CD30 expression in an emerging group of mesenchymal spindle cell neoplasms with ALK fusion detected by flow cytometry and immunohistochemistry.

An emerging group of spindle cell neoplasms harboring fusions involving NTRK or non-NTRK kinase genes often share characteristic S100 and/or CD34 expression; however, the diagnostic utility of immunohistochemical stains is not well established in this family owing to their lack of specificity. Recently, CD30 expression in spindle cell neoplasms with kinase gene fusions, such as NTRK, BRAF, RAF1, and RET, has been increasingly identified. We herein report a 10-year-old girl with high-grade spindle cell sarcoma of the neck. Prior to histopathological evaluation, flow cytometry (FCM) analysis and touch smear cytology of the tumor tissue revealed CD34+ and dimCD30+ spindle cell populations. Histopathologically, the case was characterized by monomorphic spindle-shaped cytomorphology with CD30, S100, and CD34 positivity and harbored close similarities with spindle cell neoplasms with NTRK or non-NTRK gene fusions. Subsequently, a comprehensive next-generation sequencing sarcoma panel identified a rare PLEKHH2::ALK fusion, and a diagnosis of ALK-rearranged spindle cell neoplasm was made. The patient showed significant tumor response to single-agent treatment with alectinib, an ALK-tyrosine kinase inhibitor. This case supports that CD30 is expressed in an ALK-rearranged mesenchymal neoplasm. The benefit of the early detection of CD30 expression by FCM for a prompt diagnosis and treatment is highlighted in the context of an aggressive clinical course. This case represents a learning experience regarding the need to the check the status of CD30 expression in these tumors and suggests the potential clinical benefits of CD30-targeted therapy.

A case with multiple nodules and mucosal oedema of the trachea and both bronchi induced by IgG4-related disease.

BACKGROUND: IgG4-related disease is a systemic fibroinflammatory disease that is mainly seen in older men, and involves multiple organs, such as the pancreas and lungs. However, 75% of patients with IgG4-related lung disease are asymptomatic (if they are symptomatic, they mainly complain of nasal congestion, rhinorrhoea, chest pain, and cough) and are incidentally diagnosed through chest computed tomograph. Although, nodules in the airway and bronchial wall thickening are criteria for diagnosis, it is important that nodules have been reported in peripheral airways in several cases and rarely in the central airway. CASE PRESENTATION: A 74-year-old woman previously diagnosed with Mikulicz's disease presented with swelling of the eyelid margin on both sides and visual disturbances. Computed tomography revealed extensive multiple nodules and mucosal oedema of the trachea and both bronchi. On flexible bronchoscopy under local anaesthesia, extensive lesions were observed from the middle of the trachea to the carina, extending into both segmental bronchi. The nodules were continuous with the normal respiratory tract mucosa, and the surfaces were smooth with minimal neovascularisation. Due to the solid nature of the lesion, obtaining an adequate amount of specimen was challenging. Therefore, we used a 1.9 mm cryoprobe under intubation, resulting in minimal bleeding. Subsequently, the patient was diagnosed with IgG4-related lung disease. CONCLUSIONS: The present case is very rare because of the presence of multiple nodules, severe mucosal edema of the central airway and the absence of mediastinal lymphadenopathy, ground glass nodules, and lung masses. Therefore, it is important to consider differential diagnoses. Thus, we emphasise the importance of endobronchial cryobiopsy for obtaining an adequate number of tissue specimens in such cases to establish a definitive pathological diagnosis.

[A Case of Undifferentiated Sarcoma of the Liver in an Adult Treated with Right Hepatectomy Followed by Adjuvant Chemotherapy].

