Synovial sarcoma with extensive osteoid and bone formation

Synovial Sarcoma of the Gastrointestinal Tract

We report the clinicopathologic and immunohistochemical features of 18 cases of confirmed primary synovial sarcoma of the gastrointestinal tract. The neoplasms arose in 10 women and 8 men ranging in age from 23 to 81 years (mean: 50; median: 57.5 years). The tumors for which size was known ranged from 1.8 to 15.0 cm (mean: 5.2; median: 5.1 cm). Microscopically, 14 synovial sarcomas were of the monophasic type, 2 were biphasic, and 2 were poorly differentiated. Immunohistochemical analysis of 4 cases showed strong, diffuse staining for SS18::SSX (4/4 cases). Pancytokeratin and EMA immunohistochemistry were performed on 13 and 9 tumors, respectively, and each showed patchy-to-diffuse staining. By reverse-transcription PCR, 3 cases were positive for the SS18::SSX1, and 2 cases were positive for the SS18::SSX2 gene fusion. Six cases contained an SS18 gene rearrangement by fluorescence in situ hybridization, and next-generation sequencing identified an SS18::SSX2 gene fusion in one case. Clinical follow-up information was available for 9 patients (4 months to 4.6 years; mean, 2.8 y; median: 29 months), and one patient had a recent diagnosis. Three patients died of disease within 41 to 72 months (mean, 56 months) of their diagnosis. Five patients were alive without evidence of disease 4 to 52 months (mean, 17.6 months) after surgery; of whom 1 of the patients received additional chemotherapy treatment after surgery because of recurrence of the disease. A single patient was alive with intraabdominal recurrence 13 months after surgery. We conclude that synovial sarcoma of the gastrointestinal tract is an aggressive tumor, similar to its soft tissue counterpart, with adverse patient outcomes. It is important to distinguish it from morphologically similar gastrointestinal tract lesions that may have different treatment regimens and prognoses.

Biphasic synovial sarcoma with myoepithelial features: a distinctive variant with a predilection for the foot

Synovial sarcoma (SS) is a tumor known for its classic monophasic spindle cell or biphasic morphology. However, it exhibits a wide range of histologic variations, leading to diagnostic challenges. Here, we present four cases of molecularly confirmed, biphasic SS originating in the feet and displaying myoepithelial differentiation. The patients were two men and two women with an age range from 19 to 71 years (mean, 45 years). Each tumor showed foci with conventional spindle cell morphology. The epithelial components included areas with nests and cords of epithelioid cells set within a hyalinized and sclerotic stroma. The cytoplasm was clear to pale and eosinophilic. The nuclei were ovoid-round with fine chromatin and small to inconspicuous nucleoli. Mitotic figures were present (2-13 per 10 high-power fields; mean, 6.5). Immunohistochemical studies showed variable staining of the myoepithelial-like regions for low molecular weight keratins, EMA, p63, and S100 protein. Molecular studies confirmed the presence of SS18::SSX1/2 fusion in all four tumors. These cases highlight an unusual variant of synovial sarcoma with an apparent predilection for the distal lower extremity and suggest that differentiation of biphasic synovial sarcoma may be impacted by the anatomic site. Awareness of this variant is important to avoid misclassification and potential treatment and prognostic implications.

Synovial sarcoma with ossification and calcification with SS18 immunochemical expression and rearrangement by fluorescent in situ hybridization

Synovial sarcoma is a soft tissue tumor of uncertain origin. Generally, it is a monophasic spindle cell neoplasm that can have glandular-like structures. Ossification and presence of calcification is a rare phenomenon with only a few reported cases. We present the case of a young male with a synovial sarcoma of the right foot. Histology revealed prominent deposits of tumoral osteoid and coarse calcifications. The diagnosis was confirmed by the expression of SS18 by immunohistochemistry and the demonstration of the rearrangement of the SS18 gene by fluorescent in situ hybridization. We reviewed the literature for synovial sarcoma with prominent ossification or calcification, and to the best of our knowledge, this is the first case with expression of SS18 by immunohistochemistry. The main differential diagnoses are osteosarcoma (both primary of bone and extraosseous) and sclerosing epithelioid fibrosarcoma.

ZFP64::NCOA3 gene fusion defines a novel subset of spindle cell rhabdomyosarcoma

Spindle cell rhabdomyosarcoma represents a rare neoplasm characterized by monomorphic spindle cells with a fascicular architecture and variable skeletal muscle differentiation. Following incidental identification of a ZFP64::NCOA3 gene fusion in an unclassified spindle cell sarcoma resembling adult-type fibrosarcoma, we performed a retrospective archival review and identified four additional cases with a similar histology and identical gene fusion. All tumors arose in adult males (28-71 years). The neoplasms were found in the deep soft tissues, two were gluteal, and one each arose in the thigh, abdominal wall, and chest wall. Morphologically, the tumors were characterized by spindle cells with a distinctive herringbone pattern and variable collagenous to myxoid stroma. The nuclei were relatively monomorphic with variable mitotic activity. Three tumors had immunoreactivity for MyoD1, and four contained variable expression of desmin and smooth muscle actin. All cases tested for myogenin, CD34, S100, pankeratin, and epithelial membrane antigen were negative. Targeted RNA sequencing revealed a ZFP64::NCOA3 fusion product in all five tumors. Three patients developed distant metastases, and two ultimately succumbed to their disease within 2 years of initial diagnosis. This study suggests ZFP64::NCOA3 fusions define a novel subtype of rhabdomyosarcoma with a spindle cell morphology and aggressive clinical behavior. The potential for morphologic and immunohistochemical overlap with several other sarcoma types underscores the value of molecular testing as a diagnostic adjunct to ensure accurate classification and management of these neoplasms.

