Diffuse Large B-Cell Lymphoma Manifesting as Miliary Nodules in the Lung: A Case Report.

Malignant lymphoma has various pulmonary manifestations on chest CT, including nodules, masses, areas of consolidation, and ground-glass opacity. These presentations can pose a diagnostic challenge, as they mimic other disease patterns. Herein, we report a case of diffuse large B-cell lymphoma (DLBCL) manifesting as miliary nodules in a 67-year-old male initially presenting with dyspnea and fever. Radiologic findings included diffuse, bilateral, multiple tiny nodules consistent with metastasis, miliary tuberculosis, and fungal infection. However, further investigations, including laboratory tests, imaging, and biopsies, led to the diagnosis of DLBCL involving the lungs. Herein we reported a rare case of lymphoma involvement of the lung presenting as miliary nodules. Accurate diagnosis relies on a comprehensive evaluation of the clinical history, physical features, laboratory test results, and imaging findings.

[Primary Malignant Peripheral Nerve Sheath Tumor of the Pulmonary Vein: A Case Report]. / íì •ë§¥ì˜ 원발성 ì• ì„± ë§ì´ˆì‹ ê²½ì´ˆì¢ : 증례 ë³´ê³ .

Primary masses rarely originate from the heart and great vessels, and a malignant peripheral nerve sheath tumor (MPNST) is extremely rare. A 76-year-old male with pleural effusion underwent contrast-enhanced computed tomography, which revealed a hypoattenuating mass involving the right pulmonary vein and left atrium. Ultrasonography showed that the mass originated from the right pulmonary vein. Surgical resection confirmed an MPNST that originated from the pulmonary vein. We report the first Korean case of a primary MPNST originating from the pulmonary vein. We have also described the radiologic findings suggestive of a pulmonary vein mass.

Do Histology and Primary Tumor Location Influence Metastatic Patterns in Bladder Cancer?

Metastasis is the leading cause of death in patients with bladder cancer. This study utilized a statistical analysis of patient data from the Surveillance, Epidemiology, and End Results database to examine the influence of histological type and primary site on the metastatic behavior of bladder cancer. Significantly different metastatic patterns were observed among bladder cancer patients depending on their histological type. Patients with squamous cell carcinoma showed a significantly (p < 0.001) lower bone metastasis rate (27.2%) than patients with urothelial carcinoma (UC) (38.3%). Patients with neuroendocrine carcinoma showed a significantly (p < 0.001) higher liver metastasis rate (52.1%) and a significantly (p = 0.001) lower lung metastasis rate (25.7%) than patients with UC (22.6% and 33.5%, respectively). UC patients also demonstrated differences in metastatic behavior according to histological subtype. The sarcomatoid subtype showed a significantly (p < 0.001) higher lung metastasis rate (51.6%) and a significantly lower (p = 0.002) lymph node metastasis rate (22.6%) than the micropapillary subtype (12.1% and 54.1%, respectively). Significant differences in metastatic behavior were also observed among patients with conventional UCs originating from the bladder, ureter, and renal pelvis. This study highlights the impact of histological characteristics and primary site on metastatic tendencies in bladder cancer, highlighting the importance of tailoring treatment and surveillance strategies.

The Metastasis Pattern of Renal Cell Carcinoma Is Influenced by Histologic Subtype, Grade, and Sarcomatoid Differentiation.

Background and Objectives: Metastasis is a major cause of death in renal cell carcinoma (RCC) patients; therefore, a better understanding of the metastatic process and the ability to predict metastasis in advance is important for treating patients with RCC. This study aimed to investigate whether histological subtypes of RCC and other factors, such as nuclear grade and sarcomatoid differentiation, could predict the probability and location of metastases in patients with RCC. Materials and Methods: Cases of clear-cell, papillary, chromophobe, and sarcomatoid RCC were retrieved and analyzed from the Surveillance, Epidemiology, and End Results databases. Results: When comparing the metastatic patterns among the three histologic subtypes, patients with clear-cell RCC were significantly more likely to have brain and lung metastases. Moreover, patients with papillary RCC were significantly less likely to develop bone metastases and more likely to develop lymph node metastases. Patients with chromophobe RCC are significantly more likely to develop liver metastases. As the nuclear grade increased, there was also a significantly increased tendency for clear-cell RCC to metastasize to the lungs. Patients with sarcomatoid RCC had a higher rate of metastasis, with a significantly higher probability of metastasis to the bone and lungs, than those with all three histological subtypes did. Conclusions: Histological subtype, nuclear grade, and sarcomatoid differentiation were significant predictors of metastasis in patients with RCC.

