Monophasic synovial sarcoma, epithelioid sarcoma and chordoid sarcoma: ultrastructural evidence for a common histogenesis, despite light microscopic diversity

Molecular cytogenetic characterization of proximal-type epithelioid sarcoma

Proximal-type epithelioid sarcoma is a recently described soft-tissue tumor that is distinguished from conventional-type epithelioid sarcoma by a far more aggressive clinical course, frequent location in the proximal anatomic regions, and variable rhabdoid morphology. Because of their rarity and peculiar morphology, proximal-type epithelioid sarcomas frequently pose serious diagnostic dilemmas, being easily misdiagnosed as a variety of other malignant neoplasms. To date, the information available on the genetic alterations associated with this tumor entity has been confined to single conventional cytogenetic reports. In this article, we present the results of a conventional and molecular cytogenetic analysis of six proximal-type epithelioid sarcomas. Spectral karyotyping analysis of these cases deciphered the characteristics of several marker chromosomes and complex translocations, leading to the recognition of recurrent rearrangements. The most frequently involved chromosome arm was 22q, and the identification of two cases with a similar translocation, t(10;22), suggests a role for one or more genes on chromosome 22 in the pathogenesis of this tumor and provides an opportunity for finely mapping the translocation-associated breakpoints. Chromosome arm 8q gain was also a frequent event and correlated with gain of MYC gene copy number, as demonstrated by fluorescence in situ hybridization. A review of both cases reported in the literature and those presented in this study reinforced the involvement of chromosomes 8 and 22 and also indicated frequent rearrangements of chromosomes 7, 14, 18, and 20.

Epithelioid sarcoma of the penis. Clinicopathologic study of a tumor with myogenic features and review of the literature concerning this unusual location

Soft tissue tumors of the penis are uncommon. We report here the clinicopathologic features of a penile epithelioid sarcoma (ES), review the literature concerning this unusual location and focalize our attention on its differentiation. The 34-year-old patient was admitted for abrupt urinary retention due to the growth of a firm and painful plaque on the left side of the shaft, three years previously clinically diagnosed as Peyronie's disease. Magnetic nuclear resonance revealed an infiltrating lesion of both corpora cavernosa. Histology of bioptic fragments showed a nodular malignant spindle and epithelioid cell tumor with focal necrosis and relatively high mitotic rate. Based on the immunohistochemical data (cytokeratin+, vimentin+, EMA+, CD34+, and S100-), the diagnosis of ES was strongly considered. Penectomy was undertaken and the diagnosis confirmed by both light and ultrastructural microscopy. The 22 month follow-up was free of recurrences and metastases. Although not dissimilar from the 10 previously described ES of the penis in terms of natural history and histology, the tumor reported here showed myogenic features as revealed by both immunohistochemistry (immunoreactivity for muscle specific actin) and ultrastructure (intercellular junctions, discontinuous basal lamina, pinocytotic vesicles and thin filaments with intercalated dense bodies). Although previously observed in ES of other sites, this feature has never been established in ES of the penis.

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.

Epithelioid sarcoma with an 18q aberration

Epithelioid sarcoma is a peculiar soft-tissue neoplasm of uncertain origin, which is characterized by an epithelioid morphology of tumor cells coexpressing epithelial (keratin) and nonepithelial (vimentin) antigens. We herein report a new cytogenetic abnormality with der(22)t(18;22)(q11;p11.2) in a case of epithelioid sarcoma that occurred in the elbow of a 75-year-old man. Histologically, the tumor demonstrated a multinodular proliferation of epithelioid cells, with positive immunostaining for keratin, epithelial membrane antigen (EMA), and vimentin. Cultured tumor cells obtained from fresh surgical materials were frozen in plastic ampules and stocked in a liquid nitrogen freezer. Six years after surgery, the cells were recovered from the freezer and utilized for both morphologic and cytogenetic analyses. These cultured cells both before and after the freezing exhibited essentially the same epithelioid morphology and immunophenotypes as those of the original tumor. A chromosome analysis, together with fluorescence in situ hybridization (FISH), demonstrated a 61-67 modal population, and a characteristic clonal abnormality with der(22)t(18;22)(q11;p11.2). Other clonal abnormalities included numerical (-3, -4, +7, -13, -14, -16, -18, +20, -22) and structural (8p+, 9p+, 12p+, i(21q)) aberrations. Some variant clones also demonstrated i(18q). Since the breakpoint at 18q11 is similar to that reported in synovial sarcoma, this finding may support the presence of a histogenetic relationship between epithelioid sarcoma and synovial sarcoma. Our study thus indicates that the storage of frozen cells is useful for both morphologic and cytogenetic analyses of soft tissue tumors.

