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Pediatric renal tumors are a rare entity and majority of these tumors are accounted for by Wilms tumor. The second most common renal tumor is clear cell sarcoma of the kidney (CSSK). Most of the CSSK have either BCOR-internal tandem duplication (ITD) or YWHAE-NUTM2B/E fusion. The sarcomas with BCOR-CCNB3 fusion are well documented in soft tissue and bone tumors, but are extremely rare in the pediatric renal setting. We are reporting an extremely rare case of pediatric clear cell sarcoma of the kidney (CSSK) with BCOR-CCNB3 fusion, which was a diagnostic challenge on morphological grounds. A final diagnosis could only be reached after multiple reviews and NGS based RNA fusion testing. We have also performed a brief review of literature which revealed eight (8) other cases of this rare entity.

Introduction Marked variations in survival rates have brought into question whether standard clinicopathologic classification should be applied to patients presenting with multiple primary lung cancers (MPLCs). This study investigated the genetic profiles of MPLCs in a cohort of patients using next-generation sequencing and correlated results to clinicopathologic data and patient outcome. Methods Patients treated surgically with curative intent for two putative primaries of similar histopathology from January 2000 to December 2019 at St Vincent’s Hospital Melbourne. DNA and RNA was extracted from formalin-fixed, paraffin-embedded tumor tissue and sequenced on an Ion Torrent Personal Genome Machine system. Patient outcome was determined by overall survival and disease-free survival. Results A total of 40 cases fulfilled the inclusion criteria. Mutational profiling was concordant with clinicopathologic diagnosis in most cases; however, seven cases (17.5%) revealed shared mutations suggesting metastatic disease and this was associated with a substantial reduction in overall survival (p Conclusions Our results suggest that gene sequencing technologies are potentially a more accurate diagnostic and prognostic tool compared with traditional histopathologic evaluation in patients presenting with suspected MPLCs, which could better guide management and predict outcomes.

Since its discovery in 2007, we have seen the lives of patients diagnosed with advanced anaplastic lymphoma kinase (ALK)-rearranged non-small cell lung cancers (NSCLC) transform with the advent of molecular therapies with first-, second-, and third-generation ALK inhibitors now available in the clinic. Despite great gains in patient survival now measured in years and preserved quality of life with targeted therapies, drug resistance is unfortunately inevitably encountered in this rare and unique molecular subset of lung cancer, and patients will eventually succumb to the disease. As these patients are often young, fit, and never smokers, the clinical and scientific communities have aligned to expedite drug development and access. Drug resistance profiling and further strategies are being explored through clinical trials, including the evaluation of specific drug sequencing and combinations to overcome such resistance and promote patient longevity. The cases of this report focus on precision medicine and aim to portray the pertinent aspects to consider when treating ALK-rearranged NSCLC in 2020, an ever-shifting space. By way of case examples, this report offers valuable information to the treating clinician, including the evolution of systemic treatments and the management of oligo-progression and multisite drug resistance. With the maturation of real-world data, we are fortunate to be experiencing quality and length of life for patients with this disease surpassing prior expectations in advanced lung cancer. Key Points This report focuses on the importance of genetic analysis of serial biopsies to capture the dynamic therapeutic vulnerabilities of a patient's tumor, providing a perspective on the complexity of ALK tyrosine kinase inhibitor (ALKi) treatment sequencing. These case examples contribute to the literature on ALK-rearranged and oncogene addicted non-small cell lung cancer (NSCLC), providing a framework for care in the clinic. In oligo-progressive disease, local ablative therapy and continuation of ALKi postprogression should be considered with potential for sustained disease control. ALK G1202R kinase domain mutations (KDM), highly prevalent at resistance to second-generation ALKi resistances, may emerge in non-EML4-ALK variant 3 cases and is sensitive to third-generation lorlatinib. When in compound with one or more ALK KDMs, resistance to lorlatinib is expected. In the case of rampantly progressive disease, rebiopsy and redefining biology in a timely manner may be informative.