Comparison of Metastatic Patterns Among Neuroendocrine Tumors, Neuroendocrine Carcinomas, and Nonneuroendocrine Carcinomas of Various Primary Organs.

BACKGROUND: Both neuroendocrine tumors (NETs) and neuroendocrine carcinomas (NECs) exhibit neuroendocrine differentiation and are classified as neuroendocrine neoplasms (NENs). NECs and nonneuroendocrine neoplasms (non-NENs), such as adenocarcinoma, have similar mutational profiles. The purpose of this study was to identify differences in metastatic patterns and to identify the key factor causing these differences by simultaneously comparing the metastatic patterns of NETs, NECs and non-NENs from various primary organs. METHODS: We retrieved data for 4,223 patients with NENs and 41,637 patients with non-NENs arising at various primary sites from an institutional database and then compared NET, NEC, and non-NEN metastatic patterns. RESULTS: NETs and NECs showed generally similar metastatic patterns. Most NEN patients had a higher liver organotrophic metastasis rate, lower lung organotrophic metastasis rate, and lower pleural/peritoneal organotrophic metastasis rate than non-NEN patients. Some differences were characteristics of specific organs. Some of these site-specific differences were not caused by NENs but by non-NENs, including a higher bone organotrophic metastasis rate for medullary thyroid carcinoma and a lower bone organotrophic metastasis rate for pulmonary NEN. Other differences were probably caused by NENs, including a higher bone organotrophic metastasis rate for colorectal NETs. Uterine cervical NEC showed unique patterns of metastasis compared to NEN from other sites. CONCLUSION: Significant differences between the metastatic patterns of NENs and non-NENs were detected. The multigene program that causes neuroendocrine differentiation might be associated with organotropic metastasis.

Patterns of Extrathoracic Metastasis in Lung Cancer Patients.

Metastasis is a major cause of death in lung cancer patients. Therefore, a deeper understanding of the metastatic mechanisms is important for developing better management strategies for lung cancer patients. This study evaluated the patterns of extrathoracic metastases in lung cancer. We retrieved data for 25,103 lung cancer patients from an institutional database and then evaluated the impacts of clinicopathologic factors on metastasis patterns. We found that 36.5% of patients had extrathoracic metastasis. Younger patients had a significantly higher extrathoracic metastasis rate in most histologic subtypes. Metastases to the bone (58.3%), central nervous system (CNS) (44.3%), liver (26.6%) and adrenal gland (18.3%) accounted for 85.5% of all extrathoracic metastases. Patients with nonmucinous adenocarcinoma had significantly higher bone metastasis rate. Patients with small cell carcinoma and large cell neuroendocrine carcinoma (LCNEC) had significantly higher liver metastasis rates. Further, patients with LCNEC also had a significantly lower bone metastasis rate, and patients with squamous cell carcinoma had a significantly lower CNS metastasis rate. Patients with multiple cancers had similar patterns of metastasis compared to patients with only lung cancer. In conclusion, different histologic subtypes of lung cancer have different metastatic patterns. Our study might help clinicians decide on follow-up strategies.

Neuroendocrine Carcinomas of the Uterine Cervix, Endometrium, and Ovary Show Higher Tendencies for Bone, Brain, and Liver Organotrophic Metastases.

Neuroendocrine carcinoma (NEC) of the female genital tract is a rare and aggressive subtype of cancer that is still poorly understood. Several recent studies reported that pulmonary and gastroenteropancreatic neuroendocrine neoplasms show significantly different patterns of metastasis compared to non-NECs of the same primary sites. The aim of this study was to evaluate the metastatic patterns of gynecologic NECs and to compare the metastatic patterns of NECs and non-NECs of the same primary sites. We retrieved and analyzed cervical, endometrial, and ovarian NEC cases from the Surveillance, Epidemiology, and End Results (SEER) database. To validate the results, we also retrieved and analyzed cervical NEC cases from an institutional database. Uterine cervical NEC was the most common NEC. The overall metastatic rate was significantly higher in the NEC group than in the non-NEC group for all three primary sites. All cervical, endometrial, and ovarian NECs showed a higher tendency for bone, brain, and liver organotrophic metastasis than non-NECs of the same primary sites. We demonstrated that gynecologic NECs show significantly different metastatic patterns compared to non-NECs of the same primary sites. These findings might help clinicians to better manage patients with gynecologic NECs.