Undifferentiated sarcoma of the liver is rare, especially in adults, and is an aggressive malignancy that originates from the primary mesenchymal tissues. A 53-year-old man was referred to our hospital for further evaluation of a low-grade fever. Contrast-enhanced CT revealed an 18-cm tumor in the right lobe of the liver. The tumor was characterized by low-density areas suspected of cystic components, a high-density area suspected of hemorrhage, and contrast enhancement in the thickened marginal and internal septa. MRI revealed a high-intensity tumor with a heterogeneous structure on T2-weighted images. Angiosarcoma of the liver with intratumoral hemorrhage was suspected, and right hepatectomy was performed. The pathological diagnosis was an undifferentiated sarcoma based on the presence of undifferentiated mesenchymal tumor cells with a stellate to spindle-shaped pleomorphism. Following a multidisciplinary discussion, 4 courses of the AI regimen (doxorubicin and ifosfamide)were administered as adjuvant chemotherapy, and no recurrence was confirmed at 2 years and 6 months follow-up. Our case suggests that radical resection followed by adjuvant chemotherapy may contribute to a favorable prognosis for undifferentiated sarcoma of the liver.

Mucous Gland Adenoma of the Lung: A Neoplastic Counterpart of Mucinous Bronchial Glands.

Mucous gland adenoma (MGA) is a rare benign tumor that usually arises in the proximal airway and consists of mucus-secreting cells resembling bronchial glands. Here, we report 2 cases of MGAs and describe their morphologic, immunohistochemical, and molecular profiles in comparison with 19 pulmonary tumors of 5 other histologic types with mucinous cells (invasive mucinous adenocarcinoma, mucoepidermoid carcinoma, mixed squamous cell and glandular papilloma, bronchiolar adenoma/ciliated muconodular papillary tumor, and sialadenoma papilliferum). Two MGAs were found in 1 male patient and 1 female patient, located in the bronchus and trachea, respectively. One MGA was examined by RNA sequencing, and no putative driver mutations (including BRAF, KRAS, and AKT1 mutations) or gene fusions were identified. In another case of MGA, V600E mutations of BRAF and E17K mutations of AKT1 were not detected by allele-specific real-time PCR or digital PCR, respectively. However, a gene expression analysis revealed that the MGA presented a specific RNA expression profile with multiple genes enriched in the salivary gland. The gene expression of NKX3.1 was significantly higher in the MGA case in comparison to normal control lungs (P < .001). We then examined NKX3.1 immunohistochemistry for 2 MGAs and 19 tumors of 5 other histologic types. NKX3.1 was positive in MGA (2/2, 100%), whereas all constituent cells, including mucinous cells, were negative for NKX3.1 in other histologic types (0%, 0/19). In normal lung tissue, NKX3.1 was positive for mucinous acinar cells of the bronchial glands. In conclusion, the gene expression profile, taken together with the histologic similarity between MGA and bronchial glands, and the preferred location of the tumors (proximal airways with submucosal glands) suggest that MGA is a neoplastic counterpart of mucinous bronchial glands. NKX3.1 immunohistochemistry can be a sensitive and specific ancillary marker that distinguishes MGA from other histologic mimics.

[Diffuse large B-cell lymphoma expressing high-level glyceraldehyde 3-phosphate dehydrogenase complicated with hypoglycemia].

A 69-year-old male patient was referred to our hospital for further examination of hypoglycemia, splenomegaly, and para-aortic lymphadenopathy. The patient was diagnosed with diffuse large B-cell lymphoma (DLBCL) by para-aortic lymph node biopsy. Hypoglycemia was refractory to glucose supplementation but improved shortly after chemotherapy. This situation suggested that hypoglycemia was caused by lymphoma. We compared the expression levels of glyceraldehyde 3-phosphate dehydrogenase, a glycolytic enzyme whose expression is positively correlated with the glycolytic activity of cells, between the current case and two cases of DLBCL without hypoglycemia to explore the possibility that hypoglycemia was due to intense glucose consumption by lymphoma cells through their high glycolytic activity. Results revealed substantially higher expression levels of glyceraldehyde 3-phosphate dehydrogenase in the current case than in DLBCL without hypoglycemia, suggesting that the glycolytic pathway was enhanced in the current case. These results implied that intense glucose consumption by lymphoma cells through their high glycolytic activity causes hypoglycemia.

Diagnostic utility of programmed cell death ligand 1 (clone SP142) in mediastinal composite lymphoma: A report of two cases.