Pancreatic acinar cell carcinoma is relatively rare (1 to 2% of pancreatic malignancies) but may be under-recognized. In contrast to pancreatic ductal adenocarcinoma, most acinar cell carcinomas lack mutations in KRAS, DPC, CDKN2A or TP53, but appear to have a high incidence of gene rearrangements, with up to 20% reported to be driven by BRAF fusions. With the development of a new class of RET-specific tyrosine kinase inhibitors, which appear to have particularly strong activity against RET gene rearranged tumours, there is now considerable interest in identifying RET gene rearrangements across a wide range of cancers. RET rearrangements have been reported to occur at a very low incidence (

Structural rearrangements of the genome can drive lung tumorigenesis through the generation of fusion genes with oncogenic properties. Advanced genomic approaches have identified the presence of a genetic fusion between fibroblast growth factor receptor 3 (FGFR3) and transforming acidic coiled-coil 3 (TACC3) in non-small cell lung cancer (NSCLC), providing a novel target for FGFR inhibition. To interrogate the functional consequences of the FGFR3-TACC3 fusion in the transformation of lung epithelial cells, we generated a novel transgenic mouse model that expresses FGFR3-TACC3 concomitant with loss of the p53 tumor suppressor gene. Intra-nasal delivery of an Ad5-CMV-Cre virus promoted seromucinous glandular transformation of olfactory cells lining the nasal cavities of FGFR3-TACC3 (LSL-F3T3) mice, which was further accelerated upon loss of p53 (LSL-F3T3/p53). Surprisingly, lung tumors failed to develop in intra-nasally infected LSL-F3T3 and LSL-F3T3/p53 mice. In line with these observations, we demonstrated that intra-nasal delivery of Ad5-CMV-Cre induces widespread Cre-mediated recombination in the olfactory epithelium. Intra-tracheal delivery of Ad5-CMV-Cre into the lungs of LSL-F3T3 and LSL-F3T3/p53 mice however, resulted in the development of lung adenocarcinomas. Taken together, these findings provide in vivo evidence for an oncogenic function of FGFR3-TACC3 in respiratory epithelium.

We investigated correlations between diagnosis according to the 2015 World Health Organization (WHO) classification of unresected lung tumours, molecular analysis and TTF1 expression in small biopsy and cytology specimens from 344 non-small cell lung carcinoma (NSCLC) patients. One case failed testing for EGFR, KRAS and ALK abnormalities and six had insufficient tumour for ALK testing. Overall mutation rate in 343 cases was 48% for the genes tested, with 19% EGFR, 33% KRAS and 4% BRAF mutations, and 5% ALK rearrangements detected. More EGFR-mutant (78%) and ALK-rearranged (75%) tumours had morphologic adenocarcinoma than KRAS-mutant (56%) tumours. Despite no significant difference in the overall rate of any molecular abnormality between morphologic adenocarcinoma (52%) and NSCLC, favour adenocarcinoma (47%) (p = 0.18), KRAS mutations were detected more frequently in the latter group. No significant difference in the overall rate of any molecular abnormality between TTF1 positive (49%) and TTF1 negative tumours (44%) (p = 0.92) was detected, but more EGFR-mutant (97%) and ALK-rearranged tumours (92%) were TTF1 positive than KRAS-mutant tumours (68%). Rates of EGFR, KRAS and BRAF mutations and ALK rearrangements in this Australian NSCLC patient population are consistent with the published international literature. Our findings suggest that 2015 WHO classification of unresected tumours may assist in identifying molecular subsets of advanced NSCLC.