Characterization of Poorly Cohesive and Signet Ring Cell Carcinomas and Identification of PTPRM as a Diagnostic Marker.

Background and aims. Signet ring cell (SRC) and poorly cohesive (PC) gastric carcinomas are morphologically similar but exhibit different biological behavior. We compared the clinical and molecular characteristics of SRC and PC carcinomas. Methods. Diffuse-type gastric cancer (GC) cases were classified into SRC carcinomas (>90% of SRCs), PC carcinomas (<10% of SRCs), and combined PC/SRC carcinomas (≤90% but ≥10% of SRCs). The gene expression patterns in SRC and PC carcinomas were examined by transcriptome and protein immunohistochemistry analyses, and diagnostic and prognostic biomarkers were identified. Results. SRC and PC carcinomas showed significantly different clinical behaviors but shared common RNA expression patterns. PC carcinomas showed an increased expression of genes related to cancer progression. Among genes differentially expressed between PC and SRC carcinomas, protein tyrosine phosphatase receptor type M (PTPRM) was overexpressed in PC and related to unfavorable clinical factors. Conclusion. We found that PC and SRC carcinomas had distinct clinical characteristics and should be classified as different carcinoma types. PTPRM was identified as a potential diagnostic and prognostic biomarker for PC carcinomas and could represent a potential therapeutic target.

mRNA expressions of androgen receptor and its variants in matched hormone-sensitive and castration-resistant prostate cancer.

Objectives: Androgen receptor splice variants (AR-Vs), especially androgen receptor splice variant 7 (AR-V7), are considered as important factors in developing castration-resistance of prostate cancer and also as candidate predictive factors. Our aim was to evaluate changes in the mRNA expression of full-length AR (AR-FL) and AR-Vs in the primary prostate cancers from the same patients before and after ADT.Methods: We compared morphologic differences and evaluated AR-FL, AR-V7, AR-V4, ARv567es, AR-V3 and AR8 mRNA expression in matched samples of primary hormone-sensitive and castration-resistant prostate cancer (CRPC) from 19 patients.Results: mRNA expression of AR-FL, AR-V7, ARv567es and AR-V3 was present in hormone sensitive prostate cancer (HSPC) and was significantly increased in CRPC in 81.2% (13/16). There were strong positive correlations between AR-FL and AR-V7 (r = 0.93, p < .001), ARv567es (r = 0.72, p < .001) and AR-V3 (r = 0.81, p < .001) mRNA expression. AR-V7/AR-FL ratio was more significantly (>30%) increased after ADT in 25% (4/16) of the patients, who showed significantly (p < .001) worse overall survival. Neuroendocrine differentiation was seen in one patient (5.3%) and the Gleason score was increased in 10 (52.6%) patients.Conclusion: We demonstrated that the expression of AR-V7 is present at low levels in HSPC and is increased in CRPC and the increase is an active process possibly related to aggressive clinical course.

Interobserver Reproducibility of PD-L1 Biomarker in Non-small Cell Lung Cancer: A Multi-Institutional Study by 27 Pathologists.

BACKGROUND: Assessment of programmed cell death-ligand 1 (PD-L1) immunohistochemical staining is used for treatment decisions in non-small cell lung cancer (NSCLC) regarding use of PD-L1/programmed cell death protein 1 (PD-1) immunotherapy. The reliability of the PD-L1 22C3 pharmDx assay is critical in guiding clinical practice. The Cardiopulmonary Pathology Study Group of the Korean Society of Pathologists investigated the interobserver reproducibility of PD-L1 staining with 22C3 pharmDx in NSCLC samples. METHODS: Twenty-seven pathologists individually assessed the tumor proportion score (TPS) for 107 NSCLC samples. Each case was divided into three levels based on TPS: <1%, 1%-49%, and ≥50%. RESULTS: The intraclass correlation coefficient for TPS was 0.902±0.058. Weighted κ coefficient for 3-step assessment was 0.748±0.093. The κ coefficients for 1% and 50% cut-offs were 0.633 and 0.834, respectively. There was a significant association between interobserver reproducibility and experience (formal PD-L1 training, more experience for PD-L1 assessment, and longer practice duration on surgical pathology), histologic subtype, and specimen type. CONCLUSIONS: Our results indicate that PD-L1 immunohistochemical staining provides a reproducible basis for decisions on anti-PD-1 therapy in NSCLC.

Molecular changes in solitary fibrous tumor progression.