Composite lymphoma is a well-known diagnostic entity exhibiting the synchronous occurrence of two or more distinct types of lymphomas in the same specimen. Here we report two patients, a 14-year-old female (Case 1) and a 45-year-old male (Case 2), with mediastinal composite lymphoma, comprising nodular sclerosis classic Hodgkin lymphoma (NSCHL) and primary mediastinal large B-cell lymphoma (PMBL). Both patients had a mediastinal mass, and manifested two different histologic components in the same biopsy, one characteristic of NSCHL and the other PMBL. The NSCHL areas included Hodgkin and Reed-Sternberg (HRS) cells with typical immunophenotypic features (CD30-positive and CD20-negative), whereas the sheets of large tumor cells characteristic of PMBL were strongly and uniformly CD20-positive. Interestingly, although both cases showed neoplastic PD-L1 (nPD-L1) positivity on the HRS cells of NSCHL, they differed regarding nPD-L1 expression on the PMBL tumor cells. In Case 1, the nPD-L1-negative PMBL component was anatomically situated outside the NSCHL lesion. On the other hand, in Case 2, the nPD-L1-positive PMBL component was characterized by transitional or continuous areas with the NSCHL component. These findings suggested that nPD-L1 expression may define two subtypes of PMBL that are more similar to or distinct from classic Hodgkin lymphoma.

Syncytial variant of classic Hodgkin lymphoma: Four cases diagnosed with the aid of CD274/programmed cell death ligand 1 immunohistochemistry.

Although several reports have highlighted neoplastic PD-L1 (nPD-L1) expression in classic Hodgkin lymphoma (CHL), some have addressed associations between its expression and detailed histopathologic features. Here we describe four cases of syncytial variant of CHL (SV-CHL), with and without Epstein-Barr virus (EBV) association, and highlight the diagnostic utility of PD-L1 (clone SP142) immunohistochemistry. The patients were a 61-year-old male, 45-year-old male, 85-year-old female, and 89-year-old female. All presented with cervical or axillary lymphadenopathy, which on biopsy had the established histopathologic features of SV-CHL with a biphasic pattern of cohesive sheets of large tumor cells and typically scattered distribution of Hodgkin and Reed-Stenberg (HRS) cells. These tumor cells showed identical immunophenotypic findings for CD15, CD30, Fascin, PAX5, OCT2, BOB1 and EBV harboring, regardless of location. The exception was absent or decreased expression of nPD-L1 from tumor cells in the confluent sheets, contrasting with HRS cell positivity in typical areas of CHL. These findings offer the first suggestion of possible downregulation of nPD-L1 expression in association with the histopathologic progression of CHL. The results may be relevant for recognizing 'confluent' sheets in the diagnostic workup for SV-CHL.

HNF6 and HNF4α expression in adenocarcinomas of the liver, pancreaticobiliary tract, and gastrointestinal tract: an immunohistochemical study of 480 adenocarcinomas of the digestive system.

Hepatocyte nuclear factors (HNF) 6 and 4α are master transcriptional regulators of development and maintenance of the liver and pancreaticobiliary tract in mice and humans. However, little is known about the prevalence of HNF6 and HNF4α expression in carcinomas of the hepatobiliary tract and pancreas. We aimed to reveal the diagnostic utility of HNF6 and HNF4α immunolabelling in adenocarcinomas of these organs. We investigated HNF6 and HNF4α expression by immunohistochemistry using a total of 480 adenocarcinomas of the digestive system, including 282 of the hepatobiliary tract and pancreas and 198 of the gastrointestinal tract. HNF6 expression was primarily restricted to intrahepatic cholangiocarcinomas (CCs) (63%, n=80) and gallbladder adenocarcinomas (43%, n=88), among others. Notably, small duct intrahepatic CCs almost invariably expressed HNF6 (90%, n=42), showing stark contrast to a low prevalence in large duct intrahepatic CCs (10%, n=21; p<0.0001). HNF6 expression was infrequent in extrahepatic CCs (9%, n=55) and pancreatic ductal adenocarcinomas (7%, n=58), and it was rare in adenocarcinomas of the gastrointestinal tract [oesophagus/oesophagogastric junction (EGJ) (2%, n=45), stomach (2%, n=86), duodenum (0%, n=25), and colorectum (0%, n=42)]. In contrast, HNF4α was widely expressed among adenocarcinomas of the digestive system, including intrahepatic CCs (88%), extrahepatic CCs (94%), adenocarcinomas of the gallbladder (98%), pancreas (98%), oesophagus/EGJ (96%), stomach (98%), duodenum (80%), and colorectum (100%). HNF6 was frequently expressed in and almost restricted to intrahepatic CCs of small duct type and gallbladder adenocarcinomas, while HNF4α was expressed throughout adenocarcinomas of the digestive system. HNF6 immunolabelling may be useful in distinguishing small duct intrahepatic CCs from other types of CC as well as metastatic gastrointestinal adenocarcinomas.