Synovial sarcoma of the spinal canal and paraspinal muscle and retroperitoneum: a case with extensive calcification

INTRODUCTION

Synovial sarcoma (SS) is a rare mesenchymal malignant tumor. SS of the spine or retroperitoneum is an extremely rare site. Approximately 30% cases show focal calcifications on radiographs and computed tomography (CT) images, while extensive calcification rarely occurs. We presented a case of SS involving the spinal canal and paraspinal muscle and retroperitoneum, which showed extensive calcification on CT.

CLINICAL PRESENTATION

The present report describes the case of a 13-year-old girl suffering from a tumor in the spinal canal and paraspinal muscle and retroperitoneum with extensive calcification on CT. The patient underwent lumbar and retroperitoneal giant tumor resection, lumbar decompression, and spinal tumor resection with a small tumor remnant remaining in the paravertebral region. Histological examination and genetic testing after surgery confirmed synovial sarcoma. After surgery, the patient refused local radiotherapy but agreed to receive chemotherapy. After 4 months of follow-up, her condition was basically stable, and the pain in her left lower limb disappeared. The residual tumor was not increased.

CONCLUSION

Extensive calcification of SS is rare. The possibility of synovial sarcoma should be considered in those who show extensive calcification in the spinal canal and paraspinal muscle and retroperitoneum on CT. For cases that cannot be completely resected, adjuvant chemotherapy can control the residual tumor in the short term. In addition, the long-term effects need to be observed.

Synovial Sarcoma of the Female Genital Tract: A Protean Mimic of Müllerian Neoplasia

Synovial sarcoma most commonly occurs in the extremities but has rarely been described in the female genital tract. In this series, we describe the clinical, morphologic, immunohistochemical, and molecular features of 7 cases of vulvovaginal synovial sarcoma (vulva, n=6; vagina, n=1). We emphasize their wide morphologic spectrum, which can overlap significantly with other more common tumors at these sites, as highlighted by 2 cases initially diagnosed as other entities (endometrioid carcinoma and malignant peripheral nerve sheath tumor). The average patient age was 41 (range: 23 to 62) years and tumor size ranged from 0.8 to 7 cm. Histologically, the tumors were biphasic (n=6) and monophasic (n=1). All cases were confirmed with fluorescence in situ hybridization or sequencing, and 5/5 cases were positive for the novel immunohistochemical markers SSX and SS18-SSX. In 3 cases with follow-up, 2 patients died of disease and 1 was alive with no evidence of disease. Previously described cases arising in the female genital tract are also reviewed. Vulvovaginal monophasic synovial sarcoma raises a broad differential diagnosis, including smooth muscle tumors, spindled carcinomas, and melanoma. Biphasic synovial sarcoma may mimic Müllerian carcinosarcoma, endometrioid carcinoma with spindled, corded, and hyalinized elements, and mesonephric-like adenocarcinoma. Awareness that synovial sarcoma can occur in the female genital tract with a wide variety of histologic appearances is critical for correctly diagnosing this rare entity. In particular, synovial sarcoma should be considered for any deeply situated "adenocarcinoma" in the vulva, with attention to subtle spindle cell differentiation.

Treatment and outcomes for synovial sarcoma patients in Western Australia: the role of neoadjuvant chemoradiotherapy

Background

This is a retrospective review of synovial sarcoma (SS) patients treated over the last 12 years in Western Australia (WA). SS is both chemo and radiotherapy sensitive. Results of trials in adjuvant chemotherapy are conflicting and there is limited support for neoadjuvant chemotherapy. The use of combined chemoradiotherapy is based on institutional preferences.

Aim

We reviewed the outcomes for SS patients treated in WA over a 12 year period focusing on patients who received neoadjuvant chemoradiotherapy (NACRT).

Methods

Patient details including demographics, histopathology, treatment details, were obtained from the WA sarcoma database (2006‐2018). Progression free survival (PFS) and overall survival (OS) were derived for whole cohort.

Results

Twenty seven patients were identified with SS with equal gender incidence. Median age of the cohort was 36 (14‐76) years. The most common primary site of disease was extremity (81.5%). 22/27 patients presented with only localized disease and 59.2% of these received neo‐adjuvant treatment. Of those who received neoadjuvant treatment, 56.2% had NACRT, while 25.0% and 18.7% of patients had chemotherapy and radiotherapy respectively. Mesna, doxorubicin, ifosfamide, dacarbazine (MAID) was the most commonly used chemotherapy regimen as neoadjuvant or adjuvant treatment while ifosfamide (93.7%) was the most commonly used chemotherapy drug in any setting. There was no reported case of disease progression in group of patients who received NACRT apart from one patient who had oligometastatic disease at diagnosis. Median OS of the whole cohort was 38 months while median PFS was 24 months. Bone marrow toxicity was the most commonly reported high grade toxicity in NACRT group (55.5%) but there were no treatment related deaths.

Conclusion

NACRT is not widely adopted and treatment is based on institutional preferences, however our data shows that NACRT is a feasible therapy option. NACRT should be evaluated prospectively in a randomized trial.

Underlying Ossification Phenotype in a Murine Model of Metastatic Synovial Sarcoma

Synovial sarcoma, an uncommon cancer, typically affects young adults. Survival rates range from 36% to 76%, decreasing significantly when metastases are present. Synovial sarcomas form in soft tissues, often near bones, with about 10% demonstrating ossification in the tumor. The literature is inconclusive on whether the presence of ossification portends a worse prognosis. To this end, we analyzed our genetic mouse models of synovial sarcoma to determine the extent of ossification in the tumors and its relationship with morbidity. We noted higher ossification within our metastatic mouse model of synovial sarcoma. Not only did we observe ossification within the tumors at a frequency of 7%, but an even higher frequency, 72%, of bone reactivity was detected by radiography. An enrichment of bone development genes was associated with primary tumors, even in the absence of an ossification phenotype. In spite of the ossification being intricately linked with the metastatic model, the presence of ossification was not associated with a faster or worse morbidity in the mice. Our conclusion is that both metastasis and ossification are dependent on time, but that they are independent of one another.