The advent of massively parallel sequencing has caused a paradigm shift in the ways cancer is treated, as personalised therapy becomes a reality. More and more laboratories are looking to introduce next generation sequencing (NGS) as a tool for mutational analysis, as this technology has many advantages compared to conventional platforms like Sanger sequencing. In Australia all massively parallel sequencing platforms are still considered in-house in vitro diagnostic tools by the National Association of Testing Authorities (NATA) and a comprehensive analytical validation of all assays, and not just mere verification, is a strict requirement before accreditation can be granted for clinical testing on these platforms. Analytical validation of assays on NGS platforms can prove to be extremely challenging for pathology laboratories. Although there are many affordable and easily accessible NGS instruments available, there are no standardised guidelines as yet for clinical validation of NGS assays. We present an accreditation development procedure that was both comprehensive and applicable in a setting of hospital laboratory for NGS services. This approach may also be applied to other NGS applications in service laboratories.

The KRAS oncoprotein, a critical driver in 33% of lung adenocarcinoma (LUAD), has remained an elusive clinical target due to its perceived undruggable nature. The identification of dependencies borne through common co-occurring mutations are sought to more effectively target KRAS-mutant lung cancer. Approximately 20% of KRAS-mutant LUAD carry loss-of-function mutations in KEAP1, a negative regulator of the antioxidant response transcription factor NFE2L2/NRF2. We demonstrate that Keap1-deficient KrasG12D lung tumors arise from a bronchiolar cell-of-origin, lacking pro-tumorigenic macrophages observed in tumors originating from alveolar cells. Keap1 loss activates the pentose phosphate pathway, inhibition of which, using 6-AN, abrogated tumor growth. These studies highlight alternative therapeutic approaches to specifically target this unique subset of KRAS-mutant LUAD cancers., Lung adenocarcinomas frequently harbour KRAS mutations, of which a subset are characterized by co-mutation of KEAP1. Here the authors show, in mice, that KrasG12D mutant tumours are metabolically distinct, with a bronchiolar cell-of-origin.

Pancreatic acinar cell carcinoma is relatively rare (1 to 2% of pancreatic malignancies) but may be under-recognized. In contrast to pancreatic ductal adenocarcinoma, most acinar cell carcinomas lack mutations in KRAS, DPC, CDKN2A or TP53, but appear to have a high incidence of gene rearrangements, with up to 20% reported to be driven by BRAF fusions. With the development of a new class of RET-specific tyrosine kinase inhibitors, which appear to have particularly strong activity against RET gene rearranged tumours, there is now considerable interest in identifying RET gene rearrangements across a wide range of cancers. RET rearrangements have been reported to occur at a very low incidence (1%) in all pancreatic carcinomas. We postulated that given its unique molecular profile, RET gene rearrangements may be common in acinar cell carcinomas. We performed fluorescent in-situ hybridization (FISH) studies on a cohort of 40 acinar cell spectrum tumours comprising 36 pure acinar cell carcinomas, three pancreatoblastomas and one mixed acinar-pancreatic neuroendocrine tumour. RET gene rearrangements were identified in 3 (7.5%) cases and BRAF gene rearrangements in 5 (12.5%). All gene rearranged tumours were pure acinar cell carcinomas. Our findings indicate that amongst all pancreatic carcinomas, acinar carcinomas are highly enriched for potentially actionable gene rearrangements in RET or BRAF. FISH testing is inexpensive and readily available in the routine clinical setting and may have a role in the assessment of all acinar cell carcinomas-at this stage to recruit patients for clinical trials of new targeted therapies, but perhaps in the near future as part of routine care.