Phase-contrast visualization of human tissues using superimposed wavefront imaging of diffraction-enhanced x-rays.

BACKGROUND: Phase-contrast computed tomography (CT) using high-brilliance, synchrotron-generated x-rays enable three-dimensional (3D) visualization of microanatomical structures within biological specimens, offering exceptionally high-contrast images of soft tissues. Traditional methods for phase-contrast CT; however, necessitate a gap between the subject and the x-ray camera, compromising spatial resolution due to penumbral blurring. Our newly developed technique, Superimposed Wavefront Imaging of Diffraction-enhanced x-rays (SWIDeX), leverages a Laue-case Si angle analyzer affixed to a scintillator to convert x-rays to visible light, capturing second-order differential phase contrast images and effectively eliminating the distance to the x-ray camera. This innovation achieves superior spatial resolution over conventional methods. PURPOSE: In this paper, the imaging principle and CT reconstruction algorithm based on SWIDeX are presented in detail and compared with conventional analyzer-based imaging (ABI). It also shows the physical setup of SWIDeX that provides the resolution preserving second-order differential images for reconstruction. We compare the spatial resolution and the sensitivity of SWIDeX to conventional ABI. METHODS: To demonstrate high-spatial resolution achievable by SWIDeX, the internal structures of four human tissues-ductal carcinoma in situ, normal stomach, normal pancreas, and intraductal papillary mucinous neoplasm of the pancreas-were visualized using an imaging system configured at the Photon Factory's BL14B beamline under the High Energy Accelerator Research Organization (KEK). Each tissue was thinly sliced after imaging, stained with hematoxylin and eosin (H&E) for conventional microscope-based pathology. RESULTS: A comparison of SWIDeX-CT and pathological images visually demonstrates the effectiveness of SWIDeX-CT for biological tissue imaging. SWIDeX could generate clearer 3D images than existing analyzer-based phase-contrast methods and accurately delineate tissue structures, as validated against histopathological images. CONCLUSIONS: SWIDeX can visualize important 3D structures in biological soft tissue with high spatial resolution and can be an important tool for providing information between the disparate scales of clinical and pathological imaging.

Uniqueness of ductal carcinoma in situ of the breast concurrent with papilloma: implications from a detailed topographical and histopathological study of 50 cases treated by mastectomy and wide local excision.

AIMS: To clarify the diagnostic clues of ductal carcinomas in situ (DCIS) associated with papilloma and optimal clinical management of papilloma diagnosed on core needle biopsy (CNB). METHODS AND RESULTS: A total of 50 surgically resected cases were examined histopathologically and topographically. Thirty-nine cases (78%) spread in segmental fashion. Papilloma and DCIS were intermingled closely in 44 cases (88%), occupying the same areas in varying proportions from DCIS-predominant to papilloma-predominant. The two components occupied discrete areas and collided focally in six cases (12%). Most were non-high-grade. Cribriform and solid architectures with fibrovascular stroma were frequent. The cribriform pattern was unique, consisting of fused tubules separated by fibrovascular stroma. Intraductal myoepithelial cells were present to varying degrees in 40 cases (80%). In 38 cases (76%), points were identified where papilloma and DCIS coexisted or collided within a single lumen (CC point). Forty-eight cases (96%) had either intraductal myoepithelial cells or CC points, implying that DCIS and papilloma existed in the same duct system. Radiology showed segmental abnormalities in 83% of the available cases. CONCLUSIONS: Intraductal myoepithelial cells do not always guarantee benignity. Surgical resection is recommended for papilloma in CNB when radiology shows segmental abnormalities.

