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A 12-year-old, 3 kg spayed female mixed-breed dog was evaluated to assess a 1-year history of intermittent right forelimb lameness that did not have adequate response to nonsteroidal anti-inflammatory drugs. The radiographic study performed under sedation showed multifocal radiolucent areas affecting both the right humerus and scapula with focal soft tissue swelling; a CT scan confirmed the existence of an aggressive and invasive soft tissue mass affecting the scapulohumeral joint. Fine needle aspiration results suggested a low-grade synovial sarcoma and therefore a scapulectomy was performed. The biopsy showed spindle to stellated cells immersed in a basophilic and mucinous (myxoid) matrix with mild to moderate anisocytosis, moderate anisokaryosis, some binucleated cells and sporadic multinucleated cells. These findings are consistent with low-grade synovial myxosarcoma, a not well described synovial neoplasm that can mimic other commonly seen joint tumors or even septic arthritis on radiographs. The purpose of this case report is to describe the first reported synovial myxosarcoma affecting the scapulohumeral joint of a small dog.

Background Primary pulmonary myxoid sarcoma (PPMS) is a rare, low-grade malignant tumor, constituting approximately 0.2% of all lung tumors. Despite its rarity, PPMS possesses distinctive histological features and molecular alterations, notably the presence of EWSR1-CREB1 gene fusion. However, its precise tissue origin remains elusive, posing challenges in clinical diagnosis. Case demonstration A 20-year-old male patient underwent a routine physical examination 6 months prior, revealing a pulmonary mass. Following surgical excision, microscopic evaluation unveiled predominantly short spindle-shaped tumor cells organized in a fascicular, beam-like, or reticular pattern. The stromal matrix exhibited abundant mucin, accompanied by lymphocytic and plasma cell infiltration, with Russell bodies evident in focal areas. Immunophenotypic profiling revealed positive expression of vimentin and epithelial membrane antigen in tumor cells, whereas smooth muscle actin and S-100, among others, were negative. Ki-67 proliferation index was approximately 5%. Subsequent second-generation sequencing identified the characteristic EWSR1-CREB1 gene fusion. The definitive pathological diagnosis established PPMS. The patient underwent no adjuvant chemotherapy or radiotherapy and remained recurrence-free during a 30-month follow-up period. Conclusions We report a rare case of PPMS located within the left lung lobe interlobar fissure, featuring Russell body formation within the tumor stroma, a novel finding in PPMS. Furthermore, the histomorphological characteristics of this case highlight the diagnostic challenge it poses, as it may mimic inflammatory myofibroblastic tumor, extraskeletal myxoid chondrosarcoma, or hemangiopericytoma-like fibrous histiocytoma. Therefore, accurate diagnosis necessitates an integrated approach involving morphological, immunohistochemical, and molecular analyses.

Background Myxofibrosarcomas (MFS) are a historically heterogeneous group of tumors that exhibit a propensity for local recurrence. The objectives of this study were to analyze the prognostic factors and outcomes of patients with MFS treated at a single institution. Methods We retrospectively reviewed the records of 69 consecutive patients with pathologically confirmed MFS of the extremities or superficial trunk who underwent surgery from August 1995 to November 2010. Clinicopathologic features, treatments, and patient outcomes were reviewed. Results Sixty-nine patients were identified, of whom 38 were men (55 %). The median age was 62 years. Sixty-four patients (93 %) presented with primary tumors, and 5 patients (7 %) presented with locally recurrent tumors. Median tumor size was 6.0 cm, and 44 patients (64 %) had grade 3 tumors (FNCLCC [Fédération Nationale des Centres de Lutte Contre le Cancer] classification). Margins were microscopically positive in 14 patients (20 %) and negative in 55 patients (80 %), including close margins (<1 mm) in 14 patients (20 %). Fifty-three patients (77 %) received radiotherapy. At a median follow-up of 41 months, there were 11 local (16 %) and 11 distant (16 %) recurrences. The local and distant 5-year recurrence-free survival rates were 72 % and 82 %, and the 5-year overall survival was 61 %. Increased age (scaled by 0.1; hazard ratio [HR] 1.80, P  = 0.002) and tumor size (HR 1.12, P  = 0.004) were negatively correlated with overall survival. Positive/close (<1 mm) margin status (HR 4.34, P  = 0.030) predicted worsened local recurrence-free survival. Conclusions MFS exhibit a propensity for local recurrence, which is predicted by resection with positive or close margins. Aggressive surgery combined with radiotherapy may contribute to more effective local control.