OBJECTIVE: The efficacy of deep brain stimulation can be limited by factors including poor selectivity of stimulation, targeting error, and complications related to implant reliability and stability. We aimed to improve surgical outcomes by evaluating electrode leads with smaller diameter electrode and microelectrodes incorporated which can be used for assisting targeting. APPROACH: Electrode arrays were constructed with two different diameters of 0.65 mm and the standard 1.3 mm. Micro-electrodes were incorporated into the slim electrode arrays for recording spiking neural activity. Arrays were bilaterally implanted into the medial geniculate body (MGB) in nine anaesthetised cats for 24-40 h using stereotactic techniques. Recordings of auditory evoked field potentials and multi-unit activity were obtained at 1 mm intervals along the electrode insertion track. Insertion trauma was evaluated histologically. MAIN RESULTS: Evoked auditory field potentials were recorded from ring and micro-electrodes in the vicinity of the medial geniculate body. Spiking activity was recorded from 81% of the microelectrodes approaching the MGB. Histological examination showed localized surgical trauma along the implant. The extent of haemorrhage surrounding the track was measured and found to be significantly reduced with the slim electrodes (541 ± 455 µm vs. 827 ± 647 µm; P < 0.001). Scoring of the trauma, focusing on tissue disruption, haemorrhage, oedema of glial parenchyma and pyknosis, revealed a significantly lower trauma score for the slim electrodes (P < 0.0001). SIGNIFICANCE: The slim electrodes reduced the extent of acute trauma, while still providing adequate electrode impedance for both stimulating and recording, and providing the option to target stimulate smaller volumes of tissue. The incorporation of microelectrodes into the electrode array may allow for a simplified, single-step surgical approach where confirmatory micro-targeting is done with the same lead used for permanent implantation.

Background: We report a 61-year-old who presented with a right-sided abducens nerve palsy secondary to a middle cranial fossa adenoid cystic carcinoma (ACC) extending into the cavernous sinus. Purpose: This case represents a unique presentation of intracranial ACC with a large middle cranial fossa mass and only a small extracranial component. Methods: Review of the literature was undertaken to identify cases of intracranial ACC and their range of presentations. Results: Our results show that this is the first reported case of an ACC presenting mostly as an intracranial mass with an isolated cranial nerve lesion. Conclusion: Our case highlights the importance of a broad differential diagnosis, particularly in circumstances where there are atypical features of lesions on radiographic imaging.

The global landscape of molecular testing is rapidly changing, with the recent publication of the International Association for the Study of Lung Cancer (IASLC)/College of American Pathologists (CAP) guidelines and the ALK Atlas. The IASLC/CAP guidelines recommend that tumors from patients with non-small cell lung cancer (NSCLC) be tested for ALK rearrangements in addition to epidermal growth factor receptor (EGFR) mutations. The spur for this recommendation is the availability of novel therapies that target these rearrangements. This article is based on coverage of a Pfizer-sponsored National Working Group Meeting on ALK Diagnostics in Lung Cancer, held around the 15th World Lung Cancer Conference, in Sydney on October 31, 2013. It is based on the presentations given by the authors at the meeting and the discussion that ensued. The content for this article was discussed and agreed on by the authors.