Expression of CD5 in salivary gland tumors: an ancillary marker for carcinoma showing thymus-like differentiation (CASTLE) of the major salivary gland.

Recently, cases of carcinoma showing thymus-like differentiation (CASTLE) occurring in major salivary glands have been identified. To assess the diagnostic value of CD5 immunohistochemistry in distinguishing salivary CASTLE from other types of salivary gland tumors, we evaluated CD5 expression in 109 salivary gland tumors, encompassing 23 different histological types, including salivary CASTLE. In addition, we reviewed 10 previously reported cases of salivary CASTLE. Most salivary CASTLE cases (10/11, 91%) showed strong CD5 expression. In contrast, 104 of 108 (96%) non-salivary CASTLE tumors were negative for CD5, while the remaining four tumors (3.7%), all of which were histologically Warthin tumors, showed focal positivity for CD5 with weak to moderate intensity. In conclusion, the findings in this study support the potential use of CD5 immunohistochemistry for distinguishing salivary CASTLE from other histological types of salivary gland tumors. Aberrant CD5 expression in this tumor may be linked to the tumor microenvironment.

RET finger protein expression is associated with prognosis in lung cancer with epidermal growth factor receptor mutations.

The RET finger protein (RFP) is a transcription factor belonging to the TRIM (tripartite motif) superfamily of proteins. RFP is expressed in a variety of human and rodent tumor cell lines and in several kinds of human cancer. Expression of RFP is associated with prognosis of colon and endometrial cancers. In the present study, we evaluated the expression of RFP in lung cancer and assessed its clinical significance. Tissue microarrays were constructed from 108 cases of lung cancer, and the sections were analyzed for RFP expression by immunohistochemistry. RFP expression was detected in the nucleus in 66.7% of lung cancer tissues examined. RFP expression was statistically significantly associated with thyroid transcription factor 1 (TTF-1) expression (P= 0.028). However, no significant association was observed between RFP expression and other clinicopathological or genetic factors, including epidermal growth factor receptor (EGFR) mutations. Interestingly, we found that RFP expression correlated with poor prognosis in patients with EGFR mutations (P= 0.032). Our results suggest that RFP has a role in mutated EGFR signaling and that RFP status may be a prognostic factor for lung cancer with EGFR mutations.

Clinical heterogeneity between two subgroups of patients with idiopathic orbital inflammation.

OBJECTIVE: Idiopathic orbital inflammation (IOI) is a group of orbital inflammatory diseases of unknown etiopathogenesis. We investigated whether patients with IOI have clinical heterogeneity based on the presence (typical group) or absence (atypical group) of a unique onset that periocular inflammatory symptoms emerge suddenly but progress slowly. METHODS AND ANALYSIS: This retrospective cohort study included 195 patients diagnosed with IOI. We analysed the clinical data of patients, including the outcomes of corticosteroid treatment, in two subgroups stratified on the basis of the presence (130 patients) or absence (65 patients) of the unique onset. RESULTS: Patients in the typical group were significantly younger at disease onset than those in the atypical group (median age; 52 vs 65 years, p=0.002); had more ocular adnexa-specific lesions, namely, dacryoadenitis, myositis, scleritis and optic perineuritis (78% vs 45%, p=0.00001); and had significantly fewer associations with immune-mediated inflammatory diseases (4% vs 15%, p=0.004). Among 30/119 patients (25%) who were steroid refractory in the typical group, a long period of time from symptom onset to initiation of treatment was a significant steroid-refractory risk factor (OR: 16.7), whereas, among the 18/40 patients (45%) who were steroid refractory in the atypical group, intraconal diffuse lesions were a significant steroid-refractory risk factor (OR: 8.8). CONCLUSION: This cohort study suggests clinical heterogeneity between the two subgroups of patients with IOI.