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.

Epithelioid sarcoma in FNAB smears

FNAB smears of eleven epithelioid sarcomas were reviewed and analysed. Ten cases had a very similar cytomorphologic picture composed predominantly of dissociated epithelioid-like cells with eccentrically placed nuclei. These tumors were clearly malignant but difficult to differentiate morphologically from melanoma, epithelioid leiomiosarcoma, and Schwannoma or adenocarcinoma. One case was composed of spindle cells and was reminiscent of a fibrohistiocytic tumor. Immunocytochemical reactions to vimentin and cytokeratin were performed in six cases on the Papanicolaou stained smears. The reactions to both antigens were positive in all six cases. Ultrastructural characteristics of eight of the tumors are also described. It seems that epithelioid sarcoma has a rather distinct cytomorphologic picture. Taking into consideration clinical data and using also immunocytochemistry, a definitive diagnosis of epithelioid sarcoma can probably be given from FNAB smears.

Epithelioid sarcoma in childhood: An immunohistochemical, electron microscopic, and clinicopathologic study of 11 cases under 15 years of age and review of the literature

Epithelioid sarcoma in a rare tumor and most of the cases occur in young adults. It is rare in childhood. We have been able to obtain data and histologic material for 11 patients with this disease. The primary sites were head and neck in three patients, inguinal region in one, and extremities in seven. The age range of the patients was 12 weeks to 13 years. There was a preponderance of males over females with a ratio of 1.75. The tumors presented with a typical nodular necrotizing pattern. In three cases giant osteoclast-like cells were present. The immunohistochemistry and electron microscopy showed features consistent with previous observations on epithelioid sarcomas. In one case islands of small dark cells noted on light microscopy were surrounded by basal lamina on electron microscopy. The cells inside the nests were undifferentiated. Six tumors studied by flow cytometry were in DNA diploid range. On follow-up, five children are alive and well 2 to 7 years after treatment. Three children died of tumor progression with metastases to lymph nodes and lungs. One child had been diagnosed only recently, and in one the disease has run a protractive course with multiple recurrences. The behavior of these epithelioid sarcomas in children is similar to that seen in adults, the prognosis being dependent on radical tumor surgery preventing recurrent disease. Long-term follow-up is necessary because the tumor may recur many years after the primary tumor was removed.

Immunohistochemical analysis of extracellular matrix components in synovial sarcoma

Little attention has been paid to the composition of the extracellular matrix in synovial sarcoma, a tumour showing both epithelial and mesenchymal phenotypes. As extracellular matrix participates actively in interactions between epithelial and mesenchymal tissues, further knowledge of the pathogenesis of this tumour may be provided by the study of extracellular matrix components. Therefore, we have analysed the immunohistochemical distribution of type I, III, and IV collagen, fibronectin, laminin and tenascin in four cases of synovial sarcoma. The pattern of immunoreactivity for these molecules varied according to the tissue phenotype of the tumour. Mesenchymal tissue labelled mainly for type I and III interstitial collagen and fibronectin. The epithelial component was surrounded by a laminin and type IV collagen-positive basement membrane, but punctate pericellular reactivity for laminin and type IV collagen was also detected among some mesenchymal cells. Tenascin was strongly expressed in the mesenchymal tissue immediately around epithelial structures and weakly or not at all expressed in the monophasic tumours and in mesenchymal tissue distant from epithelial elements in the biphasic tumours. These results suggest some resemblances between synovial sarcoma and the embryonic development of epithelia from mesenchymal cells, providing further support for the concept of an epitheliogenesis from the mesenchyme in these tumours.