Solitary fibrous tumors (SFTs) are NAB2-STAT6 fusion-associated neoplasms. There are several subtypes of NAB2-STAT6 fusions, but their clinical significances are still unclear. Moreover, the mechanisms of malignant progression are also poorly understood. In this study, using 91 SFT cases, we examined whether fusion variants are associated with clinicopathological parameters and also investigated the molecular mechanism of malignant transformation using whole-exome sequencing. We detected variant 1b (NAB2ex4-STAT6ex2) in 51/91 (56%) cases and variants 2a/2b (NAB2ex6-STAT6ex16/17) in 17/91 (19%) cases. The NAB2-STAT6 fusion variant types were significantly associated with their primary site (P < 0.001). In addition, a TERT promoter mutation was detected in 7/73 (10%) cases, and it showed a significant association with malignant SFTs (P = 0.003). To identify molecular changes during malignant progression, we selected an index patient to obtain parallel tissue samples from the primary and metastatic tumors. In the metastatic tissue, 10 unique molecular alterations, including those in TP53 and APAF1, were detected. In vitro functional experiments showed that APAF1 depletion increased the tumor potency of cells expressing NAB2-STAT6 fusion protein under treatment with staurosporine. We found that TP53 immunopositivity (P = 0.006) and loss of APAF1 immunoreactivity (P < 0.001) were significantly associated with malignant SFTs. Our study suggests that dysfunction of TP53 and APAF1 leads to impaired apoptotic function, and eventually contributes toward malignant SFT transformation. KEY MESSAGES: We firstly found that the TERT promoter mutation was strongly associated with malignant SFTs (P = 0.003) and the representative 1b (NAB2ex4-STAT6ex2) or 2a (NAB2ex6-STAT6ex16) fusion variants similarly contribute to tumorigenicity. We also found that TP53 immunopositivity (P = 0.006) and loss of APAF1 immunoreactivity (P < 0.001) were significantly associated with malignant SFTs. Our study suggests that dysfunction of TP53 and APAF1 leads to impaired apoptotic function, and eventually contributes toward malignant SFT transformation.

Co-expression of MDM2 and CDK4 in transformed human mesenchymal stem cells causes high-grade sarcoma with a dedifferentiated liposarcoma-like morphology.

Amplification and overexpression of MDM2 and CDK4 are well-known diagnostic criteria for well-differentiated liposarcoma (WDLPS)/dedifferentiated liposarcoma (DDLPS). Although it was reported that the depletion of MDM2 or CDK4 decreased proliferation in DDLPS cell lines, whether MDM2 and CDK4 induce WDLPS/DDLPS tumorigenesis remains unclear. We examined whether MDM2 and/or CDK4 cause WDLPS/DDLPS, using two types of transformed human bone marrow stem cells (BMSCs), 2H and 5H, with five oncogenic hits (overexpression of hTERT, TP53 degradation, RB inactivation, c-MYC stabilization, and overexpression of HRASv12). In vitro functional experiments revealed that the co-overexpression of MDM2 and CDK4 plays a key role in tumorigenesis by increasing cell growth and migration and inhibiting adipogenic differentiation potency when compared with the sole expression of MDM2 or CDK4. Using mouse xenograft models, we found that the co-overexpression of MDM2 and CDK4 in 5H cells with five additional oncogenic mutations can cause proliferative sarcoma with a DDLPS-like morphology in vivo. Our results suggest that the co-overexpression of MDM2 and CDK4, along with multiple genetic factors, increases the tendency for high-grade sarcoma with a DDLPS-like morphology in transformed human BMSCs by accelerating their growth and migration and blocking their adipogenic potential.

Status of programmed death-ligand 1 expression in sarcomas.

BACKGROUND: Sarcomas are challenging to study because of their rarity and histomorphological complexity. PD1 and PD-L1 inhibitors showed a promising anti-tumor effect in solid tumors, where a relationship between PD-L1 expression and the objective response has been evidenced. METHODS: In this study, we examined PD-L1 expression in 16 bone and soft tissue sarcoma cell lines of 11 different subtypes by means of western blot, flow cytometry and immunocytochemistry, and in 230 FFPE patient-derived tumor tissues by means of immunohistochemistry using three different antibody clones. The association between PD-L1 expression and clinicopathological features was evaluated. RESULTS: We demonstrated that PD-L1 protein is highly expressed in pleomorphic rhabdomyosarcoma, fibrosarcoma, and dedifferentiated liposarcoma (DDLPS) cell lines. From the tissue microarray, undifferentiated pleomorphic sarcoma showed ≥ 1% immunoreactivity in 20%, 17.6%, and 16.3% of the cases with PD-L1 22C3, SP263, and SP142 antibodies, respectively. In whole sections stained with a PD-L1 22C3 antibody, DDLPS showed ≥ 1% immunoreactivity in 21.9% of the cases. In DDLPS group, cases with ≥ 1% PD-L1 expression showed statistically significantly worse recurrence-free survival (P = 0.027) and overall survival (P = 0.017) rates. Upon interferon-gamma treatment, the mRNA expression levels of PD-L1 were elevated in the HS-RMS-1, LIPO-224B, MLS1765, RH30, and RH41 cell lines. CONCLUSIONS: We found that the expression of PD-L1 in sarcoma differs depending on the histologic subtype and the PD-L1 antibody clones. These results may serve as primary data for the selection of appropriate patients when applying PD1/PD-L1 inhibitor therapy in sarcoma.