Genetic and molecular reappraisal of spindle cell adamantinoma of bone reveals a small subset of misclassified intraosseous synovial sarcoma

Adamantinoma represents a distinct group of bone tumors showing both mesenchymal and epithelial differentiation most commonly involving the tibial diaphysis. Most adamantinomas contain a fibro-osseous component and an epithelial component consisting of squamous or basaloid cells. Adamantinomas are considered malignant neoplasms requiring en bloc excision that frequently recur locally and can rarely metastasize. Rare adamantinomas show an epithelial component consisting predominantly of monomorphic spindle cells, which, combined with an epithelial immunophenotype, can mimic monophasic synovial sarcoma. Synovial sarcoma is very rare in bone. It is considered a high-grade sarcoma that typically necessitates chemotherapy. However, the relationship between spindle cell adamantinoma and intraosseous synovial sarcoma has not been investigated. The current study was prompted by identification of a presumed spindle cell adamantinoma of the tibia with diffuse keratin expression that harbored a SS18 gene region rearrangement. FISH of eight additional bone tumors initially classified as spindle cell adamantinoma based on clinicoradiopathologic findings revealed one additional case with SS18 rearrangement. Histologically, both intraosseous synovial sarcoma and spindle cell adamantinoma demonstrated uniform fusiform nuclei with scant cytoplasm, short fascicles and low mitotic activity. The adamantinomas, but not the synovial sarcomas, were more likely to show overt epithelial differentiation in the form of pseudoglands or squamous nests. Immunohistochemistry of all cases, irrespective of SS18 status, showed diffuse keratin positivity in the spindle cell component, and less consistent EMA positivity. Clinical follow-up was available in both intraosseous synovial sarcomas, one of which recurred and the other metastasized. Two of the six spindle cell adamantinomas with follow-up metastasized. The above findings highlight the morphologic and immunophenotypic overlap between spindle cell adamantinoma and intraosseous synovial sarcoma of the tibia. Investigation of SS18 status to exclude synovial sarcoma is suggested prior to rendering a diagnosis of spindle cell adamantinoma.

A rare case of retroperitoneal synovial sarcoma

Management of retroperitoneal soft tissue sarcomas is complex. Treatment is usually multimodal; involving surgery, chemotherapy and radiotherapy.

Paracrine osteoprotegerin and β-catenin stabilization support synovial sarcomagenesis in periosteal cells

Synovial sarcoma (SS) is an aggressive soft-tissue sarcoma that is often discovered during adolescence and young adulthood. Despite the name, synovial sarcoma does not typically arise from a synoviocyte but instead arises in close proximity to bones. Previous work demonstrated that mice expressing the characteristic SS18-SSX fusion oncogene in myogenic factor 5-expressing (Myf5-expressing) cells develop fully penetrant sarcomagenesis, suggesting skeletal muscle progenitor cell origin. However, Myf5 is not restricted to committed myoblasts in embryos but is also expressed in multipotent mesenchymal progenitors. Here, we demonstrated that human SS and mouse tumors arising from SS18-SSX expression in the embryonic, but not postnatal, Myf5 lineage share an anatomic location that is frequently adjacent to bone. Additionally, we showed that SS can originate from periosteal cells expressing SS18-SSX alone and from preosteoblasts expressing the fusion oncogene accompanied by the added stabilization of β-catenin, which is a common secondary change in SS. Expression and secretion of the osteoclastogenesis inhibitory factor osteoprotegerin enabled early growth of SS18-SSX2-transformed cells, indicating a paracrine link between the bone and synovial sarcomagenesis. These findings explain the skeletal contact frequently observed in human SS and may provide alternate means of enabling SS18-SSX-driven oncogenesis in cells as differentiated as preosteoblasts.

Polypoid Carcinoma of the Oropharynx with Stromal Ossifying Myofibroblastic Proliferation: A Case Report and Literature Review

A 76-year-old man reported a worsening difficulty in swallowing, leading to the inability to eat. Physical examination and CT scan revealed a polypoid mass on the posterior oropharynx and obstructing the oropharyngeal space. Histologically, the surface was ulcerated. In the underlying necrotic rim, there was active granulation tissue, and a proliferation of voluminous, globoid elements with hyperchromatic and irregular nucleus, sometimes arranged in a alveolar aggregate. The core of the lesion contained spindle-like myoid elements in interwoven bundles, with trabeculae of osteoid matrix maturing into calcified bone. Immunohistochemistry documented positivity for cytokeratins, epithelial membrane antigen, and P63 in the globoid elements beneath the necrotic rim; strong and diffuse expression of vimentin, smooth muscle actin, and CD99 and BCL2 in the spindle elements; and complete negativity for cytokeratin 5/6, high molecular weight cytokeratin (clone 34βE12), S100, muscle-specific actin, desmin, CD117, and anaplastic lymphoma kinase. The lesion was morphologically and immunophenotypically classified as a polypoid oropharyngeal carcinoma with ossifying myofibroblastic stromal proliferation.

Periosteal Osteosarcoma of the Digits

A periosteal osteosarcoma arose in the first phalanx of the fourth finger of a 32-year-old woman's right hand. She had no predisposing factors for this cancer. The tumor was initially locally resected, but as recurrences developed, the finger and later the hand were amputated. Despite therapy with doxorubicin and cisplatin, distant metastases occurred and ultimately caused the patient's death. Primary conventional osteosarcomas of the short tubular bones of the hands and feet are rare, but surface lesions are rarer. This case constitutes the first reported periosteal osteosarcoma to arise in a phalanx.