Successful Resection of a Primary Dedifferentiated Tracheal Liposarcoma Causing Tracheal Stenosis.

A 68-year-old woman was admitted with a persistent cough and dyspnea that had persisted for 4 months prior. Chest computed tomography revealed a tumor protruding from the membranous portion of the trachea. She underwent tumor resection via rigid and flexible bronchoscopy to relieve the symptoms and obtain a diagnosis. After the procedure, she was diagnosed with tracheal liposarcoma. Three months after the procedure, she underwent complete surgical tumor resection. Liposarcoma is a mesenchymal tumor that usually develops in the extremities and the retroperitoneum. Tracheal liposarcoma is extremely rare. To the best of our knowledge, this is only the second reported case.

Primary central nervous system malignant lymphoma in a patient with rheumatoid arthritis receiving tocilizumab: illustrative case.

BACKGROUND: Although the risk of developing malignant lymphoma is higher in patients with rheumatoid arthritis (RA) than in the general population, primary central nervous system lymphoma (PCNSL) in patients with RA is extremely rare. In recent years, there has been concern that biological disease-modifying antirheumatic drugs (bDMARDs), widely administered to patients with RA, might increase the risk of cancer development. The authors report the first case of PCNSL in a patient with RA receiving the bDMARD tocilizumab. OBSERVATIONS: A 70-year-old man who was diagnosed with RA in 2010 was treated with low-dose methotrexate (MTX) from 2010 to 2015. Tocilizumab was commenced in 2012. In 2018, he developed gait disturbances, and gadolinium-enhanced magnetic resonance imaging showed multiple contrast-enhanced lesions in the basal ganglia and brain stem. Stereotactic brain biopsy led to the diagnosis of diffuse large B-cell lymphoma, and finally PCNSL was diagnosed. He was treated with five courses of MTX 3.5 g/m2, and his disease has been in remission for 34 months. LESSONS: Low-dose MTX and bDMARDs are associated with the concern of increased cancer risk in patients with RA. Because tocilizumab has been in use for a relatively short time, further accumulation of cases and careful follow-up are necessary.

Crystal optics simulations for delineation of the three-dimensional cellular nuclear distribution using analyzer-based refraction-contrast computed tomography.

Refraction-contrast computed tomography (RCT) using a refractive angle analyzer of Si perfect crystal can reconstruct the three-dimensional structure of biological soft tissue with contrast comparable to that of stained two-dimensional pathological images. However, the blurring of X-ray beam by the analyzer has prevented improvement of the spatial resolution of RCT, and the currently possible observation of tissue structure at a scale of approximately 20 µm provides only limited medical information. As in pathology, to differentiate between benign and malignant forms of cancer, it is necessary to observe the distribution of the cell nucleus, which is approximately 5-10 µm in diameter. In this study, based on the X-ray dynamical diffraction theory using the Takagi-Taupin equation, which calculates the propagation of X-ray energy in crystals, an analyzer crystal optical system depicting the distribution of cell nuclei was investigated by RCT imaging simulation experiments in terms of the thickness of the Laue-case analyzer, the camera pixel size and the difference in spatial resolution between the Bragg-case and Laue-case analyzers.

Thoracic SMARCA2-deficient But SMARCA4-preserved Tumors With Undifferentiated Morphology Combined With Claudin-4 Negativity.