Secondary Aneurysmal Bone Cyst in a Craniofacial Fibrous Dysplasia: Case Report.

Aneurysmal bone cyst (ABC) is a rare non-neoplastic bone lesion that involves mostly the long bones and vertebrae and may occur very rarely in the craniofacial bones. ABCs may occur as secondary bony pathologies in association with various benign and malignant bone tumors and with fibrous dysplasia (FD). FD is a common non-neoplastic bony pathology mostly affecting craniofacial bones. Secondary ABC occurring in craniofacial FD is extremely rare, with only approximately 20 cases reported in the literature to date. Here, we report on a case of secondary ABC in a 25-year-old woman who has had a craniofacial deformity for over 10 years and who presented to us with a rapidly growing painful pulsatile mass in the right frontal region that began over 2 months prior to admission. On thorough examination of computed tomography and magnetic resonance imaging brain scans taken at two-month interval, an aggressive, rapidly enlarging ABC, arising from the right frontal FD, was diagnosed. The patient underwent preoperative embolization followed by gross total resection of the ABC and cranioplasty. The 6-month follow up showed no recurrence of the ABC, nor was any progression of the FD noticed.

Pancreatic Ductal Adenocarcinoma: Rim Enhancement at MR Imaging Predicts Prognosis after Curative Resection.

Purpose To identify features at preoperative magnetic resonance (MR) imaging that could predict favorable prognosis after curative resection of pancreatic ductal adenocarcinoma (PDAC). Materials and Methods From January 2009 to December 2014, this retrospective study included 143 patients with surgically resected (ie, R0) PDAC who underwent preoperative MR imaging within 1 month before surgery. Clinical-pathologic and MR imaging findings for predicting disease-free survival (DFS) and overall survival (OS) were identified by using a Cox proportional hazards model. Important MR imaging features were compared with clinical-pathologic findings. Results Tumor size at histopathologic analysis was associated with both DFS and OS (hazard ratio per centimeter, 1.37; 95% confidence interval: 1.15, 1.63; P < .001 and hazard ratio, 1.44; 95% confidence interval: 1.20, 1.73; P < .001, respectively). Rim enhancement at dynamic contrast material-enhanced MR imaging was associated with significantly worse DFS and OS (hazard ratio, 1.72; 95% confidence interval: 1.05, 2.82; P = .030 and hazard ratio, 2.27; 95% confidence interval: 1.39, 3.69; P = .001, respectively). Diffusion-weighted imaging parameters, including diffusion restriction and apparent diffusion coefficient value, did not predict DFS or OS after resection of PDAC (all P > .05). Rim-enhancing lesions had more aggressive histologic tumor grades, less frequent remaining acini, and more frequent necrosis within the tumor compared with non-rim-enhancing pancreatic lesions (P = .002, P = .008, and P < .001, respectively). Conclusion Greater tumor size and rim enhancement were associated with lower DFS and OS rates after attempted curative resection of PDAC.

Peritumoral lymphoid cuff correlates well with lymph node enlargement in gastrointestinal schwannomas.

