[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.

[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.

[Clinicopathological study of large B-cell lymphoma with IRF4 rearrangement].

Objective: To study the clinicopathological features of large B-cell lymphoma (LBCL) with IRF4 rearrangement. Methods: Seven cases of LBCL with IRF4 rearrangement collected at the First Affiliated Hospital of Nanjing Medical University from November 2018 to October 2019 were evaluated by hematoxylin and eosin staining, immunohistochemistry and fluorescence in situ hybridization detection. The relevant literature was reviewed. Results: Four tumors were located in the tonsils, 2 tumors in the lymphoid nodes and one tumor in the adenoid.The patients were 3 males and 4 females patients with a median age of 24 years (range, 6 to 39 years).Microscopically, entirely follicular pattern was present in one case, entirely diffuse pattern in 2 cases, and follicular and diffuse pattern in other 4 cases. The tumor cells were medium to large in size and showed the morphology of centroblasts or blastoid cells with irregular nuclei, brisk mitotic activity in 3 cases and starry sky in 2 cases. All of the cases were positive for CD20, PAX-5, bcl-6, and MUM1 and had a Ki-67 index>80%, while CD10 and bcl-2 were positive in 3 cases. IRF4 gene rearrangement was identified in all cases and bcl-6 gene rearrangement in 2 cases. All patients presented with localized disease with clinical stage Ⅰ or Ⅱ, except one with stage Ⅳ at presentation and a new lesion in the mediastinum developed 8 months later. Conclusions: LBCL with IRF4 rearrangement is a clinicopathologically distinct entity. The observations reveal a broader spectrum of morphology and biological behaviors. The relationship between clinical stage and prognosis needs to be determined in more cases.

[Pulmonary artery intimal sarcoma: a clinicopathological analysis of three cases].

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.

[Atypical epithelioid hemangioendothelioma: a clinicopathological analysis of eight cases].

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 mm(2) 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.