Thoracic SMARCA4-deficient undifferentiated tumor (SMARCA4-UT) is a recently recognized tumor characterized by inactivation of SMARCA4, a SWItch/Sucrose NonFermentable chromatin remodeler, detectable by immunohistochemistry. SMARCA4-UT shows undifferentiated or rhabdoid morphology with claudin-4 negativity. However, thoracic undifferentiated tumors with the same histologic features as SMARCA4-UTs but a preserved SMARCA4 expression have so far been underrecognized. We herein report 3 cases of thoracic undifferentiated tumors with isolated loss of SMARCA2 but retained expression of SMARCA4 and SMARCB1. The present tumors were found in 2 men and 1 woman, 40 to 50 years old. All patients were heavy smokers (≥20 pack-years). The tumors were generally large masses located in the mediastinum, lung>chest wall, or lung and composed of relatively monotonous, round to epithelioid cells with variably rhabdoid cells. Immunohistochemically, the tumors showed claudin-4 negativity with variable expression of cytokeratin. All cases showed highly aggressive clinical behavior with overall survival of 2 to 10 months. These SMARCA2-deficient tumors with preserved SMARCA4 expression appeared to be clinicopathologically indistinguishable from SMARCA4-UTs, except for in their SMARCA4 status. This variant may expand the spectrum of SWItch/Sucrose NonFermentable-deficient undifferentiated tumors of the thoracic region beyond SMARCA4-UT.

The Diagnostic Utility of IDH2 R172 Immunohistochemistry in Tall Cell Carcinoma With Reversed Polarity of the Breast.

Tall cell carcinoma with reversed polarity (TCCRP) is a rare histologic type of low-grade breast cancer, consisting of tall columnar cells with reversed nuclear polarity and characterized by frequent IDH2 mutations. We herein report 3 cases of TCCRP with sequencing analyses of the IDH2 gene and immunohistochemical examination using monoclonal antibodies (11C8B1) against IDH2 R172. IDH2 R172 mutations were detected in all 3 resected tumors (R172S in 2 tumors and R172T in 1 tumor), and the presence of these mutations was confirmed by IDH2 R172 immunohistochemistry. Tumor cells of TCCRP showed strong and diffuse staining for the antibody against IDH2 R172. In 1 case, tumor tissue from 2 core needle biopsy samples collected on different days were also immunohistochemically positive for IDH2 R172. These results indicate that IDH2 R172 immunohistochemistry is suitable for the detection of TCCRP in both resection and biopsy samples. In addition, a literature review revealed that R172S and R172T account for 76% of IDH2 mutations in TCCRP, suggesting that 11C8B1, which reacts with R172S and R172T, was likely most sensitive for IDH2 -mutated TCCRP among many available antibodies for IDH2 R172. Furthermore, the combination of 2 or more antibodies against IDH2 R172 could be more effective for detecting TCCRP mutation. However, it is important to note that IDH2 R172 immunohistochemistry is not absolute, because IDH2 wild type is found in a small proportion (10%) of cases, and a few cases of IDH2 -mutated TCCRP may harbor rare subtypes of R172 that are not covered by available antibodies.

Dedifferentiation and progression of an intracranial solitary fibrous tumor: autopsy case of a Japanese woman with a history of radiation therapy of the head during infancy.

Solitary fibrous tumor (SFT) is usually an indolent neoplasm with a low rate of local recurrence and metastasis. Although dedifferentiation of low-grade sarcoma is well documented, the concept of dedifferentiated SFT was not recognized until recently. A case of intracranial SFT with seven recurrences within 5 years, showing progression and dedifferentiation during the course of disease, is reported here. A 51-year-old woman with a history of irradiation during infancy presented with a SFT in the right posterior fossa. Because of the close proximity to the brain stem, the tumor could not be removed completely. The tumor recurred 12, 16, and 28 months after the initial operation. With the repeated recurrences, cellularity, mitotic count, and Ki-67 (MIB-1) index increased gradually. The histology suddenly changed at the fourth recurrence, which occurred 16 months after postoperative radiation therapy for the third recurrence. The tumor revealed a fibrosarcoma-like appearance with necrosis and markedly increased mitotic activity. The tumor further recurred 50, 52, and 55 months after the initial operation with the same fibrosarcoma-like histology. The patient died of uncontrolled tumor 58 months after the initial operation. In this case radiation may have played some role in the tumorigenesis, progression, and dedifferentiation of the SFT.