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.

Objective:To investigate clinical, histopathological, molecular genetic characteristics, and immunophenotypes of superficial CD34-positive fibroblastic tumor (SCPFT) .Methods:The pathological data were collected from 19 cases of SCPFT from January 2015 to July 2022 in the First Affiliated Hospital of Nanjing Medical University, and analyzed retrospectively.Results:In total, 19 cases of SCPET were enrolled, including 8 males and 11 females. Their age at onset ranged from 16 to 67 years, and the disease duration ranged from 3 months to 3 years. Tumors occurred in the thigh (6 cases), back (4 cases), shoulder (3 cases), abdominal wall (2 cases), popliteal fossa (1 case), lower leg (1 case), foot (1 case) and forehead (1 case). The tumor lengths were 0.8 - 4 (2.36 ± 0.76) cm, with relatively clear borders. Surgical excision was performed in all the 19 cases, and 1 case experienced recurrence. Histopathological examination showed that tumors were located in the dermis and subcutis, and infiltrated the peripheral fat tissues or the dermis; tumors were composed of abundant spindle cells and polygonal cells arranged in interlacing fascicles; cells with nuclear pleomorphism were observed in all cases, and were characterized by large, hyperchromatic and irregular nuclei, intranuclear pseudoinclusions, and prominent nucleoli; the mitotic figure was rare, and tumor necrosis was not found; inflammatory cell infiltration to different extents was observed in the tumor stroma, and lymphocyte sheaths were observed around the tumors in 2 cases. Immunohistochemical staining showed strong diffuse expression of CD34 in the tumor cells in all the 19 cases, the Ki-67 proliferation index was < 10% in 18 cases, and CKpan (2/12), desmin (2/15), and smooth muscle actin (1/19) were focally expressed. Fluorescence in situ hybridization for the detection of PRDM10 gene rearrangements was performed in 3 cases, and identified PRDM10 rearrangements in 2 cases, including 1 case of SCPFT accompanied by lymphocyte sheaths without EWSR1 rearrangements. Conclusion:SCPFT is an intermediate fibroblastic tumor with no characteristic clinical manifestations, often accompanied by PRDM10 rearrangements, and its diagnosis depends on histopathological patterns.

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.

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.

Objective: To investigate the histopathologic, immunohistochemical, molecular genetic characteristics of dedifferentiated liposarcomas with meningothelial-like whorls(DDLMW). Methods: Six cases of DDLMW diagnosed at Jiangsu Province Hospital(the First Affiliated Hospital of Nanjing Medical University) from March 2012 to August 2018 were enrolled. The cases were analyzed by routine HE staining, immunohistochemistry(MDM2, CDK4 and p16) and fluorescent in-situ hybridization(FISH) on MDM2 gene. Related literatures were also reviewed. Results: Three of the 6 patients were male.The patient ages ranged from 40 to 77 years (mean, 58 years). Four tumors occurred in the retroperitoneum and two in the mediastinum. Histologically, the tumors showed, in addition to foci of well-differentied liposarcoma, characteristic, scattered meningothelial-like concentrical whorls. The whorls were composed of tightly, concentrically arranged, spindle to ovoid cells with mild to mederate cytological atypia. Metaplastic bone was present within or in their immediate vicinity in four case. The tumors cell also showed strong and diffuse immunoreactivity to MDM2, CDK4 and p16, but no immunoreactivity to S-100 protein, SMA, SOX10, EMA, CD21, CD23 or CD35. The Ki-67 labeling indexes were low, while FISH showed high levels of MDM2 amplification in all cases. Conclusions DDLMW is a rare morphologic variant of dedifferentiated liposarcoma. The whorls in DDLMW do not represent perineurial or follicular dendritic differentiation. Recognition and familiarity with its existence, as well as combined application of immunohistochemical staining and MDM FISH, are important to avoid confusion with other lesions.

Objective:To investigate the clinicopathological characteristics, genetic features, diagnosis and differential diagnosis of pulmonary artery intimal sarcoma (PAIS).Methods:Three cases of PAIS were collected from Jiangsu Province People′s Hospital (from February 2016 to November 2019). The clinical data, imaging examination, morphology, immunostaining, and molecular changes were retrospectively analyzed.Results:There were 1 male and 2 females (age: 32, 50, 60 years), who had symptoms of cough, asthma or chest tightness. Imaging findings indicated low density filling defects which were suspected as thrombus, embolism or myxoma. Grossly, the main tumor was located in the elastic arteries and their lobar branches, also extended into the atrium and ventricle, with lung parenchymal infiltration focally. Microscopically, tumor cells were predominantly composed of abundant spindle cells with obvious atypia and myxoid background, resembling fibroblastic or myofibroblastic differentiation. Active mitotic figures and necrosis could be seen in some areas. Immunohistochemical staining of vimentin was strongly positive, while pan-cytokeratin, S-100, desmin, Fli-1, CD31, SMA and ERG etc were variably positive only in focal areas. FISH detection showed amplification of MDM2 gene in three cases and EGFR gene in two cases. Metastatic lesions were found in one case by 18, 32 and 42 months after surgery respectively. There was no recurrence or metastasis in the other two cases.Conclusions:PAIS is one of exceptionally poor differentiated mesenchymal tumor that arises from the arterial intima of elastic pulmonary arteries. There was no definite differention in morphology. Gene detection shows amplification of MDM2 and EGFR gene. This tumor often has poor prognosis with aggressive behavior. Complete resection is the only effective therapeutic option. There is disagreement as to whether chemotherapy and radiotherapy can improve survival.

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.