// Gavin M. Wright 1 , Hongdo Do 2 , Jonathan Weiss 2 , Naveed Z. Alam 1 , Vivek Rathi 3 , Marzena Walkiewicz 4 , Thomas John 4 , Prudence A. Russell 3 , Alexander Dobrovic 2 1 University of Melbourne Department of Surgery, St Vincent’s Hospital Melbourne, Victoria, Australia. 2 Translational Genomics and Epigenomics Laboratory Ludwig Institute for Cancer Research Olivia Newton-John Cancer and Wellness Centre Heidelberg, Victoria, Australia. 3 Department of Anatomical Pathology St Vincent’s Hospital Melbourne, Victoria, Australia. 4 Ludwig Institute for Cancer Research, Olivia Newton-John Cancer and Wellness Centre Heidelberg, Victoria, Australia. 5 Department of Pathology, University of Melbourne, Melbourne, Victoria, Australia. Correspondence: Gavin M. Wright, email: // Keywords : BRAF, EGFR, KRAS, high resolution melting, polymerase chain reaction, tumor heterogeneity. Received : Febuary 25, 2014 Accepted : March 20, 2014 Published : March 22, 2014 Abstract Precision medicine depends on the accurate identification of actionable mutations in a tumor sample. It is unknown how heterogeneous the distribution of such mutations can be in a tumor. Morphological (i.e. histopathological) heterogeneity is well described in lung adenocarcinoma and has been specifically recognized in the most recent official clinico-pathological classification. The most predominant subtype present is now used to classify each lung adenocarcinoma. No molecular profile exists to explain the intratumoral differences in lung adenocarcinoma morphology, despite the consistently observed association between specific predominant subtypes and poorer survival. Given a recent proposal stratifying lung adenocarcinoma into subtypes of differing metastatic potential, we questioned the assumption that major mutations are present uniformly throughout tumors; especially those showing discrete different subtypes. We selected formalin-fixed paraffin embedded lung adenocarcinoma specimens that showed discrete areas of different subtypes, extracted subtype DNA samples from those areas and screened for mutations in hotspot regions of the EGFR , KRAS and BRAF genes using high resolution melting. Sanger sequencing was used to confirm all identified mutations. Chromogenic in situ hybridization (CISH) was used to identify mutant allele specific imbalances in tumors with EGFR mutations. Interestingly, we found that KRAS and BRAF mutations could be confined to morphological domains of higher grade. On the other hand, EGFR mutations were found through all histological subtypes in each tumor consistent with the driver status of this mutation. Intratumoral heterogeneity has major implications for tumorigenesis, chemoresistance and the role of histopathology in molecular screening for precision medicine. This study not only confirms that intratumoral mutational heterogeneity does occur, but also that it is associated with morphologically distinct regions in some tumors. From a practical perspective, small biopsies may not adequately represent a tumor’s full mutational profile, particularly for later arising but prognostically important mutations such as those in the KRAS and BRAF genes.

Purpose: To compare and contrast the clinical, radiologic, pathologic, and genetic features of patients with ocular adnexal IgG4-related disease (IgG4-RD) and patients with adult ocular adnexal xanthogranulomatous disease (XG). Methods: This retrospective review study identified patients with histological evidence of either disease from records of the pathology department of our hospital from 1996 to 2014. Clinical, imaging, and a variety of histopathologic features were collected for 23 patients with IgG4-RD and 13 patients with XG. Next generation sequencing with a 50-gene cancer screening panel was performed on biopsy tissues from 10 patients in each group. Results: Statistical differences between the 2 groups include eyelid (67%; p = 0.0002) and anterior orbital (75%; p = 0.0352) predilection for XG except for Erdheim-Chester disease subgroup which was more posterior and diffuse. Eyelid involvement was rare (4%) for IgG4-RD. Involvement of orbital nerves was seen in 30% of IgG4-RD and 0% in XG (p = 0.0695). Five patients with IgG4-RD developed malignancy (4 lymphoma, 1 leiomyosarcoma), but none of XG patients. Discriminating pathological features were the presence of any IgG4+ plasma cells (p = 0.0121) and the ratio of IgG4+/IgG+ plasma cells (p =0.0294) for IgG4-RD. Five of 12 (42%) patients with XG had sufficient numbers of IgG4+ plasma cells/high power field to fulfill published diagnostic criteria for IgG4-RD, and 5 (42%) had a ratio of IgG4+/IgG+ plasma cells over 40%, but the numbers overall were less than seen in the IgG4-RD patients. The only genetic difference between the 2 groups was that BRAF V600E mutation was found in 1 of the 2 Erdheim-Chester disease patients, which form a subgroup of XG. Conclusions: IgG4-RD and XG share clinical, imaging, and histopathological features including IgG4+ plasma cells. Significant differences were the eyelid involvement in XG, orbital nerve involvement, and an elevated IgG4+/IgG+ ratio in IgG4-RD and the only genetic abnormality found was BRAF V600E mutation in the Erdheim-Chester disease subgroup of XG.