Intracapsular Chondroma of the Knee: An Unusual Neoplasm

Intracapsular chondroma is a rare lesion that has been reported under different names on 23 occasions. We describe a 52-year-old woman with intracapsular chondroma that involved the left knee. Radiologically, the mass was multilobulated, calcified, and sharply circumscribed and was lying between the patella and the anterolateral surface of the tibia. The peculiar histologic pattern of the tumor was composed of hyaline cartilage nodules with enchondral ossification or calcification, in apparent transition with septa of connective and adipose tissue. The most common differential diagnoses for this tumor are primary synovial chondromatosis and chondrosarcoma. We emphasize a possible metaplastic origin of the chondromatous component due to some mechanical posttraumatic disturbance of the infrapatellar fat pad. To our knowledge, the present case is the second intracapsular chondroma to be described in the European literature.

A Rare Pediatric Example of Subcutaneous Extraskeletal Osteosarcoma: A Case Report and Review of the Morphologic Differential Diagnosis

Primary extraskeletal osteosarcoma is an exceedingly rare malignant neoplasm that accounts for approximately 1% of soft tissue sarcomas and most often occurs in the deep soft tissues of adults. Extraskeletal osteosarcoma is characterized by the production of osteoid, bone, and/or chondroid matrix. The diagnosis of extraskeletal osteosarcoma requires careful radiologic and clinical correlation to ensure that the patient does not have an underlying bone primary. This is a case report of primary subcutaneous extraskeletal osteosarcoma arising in the thigh of a 15-year-old girl with a complex karyotype, and the morphologic differential diagnosis is reviewed.

[Synovial tumors and tumor-like lesions]

Synovial tumors comprise a variety of lesions, including those with benign and aggressive neoplastic changes as well as inflammatory causes. In this article we focus on neoplastic tumors. Synovial tumors with other etiologies, such as sarcoidosis, granuloma, synovitis, or gouty arthritis, are not dealt with here. Through a precise differentiation between these disease entities can an optimization of treatment be achieved.

Chondro-Osseous Lesions of Soft Tissue

Soft tissue lesions can contain bone or cartilage matrix as an incidental, often metaplastic, phenomenon or as a diagnostic feature. The latter category includes a diverse group ranging from self-limited proliferations to benign neoplasms to aggressive malignancies. Correlating imaging findings with pathology is mandatory to confirm that a tumor producing bone or cartilage, in fact, originates from soft tissue rather than from the skeleton. The distinction can have dramatic diagnostic and therapeutic implications. This content focuses on the gross, histologic, radiographic, and clinical features of bone or cartilage-producing soft tissue lesions. Recent discoveries regarding tumor-specific genetics are discussed.

Soft tissue sarcomas of the kidney

Soft tissue sarcomas are rare mesenchymal tumors. Amongst others, primitive neuroectodermal tumors (PNET) of the kidney and synovial sarcoma of the kidney belong to the group of soft tissue sarcomas. Synovial sarcomas can occur almost anywhere in the body, most frequently, however, in the lower (62%) or upper extremities (21%). Metastases occur in 50-70% of cases, and thus the prognosis is poor. PNETs are rare, highly aggressive neoplastic lesions which mainly occur in the torso or axial skeleton in young adults. The prognosis is poor with a 5-year disease-free survival rate of 45-55%. The primary therapeutic approach is surgical resection. Most randomized studies assessing adjuvant chemotherapy for all types of localized soft tissue sarcomas did not show statistically significantly better overall survival times after chemotherapy, although they did show longer progression-free survival. We report on two cases of primary renal synovial sarcoma and one case of PNET of the kidney.

Synovial sarcoma: defining features and diagnostic evolution

Synovial sarcoma (SS) is a malignant mesenchymal neoplasm with variable epithelial differentiation, with a propensity to occur in young adults and which can arise at almost any site. It is generally viewed and treated as a high-grade sarcoma. As one of the first sarcomas to be defined by the presence of a specific chromosomal translocation leading to the production of the SS18-SSX fusion oncogene, it is perhaps the archetypal "translocation-associated sarcoma," and its translocation remains unique to this tumor type. Synovial sarcoma has a variety of morphologic patterns, but its chief forms are the classic biphasic pattern, of glandular or solid epithelial structures with monomorphic spindle cells and the monophasic pattern, of fascicles of spindle cells with only immunohistochemical or ultrastructural evidence of epithelial differentiation. However, there is significant morphologic heterogeneity and overlap with a variety of other neoplasms, which can cause diagnostic challenge, particularly as the immunoprofile is varied, SS18-SSX is not detected in 100% of SSs, and they may occur at unusual sites. Correct diagnosis is clinically important, due to the relative chemosensitivity of SS in relation to other sarcomas, for prognostication and because of the potential for treatment with specific targeted therapies in the near future. We review SS, with emphasis on the diagnostic spectrum, recent immunohistochemical and genetic findings, and the differential diagnosis.