Myxoinflammatory fibroblastic sarcoma is a rare soft tissue tumor with most occurring in the distal extremities of adult patients. It has a high rate of local recurrence and a low rate of metastasis. Because it may appear benign on clinical examination, and because the microscopic features are generally underrecognized, it is often inadequately treated and misdiagnosed. In this review, based upon experience and that of the literature, the intent is to highlight salient clinicopathologic features, detail the broad microscopic spectrum including high-grade aggressive variants, review the molecular features, and discuss its relation to hemosiderotic fibrolipomatous tumor.

Myxoinflammatory fibroblastic sarcoma (MIFS) is a malignant mesenchymal neoplasm most frequently arising in the distal extremities of adults, which usually behaves in a low-grade manner but is capable of metastasizing to local and distant sites, rarely leading to death. It is a rare tumor whose unusual morphology can lead to erroneous histologic diagnosis, either as a nonneoplastic (infectious or inflammatory) process or as a variety of neoplastic diseases. While its exact origin is uncertain, ultrastructural studies have shown at least some of the constituent cells to be modified fibroblasts. Distinct and reproducible genetic abnormalities identified in MIFS are translocation t(1;10)(p22:q24), with rearrangements of the TGFBR3 and MGEA5 genes associated with increased levels of FGF8, and formation of marker/ring chromosome 3, with amplification of the VGLL3 locus. Because these genetic abnormalities are shared by both MIFS and hemosiderotic fibrohistiocytic lipomatous tumor, it is thought that these 2 morphologically distinct neoplasms may comprise a spectrum of disease defined by these genetics. We review the literature on MIFS and discuss morphology (including that of MIFS/hemosiderotic fibrohistiocytic lipomatous tumor hybrid lesions), immunohistochemistry, the differential diagnosis, and recent molecular genetic developments.

Background The majority of primary, intraocular tumors in cats originate from the uvea and include feline diffuse iris melanoma, lymphoma, and iridociliary epithelial adenoma or adenocarcinoma. In this case report, we describe for the first time the clinical, histological, and immunohistochemical findings of a rare myxoid intraocular neoplasm arising from the ciliary body in a cat. Case presentation A 14-year-old, female, spayed domestic shorthaired cat was presented for evaluation of discolouration of the right eye. Upon examination, a clear to light whitish-tan, bubble-shaped intraocular mass adherent to the inferior ciliary body and extending into the anterior chamber was noted. Within five weeks, the tumor was significantly larger and the eye had developed secondary glaucoma so was enucleated. Light microscopic examination of the globe revealed a multinodular, hypocellular neoplasm arising from the ciliary body composed of interwoven spindle cells embedded in abundant amounts of a lightly basophilic myxoid matrix. Neoplastic cells exhibited strong immunoreactivity for cytokeratin while also showing moderate to strong immunoreactivity to vimentin. A diagnosis was therefore made of an unusual intraocular myxoid epithelioid sarcoma arising from the ciliary body. Conclusions Although apparently exceedingly rare, epithelioid myxosarcoma should be included as a differential diagnosis for intraocular tumors in cats and they represent a clinical, histologic, and immunohistochemical diagnostic challenge. Early surgical intervention should be considered to prevent local invasion and ascension to the brain.

Background Soft tissue sarcomas (STS) are generally considered non-immunogenic, although specific subtypes respond to immunotherapy. Antitumour response within the tumour microenvironment relies on a balance between inhibitory and activating signals for tumour-infiltrating lymphocytes (TILs). This study analysed TILs and immune checkpoint molecules in STS, and assessed their prognostic impact regarding local recurrence (LR), distant metastasis (DM), and overall survival (OS). Methods One-hundred and ninety-two surgically treated STS patients (median age: 63.5 years; 103 males [53.6%]) were retrospectively included. Tissue microarrays were constructed, immunohistochemistry for PD-1, PD-L1, FOXP3, CD3, CD4, and CD8 performed, and staining assessed with multispectral imaging. TIL phenotype abundance and immune checkpoint markers were correlated with clinical and outcome parameters (LR, DM, and OS). Results Significant differences between histology and all immune checkpoint markers except for FOXP3+ and CD3−PD-L1+ cell subpopulations were found. Higher levels of PD-L1, PD-1, and any TIL phenotype were found in myxofibrosarcoma as compared to leiomyosarcoma (all p  < 0.05). The presence of regulatory T cells (Tregs) was associated with increased LR risk ( p  = 0.006), irrespective of margins. Other TILs or immune checkpoint markers had no significant impact on outcome parameters. Conclusions TIL and immune checkpoint marker levels are most abundant in myxofibrosarcoma. High Treg levels are independently associated with increased LR risk, irrespective of margins.