Synovial sarcoma. Inter-relationship of the biphasic and monophasic subtypes

In order to assess minimum diagnostic criteria for synovial sarcoma, particularly the monophasic variety, and the inter-relationship between the monophasic and biphasic types, 32 examples were studied histologically, immunohistochemically (26 cases), and ultrastructurally (13 cases). Of the six biphasic synovial sarcomas examined by electron microscopy, the spindle cell component did not show evidence of epithelial differentiation or resemble the epithelial phase, but did appear fibroblastic; no tumor cells transitional between the spindle and epithelial component were evident. In contrast, all of the seven monophasic lesions had ultrastructural growth patterns and some cellular features approximating the epithelial cells of the biphasic variant. In 11 biphasic synovial sarcomas, epithelial membrane antigen was detected in the glandular epithelium of all cases and cytokeratins in eight cases; in no case were these antigens detected in the spindle cell regions of biphasic lesions. Of the 15 monophasic synovial sarcomas, two were positive for cytokeratins and four for epithelial membrane antigen. Thus, the detection of epithelial markers either immunohistochemically or by electron microscopy (or both) should be the minimal diagnostic criteria for monophasic synovial sarcomas. Based on these findings, it is suggested that monophasic synovial sarcomas do not represent the spindle cell or "stromal" phase of biphasic synovial sarcomas, but are a poorly differentiated variant of the latter. As others have suggested, these tumors are, in fact, carcinosarcomas and carcinomas of the soft tissues and the designation synovial sarcoma is inappropriate for this tumor class.

"Chordoid" meningeal tumors in young individuals with peritumoral lymphoplasmacellular infiltrates causing systemic manifestations of the Castleman syndrome. A report of seven cases

Seven young patients ranging in age from 8 to 19 years had surgically removed meningeal neoplasms with a peculiar myxoid-chordoid pattern. The tumors were surrounded by massive polyclonal lymphoplasmacellular infiltrates with follicles and germinal centers. The patients preoperatively manifested iron-resistant hypochromic microcytic anemia, and one of them had dysgammaglobulinemia and stunted growth. After the masses were removed, the blood picture of the patients normalized, and the adolescent with retarded somatic development resumed normal growth, but two patients developed local recurrence with identical histology and again became anemic. It appears that the peritumoral lymphoplasmacellular infiltrates, which in these instances may be regarded as reactive rather than primary cell proliferations, nevertheless brought about the type of systemic manifestations known as the Castleman syndrome, characteristically seen in patients with angiofollicular lymphoid hyperplasia (hamartoma) of soft tissues, or Castleman's tumor. In one of our patients the inflammatory infiltrate extended far into the surroundings of the meningioma, resulting in the erroneous initial diagnosis of "encephalitis" from a needle biopsy of the brain near the tumor.

Epithelioid sarcoma: the spectrum of ultrastructural differentiation in seven immunohistochemically defined cases

Seven epithelioid sarcomas were examined by light and electron microscopy and by immunohistochemical methods for the presence of vimentin and the epithelial markers keratin and epithelial membrane antigen. All the tumors displayed vimentin and both epithelial markers. Electron microscopy showed a spectrum of cellular differentiation from primitive fibrohistiocytic cells to epithelial-type cells with junctions, microvilli, and tonofilaments. Spindle cells showed myofibroblastic and fibroblastic differentiation. Epithelioid sarcoma appears to be a tumor of primitive cells with the potential for mesenchymal and epithelial differentiation, like some embryonic tumors.