The lung presents a highly oxidative environment, which is tolerated through engagement of tightly controlled stress response pathways. A critical stress response mediator is the transcription factor nuclear factor erythroid-2-related factor 2 (NFE2L2/NRF2), which is negatively regulated by Kelch-like ECH-associated protein 1 (KEAP1). Alterations in the KEAP1/NRF2 pathway have been identified in 23% of lung adenocarcinomas, suggesting that deregulation of the pathway is a major cancer driver. We demonstrate that inactivation of Keap1 and Pten in the mouse lung promotes adenocarcinoma formation. Notably, metabolites identified in the plasma of Keap1f/f/Ptenf/f tumor-bearing mice indicate that tumorigenesis is associated with reprogramming of the pentose phosphate pathway. Furthermore, the immune milieu was dramatically changed by Keap1 and Pten deletion, and tumor regression was achieved utilizing immune checkpoint inhibition. Thus, our study highlights the ability to exploit both metabolic and immune characteristics in the detection and treatment of lung tumors harboring KEAP1/NRF2 pathway alterations.

The global landscape of molecular testing is rapidly changing, with the recent publication of the International Association for the Study of Lung Cancer (IASLC)/College of American Pathologists (CAP) guidelines and the ALK Atlas. The IASLC/CAP guidelines recommend that tumors from patients with non-small cell lung cancer (NSCLC) be tested for ALK rearrangements in addition to epidermal growth factor receptor (EGFR) mutations. The spur for this recommendation is the availability of novel therapies that target these rearrangements. This article is based on coverage of a Pfizer-sponsored National Working Group Meeting on ALK Diagnostics in Lung Cancer, held around the 15th World Lung Cancer Conference, in Sydney on October 31, 2013. It is based on the presentations given by the authors at the meeting and the discussion that ensued. The content for this article was discussed and agreed on by the authors.

Active Vibration Control (AVC) using smart structure is used to reduce the vibration of a system by automatic modification of the system structural response. AVC is widely used, because of its wide and broad frequency response range, low additional mass, high adaptability and good efficiency. A lot of research has been done on Finite Element (FE) models for AVC based on Euler Bernoulli Beam Theory (EBT). In the present work Timoshenko Beam Theory (TBT) is used to model a smart cantilever beam with surface mounted sensors / actuators. A Periodic Output Feedback (POF) Controller has been designed and applied to control the first three modes of vibration of a flexible smart cantilever beam. The difficulties encountered in the usage of surface mounted piezoelectric patches in practical situations can be overcome by the use of embedded shear sensors / actuators. A mathematical model of a smart cantilever beam with embedded shear sensors and actuators is developed. A POF Controller has been designed and applied to control of vibration of a flexible smart cantilever beam and effect of actuator location on the performance of the controller is investigated. The mathematical modeling and control of a Multiple Input multiple Output (MIMO) systems with two sensors and two actuators have also been considered.

Well-differentiated papillary mesothelioma (WDPM) is an uncommon tumor usually arising in the peritoneum and mostly an incidental finding during abdominal and pelvic surgery. Its natural history and association with other neoplasms is not clearly understood. We present a rare case of WDPM in association with high-grade endometrial carcinoma. To our knowledge, there are only two previously reported cases in the English literature of WDPM in association with endometrial carcinoma.A 62-year-old woman underwent pelvic surgery for a high-grade endometrial adenocarcinoma. At laparotomy an extensive peritoneal nodular fibrotic reaction was present, raising the clinical possibility of metastatic disease; however, intraoperative frozen section reported this as a mesothelial reaction. Cytologic examination of peritoneal washings revealed cohesive clusters of reactive-appearing mesothelial cells, some with papillary morphology, and no evidence of adenocarcinoma. The peritoneal biopsies showed no metastatic carcinoma. The endometrial tumor was an endometrioid adenocarcinoma.The cytologic diagnosis of WDPM may be difficult because it is an uncommon entity and there are overlapping features with other neoplastic and nonneoplastic lesions of the female genital tract and peritoneum. Compounding this, WDPM may occur in association with other neoplasms. We highlight the potential for surgical and pathologic misinterpretation of this entity.