Background Myxofibrosarcoma is genetically complex and remains obscure in molecular determinants of clinical aggressiveness. Our prior study revealed recurrent gains of 7q in myxofibrosarcomas where MET and CDK6 genes displayed increased DNA copies. Previously, we demonstrated the implication of MET overexpression, prompting us to further elucidate the roles of CDK6 in myxofibrosarcomas. Materials On tissue microarrays, CDK6 immunoexpression was assessable in 77 primary tumors, 55 of which were successfully quantified for CDK6 and MET genes by real-time PCR using genomic DNA extracted from laser-microdissected tumor cells. Gene status and protein expression of CDK6 were correlated with each other, clinicopathological variables, metastasis-free survival (MFS), and disease-specific survival (DSS). Results Protein overexpression and gene amplification of CDK6, which were detected in 21 of 77 (27.2 %) and 13 of 55 cases (23.6 %), respectively, were highly related to each other ( p  < .001) and associated with higher grades (overexpression, p  = .004; amplification, p  = .014). There was a strong correlation between CDK6 and MET gene copies ( p  < .001, r  = 0.0714). Importantly, CDK6 protein overexpression (MFS, p  = .0002; DSS, p  = .0015) and gene amplification (MFS, p  = .0001; DSS, p  = .0083) were both univariately associated with worse outcomes. Together with nonextremity location and AJCC stage III disease, CDK6 overexpression independently portended inferior MFS ( p  = .0015, risk ratio [RR] = 7.411). This aberration, along with nonextremity location, was also an independent adverse prognosticator of DSS ( p  = .0069, RR = 6.006). Conclusions In approximately a quarter of primary myxofibrosarcomas, CDK6 overexpression is mostly driven by gene amplification on 7q, associated with adverse prognosticators, and independently predictive of worse outcomes, highlighting its possible causative role in tumor aggressiveness.

Myxofibrosarcoma is a malignant fibroblastic soft tissue neoplasm containing a variable amount of myxoid stroma that commonly presents as a slow-growing mass in elderly patients. The neoplasm may be superficial or deep to the muscle fascia and characteristically has an infiltrative growth pattern with a dominant or multinodular mass. We describe an unusual case of high-grade myxofibrosarcoma of the wrist and forearm that infiltrated the muscles, tendons, and wrist joint, causing bone erosions. The tumor was mistakenly diagnosed as synovitis and a chronic, erosive, inflammatory process. The diffuse nature, absence of a dominant mass, and radiographic appearance complicated the diagnosis. Although neoplasms of the synovial spaces are rare, this case demonstrates that tumors with a highly infiltrative growth pattern can mimic inflammatory synovitis and that neoplasms should be considered in the differential diagnosis when clinical and laboratory features are discordant with the imaging appearance.

Background Attenuated endogenous protein levels of cyclin-dependent kinase 2 associated protein 1 (p12 CDK2AP1 ) and its active homodimer p25 CDK2AP1 were found in myxofibrosarcoma-derived cell lines. Clinical and biological significances of this putative tumor suppressor in myxofibrosarcoma were studied. Methods Plasmids carrying the CDK2AP1 gene and small hairpin RNA interference (shRNAi) targeting CDK2AP1 were transfected into NMFH-1 and/or OH931 cells to evaluate the effects on the CDK2, active caspase 3 (CASP3), cleaved-CASP8 and -CASP9 levels, cell cycle regulation, and/or apoptotic responses. Immunostaining of p12 CDK2AP1 was interpretable in 102 primary myxofibrosarcomas and correlated with clinicopathological variables, CDK2, Ki-67 and active CASP3 protein levels, and disease-specific survival. Results Exogenous expression of p12 CDK2AP1 in NMFH-1 and OH931 cells significantly induced G 0 /G 1 cell cycle arrest and down-regulated CDK2 protein level. In NMFH-1 cells, these aspects were reversed by shRNAi targeting CDK2AP1 gene. Increased active CASP3 and cleaved-CASP9, but not -CASP8, were detected after CDK2AP1 overexpression, suggesting the cellular apoptosis were induced through the mitochondrial pathway. Immunostains of p12 CDK2AP1 were aberrantly decreased in 56.9 % of cases; positively and negatively correlated with protein levels of CDK2 ( p  = 0.023), Ki-67 ( p  = 0.001) and active CASP3 ( p  < 0.001), respectively. Following by high histological grades, p12 CDK2AP1 down-regulation was predictive of worse disease-specific survival in univariate ( p  = 0.003) and multivariate ( p  = 0.004) analyses. Conclusions Through down-regulation of CDK2, high p12 CDK2AP1 level induced cell cycle arrest and the mitochondrial-dependent apoptotic pathway. Low p12 CDK2AP1 level represents a poor prognostic factor in patients with myxofibrosarcoma.