Intraspinal dural-based primary osteoblastoma with aneurysmal bone cyst-like change

Osteoblastoma is a benign bone-forming neoplasm that occurs commonly in the posterior elements of the spine and the sacrum. However, so far there has been no report of intradural osteoblastoma described in the literature. We present a unique case of intraspinal dural-based osteoblastoma with aneurysmal bone cyst-like change without evidence of vertebral involvement. An 11-year-old Chinese girl presented with a 3-month history of gradually progressive back pain and a weakness of both lower limbs. Thoracic MRI revealed a well-demarcated subdural mass at the T5 level with heterogeneous enhancement. Histologically, the tumor was found to be attached to the dura and composed of numerous osteoid spicules and trabecular bone with diffusely scattered osteoclast-type, multinucleated giant cells. Ectactic blood vessels and blood-filled cystic spaces were also observed. A diagnosis of primary intraspinal dural-based osteoblastoma with aneurysmal bone cyst-like change was made. To our best knowledge, this is possibly the first case of primary osteoblastoma arising from meninges. Meningeal osteocartilaginous tumors are rare, with obscure histogenesis. The differential diagnosis of osteoblastoma in unusual locations is difficult and the confirmation of diagnosis should be cautiously made. Awareness of dural-based osteoblastoma and its histological features is important to avoid a diagnostic pitfall caused by histological similarities to other intra-craniospinal lesions with osteoid differentiation or bone formation.

Inhibin-α and synaptophysin immunoreactivity in synovial sarcoma with granular cell features

We recognized immunoreactivity for the α subset of inhibin and synaptophysin in synovial sarcomas with granular cell features. Histologic findings of 90 cases of synovial sarcoma were reviewed. Two (2.2%) of the 90 cases had granular cell features, showing sheet or nested proliferation of characteristic epithelioid cells with abundant eosinophilic and granular cytoplasm, in addition to the typical spindle cell component. The 2 cases were both female (aged 86 and 76 years). The tumors were located in the foot and the retroperitoneum and measured 3.5 and 14 cm in maximum diameter. Reverse transcriptase polymerase chain reaction analysis revealed SS18-SSX1 transcripts in both cases. SS18 gene rearrangement was detected in granular cells as well as spindle cells by chromogenic in situ hybridization. Immunohistochemistry found the granular cells to be positive for inhibin-α in both cases and for synaptophysin in 1 case, whereas spindle cells were not. Thirty-six cases (20 monophasic fibrous, 11 biphasic, and 5 poorly differentiated synovial sarcomas) were additionally examined for comparison; they showed no immunoreactivity for inhibin-α or synaptophysin. This is the first report of immunoreactivity for inhibin-α and synaptophysin in synovial sarcoma. These immunohistochemical findings might be characteristic of synovial sarcomas with granular cell features.

Expression of smooth muscle calponin in synovial sarcoma

Purpose. Histogenesis of synovial sarcoma remains controversial and reliable molecular markers for diagnosis are necessary. Expression of basic calponin, a smooth muscle differentiation-specific actin-binding protein, was studied in synovial sarcoma.Subjects and Methods. The basic calponin gene and the gene product were analyzed by reverse transcription PCR analysis (RT-PCR) and immunohistochemistry in 14 synovial sarcomas and a human synovial sarcoma cell line (HS-SY-II).Results and Discussion. Immunoreactivity for basic calponin was detected in the cytoplasm of 6 synovial sarcomas (43% positive). In the basic calponin-positive tumors and the HS-SY-II cells, expression for smooth muscle-specific genes, including basic calponin and SM22alpha , was detected by RT-PCR, suggesting a lineage relationship between synovial sarcoma cells and smooth muscle-like mesenchymal cells.Conclusions. A subset of synovial sarcomas expressing the basic calponin gene and the gene product were identified. The basic calponin may have potential utility as a novel molecular marker identifying certain synovial sarcomas.

Diagnosis and treatment of primary synovial cell sarcoma that occurred in the left mandible body: a case report and literature review

OBJECTIVE

The authors describe a case of synovial sarcoma in the left mandible body.

STUDY DESIGN

The primary tumor was investigated morphologically and immunohistochemically. The patient was treated with madibulectomy and lymph node dissection, which was followed by an immediate reconstruction of the left mandible with a revascularized osteomyocutaneous fibula free flap.

RESULTS

The primary tumor was described as gingival sarcoma. The initial preoperative biopsy showed positive staining for cytokeratin, vimentin, smooth muscle actin, and desmin by immunohistochemistry. The definitive diagnosis of monophasic synovial sarcoma was established following postoperative excision biopsy. Antigens of S-100 and CD99 displayed positive staining but epithelial membrane antigen, Bcl-2, and CD34 were negative. Also, no metastasis or other bone swelling was observed by radionuclide survey suggesting the left mandible was the primary lesion of occurrence.

CONCLUSIONS

Synovial sarcoma is an uncommon soft tissue malignant neoplasm. This is the sixth case of primary synovial sarcoma occurring in the jaw.

Synovial sarcoma is a stem cell malignancy

Synovial sarcoma (SS) is a malignant soft tissue tumor characterized by its unique t(X;18)(p11;q11) chromosomal translocation leading to the formation of the SS18-SSX fusion gene. The resulting fusion protein product is considered to play as an aberrant transcription factor and transform target cells by perturbing their gene expression program. However, the cellular origin of SS is highly debated. We herein established two novel human SS cell lines, named Yamato-SS and Aska-SS, and investigated their biological properties. We found the self-renewal ability of these cells to generate sarcospheres, to form tumors in serial xenotransplantation and reconstitute the tumor phenotypes without fractionation by any surface markers. Both SS cells as well as clinical tissue specimens from 15 patients expressed the marker genes-associated stem cell identity, Oct3/4, Nanog, and Sox2. We also found that both SS cells displayed limited differentiation potentials for mesenchymal lineages into osteocytes and chondrocytes albeit with the expression of early mesenchymal and hematopoietic lineage genes. Upon SS18-SSX silencing with sequence-specific siRNAs, these SS cells exhibited morphological transition from spherical growth in suspension to adherent growth in monolayer, additional expression of later mesenchymal and hematopoietic lineage genes, and broader differentiation potentials into osteocytes, chondrocytes, adipocytes, and macrophages in appropriate differentiation cocktails. Collectively, these data suggest that a human multipotent mesenchymal stem cell can serve as a cell of origin for SS and SS is a stem cell malignancy resulting from dysregulation of self-renewal and differentiation capacities driven by SS18-SSX fusion protein.