Epithelioid sarcoma in children and adolescents. An immunohistochemical study

Six cases of epithelioid sarcoma were studied by conventional light microscopy and immunohistochemistry. The six cases account for 1.4% of the 417 cases of soft tissue sarcoma collected at the Paediatric Tumor Registry, Kiel. The average age of the five male and one female patient was 10.8 years (median: 13 years). Particular clinical findings included the location of the tumours; three were found in the pelvis, two in the head and neck, and one in the hand. Four patients are living without disease, and one patient died of disease three years after diagnosis. Histologically, four of the six tumours revealed multinucleated giant cells. Immunohistochemically using a panel of mono- and polyclonal antibodies all cases stained positively for vimentin, cytokeratin, epithelial membrane antigen (EMA), and human milk fat globulin (HMFG-2). Five cases were positive for neuron specific enolase (NSE), and three stained positively for protein S-100. A positive reaction for alpha-1-antichymotrypsin was noted in two cases. These immunohistochemical findings attest to the multidirectional differentiating capabilities of epithelioid sarcoma and support the concept of derivation from a multipotent mesenchymal stem cell.

Synovial sarcoma: ultrastructural study and immunohistochemical analysis by a combined peroxidase-antiperoxidase/avidin-biotin-peroxidase complex procedure

To analyze the purportedly epithelial features of synovial sarcoma, the antigenic profiles of 20 of these neoplasms (including 12 of the monophasic type) were studied by three different immunohistochemical techniques, and the results were correlated with ultrastructural observations in 10 cases. All of the biphasic tumors were immunoreactive for the epithelial markers epithelial membrane antigen (EMA) and cytokeratin (CK) and also had ultrastructural features of epithelial differentiation. In contrast, only one of five monophasic tumors had electron microscopic features suggestive of epithelial differentiation, but eight of the 12 were immunoreactive for CK or EMA by a procedure combining the peroxidase-antiperoxidase and avidin-biotin-peroxidase complex methods. It is concluded that synovial sarcoma, including the monophasic variant, is a mesenchymal tumor with epithelial features. Immunohistochemical studies are more sensitive than ultrastructural analysis for documenting epithelial differentiation.

Synovial sarcoma: ultrastructural and immunohistochemical features of epithelial differentiation in monophasic and biphasic tumors

Nineteen synovial sarcomas, six biphasic and 13 monophasic tumors, were examined by light and electron microscopy and immunohistochemically for the presence of the epithelial markers keratin and epithelial membrane antigen (EMA). Ultrastructurally, intercellular spaces with processes are present to varying degrees in the spindle cell component of all synovial sarcomas, and junctional specializations occur in most cases. Tumors of the two types differ in their content of external (basal) lamina, which encloses the epithelial component of all biphasic tumors and is detectable in the spindle cell component of two thirds of them, but is absent from the majority of monophasic tumors. Keratin and EMA were demonstrated in both components of all six biphasic tumors. Of the 13 monophasic tumors, keratin was present in nine, EMA in eight, and at least one epithelial marker in ten. Synovial sarcoma is regarded as a distinctive soft tissue tumor with variable epithelial-like differentiation. The use of electron microscopy can increase the specificity of immunohistochemical studies of soft tissue sarcomas and allow more accurate differentiation of monophasic synovial sarcoma from other spindle cell tumors, particularly those that do not express markers.

Intrapulmonary presentation of extraskeletal myxoid chondrosarcoma of the extremity. Report of two cases

Two cases of extraskeletal myxoid chondrosarcoma are reported. The patients presented with metastasis to the lung, 10 years and 2 years, respectively, prior to discovery of the primary neoplasms in the soft tissues of the lower extremities.

A comparative ultrastructural study of chondrosarcoma, chordoid sarcoma, chordoma and chordoma periphericum