Objective: To investigate the clinicopathological features, diagnosis and differential diagnosis of dedifferentiated liposarcoma (DDLPS) with inflammatory myofibroblastic tumor (IMT)-like features. Methods: Five cases of DDLPS with IMT-like features were collected from the First Affiliated Hospital of Nanjing Medical University, the Affiliated Hospital of Nanjing University of Traditional Chinese Medicine and the First People′s Hospital of Qinzhou between 2013 and 2018. EnVision method and fluorescence in situ hybridization (FISH) were used to detect the immunophenotype of the tumor cells and the profile of MDM2 gene amplification respectively. Results: All five cases were male and the median age was 61 (range 53 to 65) years. The clinical symptoms were mainly related to the space-occupying lesions. The tumors were located in duodenal mesentery (two cases), intestinal wall (one case), retroperitoneum (one case), and spermatic cord (one case). Grossly, the tumors were not well encapsulated, ranging from 3 to 13 cm (median 6.7 cm) in diameter, with tan to gray and firm cut surface. Histologically, the dedifferentiated component closely resembled inflammatory myofibroblastic tumor (IMT), with spindle/polygonal/stellate-shaped cells arranged in storiform, sheet-like, or random pattern, with varying degrees of chronic inflammation and fibrosis. All three major patterns seen in IMT (myxoid, cellular and hypocellular fibrous) were observed, the hypocellular fibrous pattern was the most common. Well-differentiated liposarcomatous component was found in the peripheral areas of all the tumors. One case had high grade dedifferentiated component. Four cases were strongly positive for MDM2 and p16. Two cases were positive for SMA, and one case was focally positive for desmin and one for CD34. None of the cases stained for ALK-1. FISH demonstrated MDM2 gene amplification in all five cases. Clinical follow-ups were available in all five cases and the interval ranged from 3 to 66 months (median 23 months). Two patients developed recurrences and one patient had metastasis. The remaining two patients were alive with no evidence of tumor recurrence at 3 and 14 months after surgery respectively. Conclusions DDLPS with IMT-like features is a more aggressive neoplasm than its histological mimic (IMT), and should not be misdiagnosed as other intermediate or low-grade malignant tumors, such as IMT, sclerosing liposarcoma, inflammatory liposarcoma, aggressive fibromatosis, solitary fibrous tumors, low-grade myofibroblastic sarcoma, and low-grade fibrosarcoma.

Objective: To investigate the clinicopathological features and differential diagnosis of adamantinoma of long bone. Methods: Seven cases of adamantinoma on long bone were selected at Jiangsu Province People′s Hospital from June 2012 to May 2018. Clinicopathologic details, immunohistochemical and molecular analysis were performed,and the relevant literature reviewed. Results: There were 6 males and 1 female patients,age ranging from 21 to 60 years (mean 38 years). Six cases were on the right side and one case was on the left; in five cases the tumors arose from tibia, one from patella and one from humerus. Microscopically,tumour cells were mainly composed of spindle cells arranged in bundles or braids,with irregular epithelial island. Immunohistochemically,the epithelial island expressed high molecular weight cytokeratin but not CK8/18. Both epithelial and spindle components expressed vimentin. One case that was microscopically similar to intraosseous synovial sarcoma did not show SYT gene rearrangement. Clinical follow-up was available for five patients: one patient had axillary metastases seven months after operation, one patient had recurrence 34 months after surgery, 3 patients were uneventful with follow up duration from half a month to 32 months. Conclusion Adamantinoma occurring in long bones is very rare. The correct diagnosis requires adequate sample selection, careful morphologic observation, immunohistochemistry and molecular genetics.

Objective: To study the clinicopathological features, diagnosis, and differential diagnosis of atypical epithelioid hemangioendothelioma (EHE). Methods: Eight cases of atypical EHEs were collected from Jiangsu Province Hospital (the First Affiliated Hospital of Nanjing Medical University) between 2010 and 2018. EnVision method and fluorescence in situ hybridization (FISH) were used to detect immunophenotype, WWTR1-CAMTA1 and TFE3 gene rearrangement, respectively. Results: There were 4 males and 4 females, ranging from 42 to 59 years (median 47.5 years). The tumors located in soft tissue (3 cases), lung (3 cases), liver (1 case) and chest wall (1 case). One soft tissue EHE involved also adjacent fibula and pleural involvement was present in all three lung cases at the diagnosis. Regional lymph node metastases were present in two cases (one involving soft tissue tumor and one involving liver). Morphologically, the tumor cells were epithelioid with abundant eosinophilic cytoplasm, moderate to marked nuclear pleomorphism, irregular nuclear membrane, unevenly chromatin, and prominent nucleoli. The cells arranged in cords, small nests or solid pattern. The mitotic rate was 4.3 mitoses/2 mm² on average (ranging 2 to 9). Tumor necrosis was seen in every case. Among all 8 cases, blister cells were found upon careful observation. Myxohyaline stroma was present in 6 cases. Immunohistochemically, tumor cells expressed CD31 (8/8), CD34 (7/8), ERG (8/8), CKpan (2/7), and CAMTA1 (4/6). None of the tested cases stained for TFE3 (0/6). WWTR1-CAMTA1 fusion gene by FISH was found in all tested 6 cases and TFE3 gene rearrangement was not detected in any. Available clinical follow-up was obtained in 7 cases and the intervals range from 6 to 55 months (average 19.6 months). Six patients had metastasis and 3 patients died of disease. One patient was alive with no evidence of disease. Conclusions Atypical EHE is a more aggressive tumor than classic EHE, with histological features including high nuclear grade, increased mitotic activity, the presence of solid growth pattern and tumor necrosis. The differential diagnoses include epithelioid angiosarcoma, carcinoma and epithelioid sarcoma.