Synovial sarcomas usually metastasize after >5 years: a multicenter retrospective analysis with minimum follow-up of 10 years for survivors

BACKGROUND

Synovial sarcoma (SS) is a malignant soft tissue sarcoma with a poor prognosis because of late local recurrence and distant metastases. To our knowledge, no studies have minimum follow-up of 10 years that evaluate long-term outcomes for survivors.

PATIENTS AND METHODS

Data on 62 patients who had been treated for SS from 1968 to 1999 were studied retrospectively in a multicenter study. Mean follow-up of living patients was 17.2 years and of dead patients 7.7 years.

RESULTS

Mean age at diagnosis was 35.4 years (range 6-82 years). Overall survival was 38.7%. The 5-year survival was 74.2%; 10-year survival was 61.2%; and 15-year survival was 46.5%. Fifteen patients (24%) died of disease after 10 years of follow-up. Local recurrence occurred after a mean of 3.6 years (range 0.5-14.9 years) and metastases at a mean of 5.7 years (range 0.5-16.3 years). Only four patients were treated technically correctly with a planned biopsy followed by a wide resection or amputation. Factors associated with significantly worse prognosis included larger tumor size, metastases at the time of diagnosis, high-grade histology, trunk-related disease, and lack of wide resection as primary surgical treatment.

CONCLUSIONS

In SS, metastases develop late with high mortality. Patients with SS should be followed for >10 years.

Sox9 expression is not limited to chondroid neoplasms: variable occurrence in other soft tissue and bone tumors with frequent expression by synovial sarcomas

The transcription factor Sox9 is known to play a crucial role in normal chondrogenesis, and antibodies against Sox9 have been proposed as a diagnostic tool for neoplasms with chondroid differentiation. However, the pattern of Sox9 immunohistochemical expression by other bone and soft tissue neoplasms, as well as its diagnostic specificity, remain unexplored. The authors have performed immunohistochemistry with antibodies against Sox9 in 106 chondroid and nonchondroid bone and soft tissue neoplasms. Moderate to intense Sox9 nuclear staining was observed in 14/20 chondrosarcomas (70%), and in 24/81 (29.6%) cases from a multitumor tissue microarray, which included 16/18 synovial sarcomas, 4/15 osteosarcomas, 2/5 peripheral primitive neuroectodermal tumor (PNET)/Ewing sarcomas, 1/1 mesenchymal chondrosarcoma, and 1/1 chondroblastoma. The results suggest that Sox9 usefulness in the diagnosis of chondroid tumors may be limited because of low sensitivity and specificity. The finding of Sox9 expression by 88.9% of synovial sarcomas represents a novel and striking observation, which deserves further investigation.

Recurrence of synovial chondromatosis of the Hoffa's body

Synovial chondromatosis of Hoffa's body is uncommon. Recurrences usually result from incomplete removal of the loose bodies or diseased synovium at the initial surgery. We report a patient with synovial chondromatosis localized into the Hoffa's body who presented with anterior knee pain and mechanical symptoms. At the first arthroscopy, all pathological tissue was removed. At 1-year follow-up, clinical and radiographic examinations were normal. Symptoms recurred at 3 years, when a bony mass in the Hoffa's body was evident on MRI. The mass was removed through a mini-arthrotomy. Histology excluded malignancy. At 10-year follow-up, the patient remained free of symptoms. Synovial chondromatosis can occur with unusual patterns of recurrence. The growth of a large size mass confined to fat pad without intra-articular involvement does not allow to exclude the diagnosis of recurrent synovial chondromatosis.

From the archives of the AFIP: Imaging of synovial sarcoma with radiologic-pathologic correlation

Synovial sarcoma is the fourth most common type of soft-tissue sarcoma, accounting for 2.5%-10.5% of all primary soft-tissue malignancies worldwide. Synovial sarcoma most often affects the extremities (80%-95% of cases), particularly the knee in the popliteal fossa, of adolescents and young adults (15-40 years of age). Despite its name, the lesion does not commonly arise in an intraarticular location but usually occurs near joints. Histologic subtypes include monophasic, biphasic, and poorly differentiated; the cytogenetic aberration of the t(X;18) translocation is highly specific for synovial sarcoma. Although radiographic features of these tumors are not pathognomonic, findings of a soft-tissue mass, particularly if calcified (30%), near but not in a joint of a young patient, are very suggestive of the diagnosis. Cross-sectional imaging features are vital for staging tumor extent and planning surgical resection; they also frequently reveal suggestive appearances of multilobulation and marked heterogeneity (creating the "triple sign") with hemorrhage, fluid levels, and septa (creating the "bowl of grapes" sign). Two features associated with synovial sarcoma that may lead to an initial mistaken diagnosis of a benign indolent process are slow growth (average time to diagnosis, 2-4 years) and small size (< 5 cm at initial presentation); in addition, these lesions may demonstrate well-defined margins and homogeneous appearance on cross-sectional images. Synovial sarcoma is an intermediate- to high-grade lesion, and, despite initial aggressive wide surgical resection, local recurrence and metastatic disease are common and prognosis is guarded. Understanding and recognizing the spectrum of appearances of synovial sarcoma, which reflect the underlying pathologic characteristics, improve radiologic assessment and are important for optimal patient management.

[Morphological variability of synovial sarcoma in childhood]

We report on an unusual locally recurrent plantar soft tissue sarcoma in a 7-years-old boy. Due to an unusual morphology a clear diagnosis was initially not possible. The histologically different recurrent tumor was classified as synovial sarcoma by means of immunohistochemistry, ultrastructural and molecular analysis. This case demonstrates the variable morphological appearance of synovial sarcoma and the value of modern diagnostic procedures in such circumstances.