BACKGROUND/AIMS: To determine the incidence of regional lymphadenopathy in gastrointestinal (GI) schwannoma and to evaluate the relationship between peritumoral lymphoid cuff and lymphadenopathy. METHODS: We queried 118 GI tract schwannomas and reviewed radiologic findings, intraoperative findings, and electronic medical records of all cases for enlarged regional lymph nodes. RESULTS: Location of tumors included 85 gastric (72%), 11 colonic (9.3%), 7 esophageal (5.9%), 3 pancreatic (2.5%), 1 hepatic (0.8%), and 11 mesenteric (9.3%). The size of the tumors ranged from 0.2 to 11 cm (mean 3.8 cm). Histologically, 70.3% showed a peritumoral lymphoid cuff ranging in thickness from 0.3 to 6 mm (mean 1.6 mm). The peritumoral lymphoid cuff was significantly more frequent in gastric schwannomas (78.8%) followed by colonic (72.7%), esophageal (57.1%) and rare in other locations (p = 0.001). Of the 106 cases for which clinical or radiologic data was available for, 76 cases (71.7%) showed regional lymphadenopathy. The presence of peritumoral lymphoid cuff showed significant correlation with regional lymphadenopathy (p < 0.001) and the size of enlarged lymph nodes (p = 0.002). CONCLUSIONS: A peritumoral lymphoid cuff is frequently seen in GI tract schwannomas and correlates well with regional lymphadenopathy. However, in a significant subset (29.7%), a lymphoid cuff was not present warranting continued need for caution in the preoperative radiologic and postoperative pathologic diagnoses.

Unforeseen clonal evolution of tumor cell population in recurrent and metastatic dermatofibrosarcoma protuberans.

Dermatofibrosarcoma protuberans (DFSP) is a very rare soft tissue sarcoma, generally of low-grade malignancy. DFSP is locally aggressive with a high recurrence rate, but metastasis occurs rarely. To investigate the mechanism of metastasis in DFSP, we analyzed the whole exome sequencing data of serial tumor samples obtained from a patient who had a 10-year history of recurrent and metastatic DFSP. Tracking various genomic alterations, namely somatic mutations, copy number variations, and chromosomal rearrangements, we observed a dramatic change in tumor cell population during the occurrence of metastasis in this DFSP case. The new subclone that emerged in metastatic DFSP harbored a completely different set of somatic mutations and new focal amplifications, which had not been observed in the primary clone before metastasis. The COL1A1-PDGFB fusion, characteristic of DFSP, was found in all of the serial samples. Moreover, the break position on the fusion gene was identical in all samples. Based on these observations, we suggest a clonal evolution model to explain the mechanism underlying metastasis in DFSP and identified several candidate target genes responsible for metastatic DFSP by utilizing The Cancer Genome Atlas database. This is the first study to observe clonal evolution in metastatic DFSP and provide insight for a possible therapeutic strategy for imatinib-resistant or metastatic DFSP.

Comparison and evaluation of risk factors for meningeal, pleural, and extrapleural solitary fibrous tumors: A clinicopathological study of 92 cases confirmed by STAT6 immunohistochemical staining.

Solitary fibrous tumors (SFTs) are an uncommon type of mesenchymal tumors that are presumably fibroblastic in nature. SFTs are translocation-associated neoplasms that can be consistently diagnosed through the evaluation of NAB2/STAT6 gene fusion. Currently, SFTs have a different grading system and criteria according to their primary sites, and the differences and similarities in SFTs according to their primary sites are still poorly understood. Therefore, we compared SFTs according to their primary sites and histologic appearance, and validated the current grading system of SFTs. A total of 92 patients (with 15 meningeal, 40 pleural, and 37 extrapleural SFTs) were evaluated. The patients with pleural SFTs (mean age: 60.2 years) showed a significantly increased age at diagnosis. Tumors with hemangiopericytoma-predominant morphology had significantly higher grades in the evaluation of several risk factors such as cellularity (P<0.001), pleomorphism (P=0.001), and mitotic activity (P<0.001). Consequently, hemangiopericytoma (HPC)-predominant tumors had a significantly higher recurrence rate. The meningeal SFT group had significantly higher proportion of the HPC-predominant histologic phenotype compared with pleural or extrapleural SFTs (66.67% vs. 5.00% or 18.92%, respectively; P<0.001). Consequently, meningeal SFTs showed significantly higher recurrence rates compared with pleural or extrapleural SFTs (33.33% vs. 12.50% or 2.70%, respectively; P=0.009). Regarding the evaluation of risk factors, a tumor size ≥10cm (P=0.017), a mitotic index ≥4/10 high power fields (HPFs) (P=0.001), high tumor cellularity (P=0.003), high nuclear pleomorphism (P=0.005), and tumor necrosis (P=0.004) were associated with both recurrence and disease-specific mortality. Upon evaluation of the usefulness of the criteria using previously described factors, the predictive model was on the borderline of validation. Of the five factors indicated in the log rank test, only a mitotic index ≥4/10 HPFs remained a significant factor in the multivariate Cox model.