This paper presents an efficient algorithm for disparity map computation with an adaptive window by establishing two frame stereo correspondence. Adaptive window based approach has a clear advantage of producing dense depth maps from stereo images. In recent years there has not been much research on adaptive window based approach due its high complexity and large computation time. Adaptive window based method selects an appropriate rectangular window by evaluating the local variation of the intensity and the disparity. Ideally the window need not be rectangular but to reduce algorithmic complexity and hence computation time, rectangular window is taken. There is a need for correction of errors introduced due to the rectangular window which is not dealt by the existing algorithm. To reduce this error, a method has been proposed which not only improves the disparity maps but also has a lesser computational complexity. To demonstrate the effectiveness of the algorithm the experimental results from synthetic and real image pairs (provided by middlebury research group) including ones with ground-truth values for quantitative comparison with the other methods are presented. The proposed algorithm outperforms most of the existing algorithms evaluated in the taxonomy of dense two frame stereo algorithms. The implementation has been done in C++. The algorithm has been tested with the standard stereo pairs which are used as benchmark for comparison of algorithms in the taxonomy implementation.

Purpose Lymphomatoid granulomatosis (LYG) is a rare multisystem disease involving the lungs, skin, and nervous system. 1,2 Here we present a case of LYG diagnosed on omental biopsy taken at laparotomy suspecting a primary ovarian tumour. Methods Pieces of omentum were fixed in 10% neutral-buffered formalin, embedded in paraffin, and cut sections stained in haematoxylin and eosin. Mycobacterial, fungal and gram stains, TB PCR and immunohistochemical studies including EBER for Epstein-Barr virus, PCR for gene rearrangement studies and flow cytometry were performed. Results The omental biopsies showed diffuse infiltrate of small lymphocytes, some in an angiocentric pattern, poorly formed granulomas and patchy fat necrosis. The infiltrate consisted predominantly of T-cells with no aberrant staining and a minority (less than 1%) of mildly enlarged EBER positive B-lymphocytes, not readily apparent on H&E sections. No T or B-cell monoclonality was identified. TB PCR and antibody studies for ANA and ANCA were negative. Discussion LYG is an Epstein-Barr virus related lymphoproliferative disorder of B-cell lineage. 3 Grading of LYG depends on the proportion of EBV-positive B-cells relative to reactive lymphocytic background. 1,4 Grade 1 lesion can be difficult to diagnose as only a few atypical large cells are present, highlighted on immunohistochemistry. 1,5

Purpose We report a rare case of large atypical ossifying fibromyxoid tumour (OFMT) in an unusual site, the anterior mediastinum, in a 51-year-old female. Methods The tumour was fixed in 10% neutral-buffered formalin, embedded in paraffin, and cut sections stained in haematoxylin-eosin. Immunohistochemistry for variety of tumour markers were performed. Results Histopathology revealed a tumour surrounded by thick fibrous pseudo-capsule, paucicellular fibrous septae extending inwards and tumour lobules containing variably cellular arrangement of plump epithelioid cells with ovoid nuclei and inconspicuous eosinophilic cytoplasm, surrounded by fibromyxoid stroma. Tiny areas of metaplastic bone were present in fibrous septae. Scattered areas of necrosis and mitosis up to 3 per 10 high power fields (hpf) were noticed. Tumour cells were positive for vimentin, S-100 and NSE, showed scattered nuclear positivity for AE1/3 and were negative for EMA, actin, desmin, GFAP, Melan-A, CD34, CD21 and CD57. Discussion OFMT is a rare neoplasm of uncertain lineage, commonly arising in extremities, trunk, head and neck, oral cavity and rarely in retroperitoneum and mediastinum. 1–6 Few have atypical or malignant features, designated atypical or malignant OFMT and are characterised by a combination of hypercellularity, high nuclear grade, increased mitosis of more than 2 per 50 hpf and necrosis. 1–5