Spindle cell ossifying amyloidotic tumor of the fallopian tube

We report a unique tumor of the fallopian tube that was an incidental finding in a 60-year-old woman. The tumor was characterized by nests of spindle cells embedded in a partially ossified, hyalinized stroma, that also contained amyloid and basement membrane-like material. The histologic appearance of the tumor cells suggested an epithelial nature, but no immunohistochemical or ultrastructural evidence of such was found. The circumscription of the tumor and its lack of mitotic activity and cytologic atypia suggest a benign nature, but the histogenesis and appropriate classification of the tumor remain unclear.

Mineralization in musculoskeletal leiomyosarcoma: radiologic-pathologic correlation

OBJECTIVE

Mineralization in leiomyosarcoma, a malignant tumor of smooth muscle, has not been widely recognized. In this article, we report our experience with four cases of primary leiomyosarcoma of soft tissue or bone in which mineralization was visible on either radiography or CT. In none of the cases was the diagnosis of leiomyosarcoma considered before biopsy. In one case of a soft-tissue leiomyosarcoma, the presence of mineralization was a factor that led to the misinterpretation of the needle biopsy specimen as soft-tissue osteosarcoma.

CONCLUSION

Histologically, mineralization in leiomyosarcoma appears to be caused by either nonneoplastic ossification or dystrophic mineralization in the tumor. This feature can cause leiomyosarcomas to be confused with other neoplasms.

Synovial sarcoma with massive ossification--a case report

Synovial sarcoma with extensive osteoid production is rare. We report a case of synovial sarcoma of monophasic type with massive ossification. The diagnosis was confirmed by reverse-transcripitase polymerase chain reaction (RT-PCR). The patient was an-81-year-old woman with recurrent synovial sarcoma in her right knee. The tumor was primarily excised in 1989. It recurred and was removed again in 1996. However, in 1999 a painful mass appeared in the same site. Preoperative plain radiography and computed tomography revealed a 5 x 5 cm soft tissue mass with extensive ossification in the medial side of the right knee joint. The tumor was widely excised in 2000. Soft X-ray examination revealed a trabecular pattern of ossification in the excised tumor. Microscopically the tumor was composed of hypercellular spindle cells with fascicular arrangement with prominent ossification but no epithelial component. The tumor cells were positive for vimentin and focally positive for cytokeratin. The tumor expressed a sequence of SYT-SSX1 fusion gene transcript demonstrated by RT-PCR. Twelve years long survival of the present case without metastasis in spite of repeated recurrence suggests a better prognosis of synovial sarcomas with ossification.

Extraskeletal osteosarcoma histologically mimicking parosteal osteosarcoma

An extraskeletal osteosarcoma histologically mimicking parosteal osteosarcoma arising in a 63-year-old female is described. The intramuscular lesion in the left lower thigh was a 7 x 4 cm, well-defined mass with marked central calcification and ossification. The tumor was composed predominately of a centrally located osteocartilaginous component and a peripheral, non-osseous fibrous component. The former was characterized by a complex interanastomosing pattern of woven-bone trabeculae with small osteocytes and a minor cartilaginous element. The intratrabecular stroma consisted of benign-appearing fibroblasts. The peripheral fibrous part was characterized by fascicular and interlacing proliferations of spindle cells with mild atypia, rare mitosis and low to moderate cellularity. There were a few scattered foci of proliferating pleomorphic cells, constituting 5% of the tumor, indicating high-grade transformation. There was no evidence of zoning phenomena, cortical erosion, periosteal reaction or intramedullary involvement. The patient is well without recurrence or metastasis at 12 months follow up. This soft tissue neoplasm, mimicking parosteal osteosarcoma, should be distinguished from other bone-forming tumors or tumor-like lesions with which they may be confused. Pathologists and physicians should know the existence of this type of extraskeletal osteosarcoma and treat it as a high-grade extraskeletal osteosarcoma.

Calcifying/ossifying synovial sarcoma shows t(X;18) with SSX2 involvement and mitochondrial calcifications

AIMS

Synovial sarcoma with extensive calcification and ossification is a rare variant, the ultrastructural, cytogenetic and molecular analysis of which has not been reported previously.

METHODS AND RESULTS

A large mass in the shoulder of a 20-year-old male patient led to a deformity of the chest wall, thus supporting the hypothesis that this is a slowly growing variant of synovial sarcoma. Nevertheless, the patient developed metastatic lung disease 7 months after resection. On histology, the monophasic spindle cell proliferation was in several areas obscured by the massive calcification and ossification. Immunohistochemistry showed keratin, epithelial membrane antigen, vimentin and CD99 expression. The cytogenetic analysis revealed a single t(X;18)(p11.2; q11.2), typical for synovial sarcoma. Additional fluorescence in-situ hybridization revealed SSX2 involvement. At the ultrastructural level, prominent needle-shaped intramitochondrial crystals were present, both in the cytoplasm and in the extracellular matrix.

CONCLUSION

The presence of the t(X;18) with SSX2 involvement definitively characterizes this tumour as a variant of synovial sarcoma. In addition, the needle-like mitochondrial calcifications give a possible clue to the pathogenesis of the extensive metaplastic ossification and calcification.

Synovial sarcoma of the extremities: a clinicopathologic study of 34 cases, including semi-quantitative analysis of spindled, epithelial, and poorly differentiated areas

Many clinicopathologic studies of synovial sarcoma have grouped together tumors from different sites. The goal of this study was to identify clinical and pathologic features that correlate with a poor outcome in patients with extremity synovial sarcoma. Thirty-four cases of synovial sarcoma of the extremities were studied. Inclusion criteria included a consistent histology, the immunohistochemical expression of at least one epithelial marker (AE1/3, CAM 5.2, or epithelial membrane antigen), and adequate clinical follow-up. Features evaluated included the presence and extent of spindled, epithelial, and poorly differentiated areas, the presence and extent of calcification and necrosis, nuclear grade, the presence or absence of cells with a rhabdoid morphology, and the number of mitotic figures (MFs) per 10 high power fields (HPFs). Patients were considered to have an adverse outcome if they developed metastatic disease or died from tumor. The cohort included 15 males and 19 females with a median age 36 years (range, 11-82 years). There were 22 lower extremity tumors and 12 located on the upper extremities. Tumor size ranged from 1.2 to 16 cm (median, 6 cm). Follow-up ranged from 9 to 108 months (median, 38 months). Eleven (32%) patients had an adverse outcome, all with metastatic disease. Features associated with an adverse outcome included increasing age (p = 0.04), tumor size of 5 cm or greater (p = 0.03), tumor location on the lower extremities (p = 0.04), the presence of poorly differentiated areas (p = 0.04), grade 3 nuclei (p = 0.005), cells with a rhabdoid morphology (p = 0.003), and more than 10 MFs/10 HPFs (p = 0.005). Patients whose tumors were composed of at least 20% poorly differentiated areas were significantly more likely to have an adverse outcome (p < 0.001). In conclusion, a variety of clinical and pathologic features are associated with an adverse outcome in patients with synovial sarcoma of the extremities. These features include increasing age, tumor size of 5 cm or more, lower extremity tumor location, the presence of poorly differentiated areas, particularly when at least 20% of the tumor, grade 3 nuclei, rhabdoid cells, and more than 10 MFs/10 HPFs.

Lymphoma presenting as a soft tissue mass. A soft tissue sarcoma simulator

Lymphoma presenting as a soft tissue mass is rare and thus may be confused with the more common soft tissue sarcoma. No previous analysis of the clinical and radiologic features of lymphomas presenting as soft tissue masses is available because most of the cases reviewed are from the pathology literature. Four patients with diagnoses of extranodal lymphomas of the soft tissues were reviewed retrospectively with respect to their clinical features, primary tumor characteristics, stage, radiographic characteristics, treatment, and followup. Mean age was 72.5 years (range, 52-85 years). The soft tissue mass occurred in the thigh (three cases) and shoulder (one case). The median size of the soft tissue mass was 6.7 cm (range, 2-15 cm) in the largest dimension, as measured on magnetic resonance imaging. These patients each had evidence of lymphadenopathy at the time of diagnosis. Lactate dehydrogenase was increased significantly in two cases and increased slightly in two other cases. One case was Stage II(E) at presentation, one was Stage III(E), and two were Stage IV. All were B cell immunophenotype. All patients died between 2 and 24 months after diagnosis, despite the use of Cytoxan, vincristine, adriamycin, and prednisone chemotherapy in each case. Clinical and radiographic features that favor extranodal soft tissue lymphoma over sarcoma include pain and tenderness, lymphadenopathy (particularly when confluent radiologically), ipsilateral extremity swelling, and elevated lactate dehydrogenase.

Synovial sarcoma

Synovial sarcoma is a rare soft tissue tumor of children and adults that is unrelated to synovium and can occur in almost any part of the body. The familiar biphasic synovial sarcoma has discernible glandular or solid epithelial structures, and monophasic forms have characteristic ovoid or spindle cells with only immunohistochemical or ultrastructural evidence of epithelial differentiation. There are several morphologic patterns, including myxoid and hemangiopericytic, and behaviorally distinct calcifying, ossifying, and poorly differentiated subtypes can be recognized. Most synovial sarcomas are immunoreactive for cytokeratin, epithelial membrane antigen, and bc12 protein, and negative for CD34, and many express S100 protein and CD99 (MIC2). Nearly all synovial sarcomas have a specific t(x;18) (p11.2;q11.2) chromosomal abnormality, resulting in fusion of either of two variants of the SSX gene with the SYT gene; the genetic features may relate to morphology and outcome. The differential diagnosis can include a wide range of spindled, polygonal, or round cell sarcomas. Clinically, there have been marked recent improvements in local control of disease and lesser ones in management of metastases. The pathology, differential diagnosis, and behavior of this unique tumor are reviewed.

Synovial sarcoma of the neck

Primary synovial sarcoma of the head and neck region is a rare tumor. This report describes seven cases of primary synovial sarcomas, of which two were in the parapharyngeal region, two in the supraclavicular region, and one each in the hypopharynx, sternocleidomastoid and submandibular regions. Clinical presentations, radiological findings, histopathology and management are reviewed. All patients received multimodal therapy using aggressive surgery, radiotherapy and chemotherapy. Five of the patients are alive and disease free after 24-108 months of follow-up. Achievement of locoregional control appears to be the hallmark of successful therapy.

Parachordoma. A case report of a very rare soft tissue tumor

An extremely rare and peculiar soft tissue tumor is described. Few examples of this tumor are classified under the term parachordoma, while probably many more are designated as chordoid sarcomas. The tumor presents histological features similar to those of chordoma, as well as to extraskeletal myxoid chondrosarcomas (chordoid sarcomas), and should also be differentiated from chondroid syringoma or mixed tumor of the skin. The tumor reported herein appeared as a deep cited soft tissue mass, presenting the histology of chordoma in an extra-axial localization. On the other hand, the positive immunoreactions of the tumor cells with cytokeratin and epithelial membrane antigen (EMA) ruled out the diagnosis of chondrosarcoma. It seems, therefore, that this is a special type of soft tissue tumor with bimodal differentiation (epithelial and mesenchymal) with good prognosis.