The present study is based on electron microscopical examinations of 15 conventional chondrosarcomas, 1 clear cell chondrosarcoma, 3 mesenchymal chondrosarcomas, 2 so-called chordoid sarcomas (extraskeletal myxoid chondrosarcoma), 4 sacrococcygeal chordomas, 2 ecchordoses and 1 neoplasm of tibia with features of a true peripheral chordoma (parachordoma). The neoplastic cells from various types of chondrosarcoma shared a number of features with nonneoplastic chondrocytes as e.g. a well-developed rough endoplasmic reticulum and microvillous cytoplasmic processes. In clear-cell chondrosarcoma, glycogen accumulation in the tumour cells was a prominent feature. The cells of mesenchymal chondrosarcoma usually showed the characteristics of immature mesenchymal cells. In contrast, chordomas commonly contained physaliferous cells with two types of vacuoles in their cytoplasm. The first type can be most adequately characterized as intracytoplasmic pseudoinclusions of intercellular substance, whereas the other type, glycogen-containing, single membrane-bound vacuoles most probably correspond to autophagosomes (cytolysosomes). Only vacuoles of the first type were recorded in the so-called chordoid sarcoma. They were also seen in chondrosarcomas. In contrast, both types of vacuoles were identified in the above-mentioned tibial tumour which, in addition, showed even other cytological characteristics of chordoma. The findings presented here have demonstrated distinct structural relationships between chordoid sarcoma and chondrogenic tumours. On the other hand, our observation of the uncommon tibial neoplasm indicates the possibility that tumours identical with chordoma may occur at sites other than the axial skeleton.

Ultrastructural similarities and differences of synovial sarcoma, epithelioid sarcoma, and clear cell sarcoma of the tendons and aponeuroses

The ultrastructural features of synovial sarcoma, epithelioid sarcoma, and clear cell sarcoma of the tendons and aponeuroses were compared to identify differential markers and similarities. A continuous spectrum of modulation of morphologic features of synovial and epithelioid sarcomas was observed. Biphasic synovial sarcoma with pseudoglandular and stromal components represents one extreme of this spectrum. The gradual disappearance of the pseudoglands and the formation of nests of epithelial-like cells, which are characteristic of epithelioid sarcoma, were observed. The cells of clear cell sarcoma, as well as those of synovial and epithelioid sarcomas, form epithelial-like islands; however, the presence of premelanosomes in the former is a feature of neural crest derivatives.

An assessment of the value of epithelial membrane antigen and other epithelial markers in solving diagnostic problems in tumour histopathology

Using standard immunohistological techniques on formalin-fixed paraffin-embedded sections, we have evaluated the role of epithelial membrane antigen in the histopathological diagnosis of tumours. Of the 70 samples examined, 22 were taken for staging purposes from patients known to have carcinoma and, in half these cases, malignant cells were seen which could not be identified with confidence by conventional means. Forty-eight tumours were stained in order to determine their histogenesis. Twenty-two of these were positive and 20 subsequently proved to be epithelial on follow-up studies, including six in which a diagnosis of non-epithelial malignancy had been made on conventional preparations. The distinction of anaplastic carcinoma from malignant lymphoma and of spindle-cell carcinoma from sarcoma were the most useful applications. One of the positive tumours was of germ cell origin and in one the histogenesis is still not clear. Comparison with carcinoembryonic antigen and pre-keratin showed that epithelial membrane antigen was the most sensitive marker of epithelial differentiation in formalin-fixed tissue. A combination of all three reagents, though, increases diagnostic accuracy and allows tentative suggestions to be made about the possible site of origin of a metastatic carcinoma.

Epithelioid sarcoma: a tumour of myofibroblasts

A case of epithelioid sarcoma of scalp has been studied by light and electron microscopy, histochemistry and immunocytochemistry. The results suggest that epithelioid sarcoma is a tumour of myofibroblasts. The epithelioid appearance results from gross and disordered accumulation of cytoplasmic intermediate filaments (10 nm diameter), possibly of desmin type, producing the misleading light microscopical resemblance to epithelioid histiocytes and biphasic pattern of synovial sarcoma. The cause of the filament accumulation is unknown but it may represent a degenerative change leading to necrosis, a characteristic feature of epithelioid sarcoma.

Monophasic synovial sarcoma of spindle-cell type. Epithelial differentiation as revealed by ultrastructural features, content of prekeratin and binding of peanut agglutinin

Monophasic synovial sarcomas of spindle-cell type and fibrosarcomas were studied by electron and immunofluorescence microscopy for their intermediate filament expression and the binding of peanut agglutinin (PNA). In monophasic synovial sarcomas of spindle-cell type (two cases), frequent cell-to-cell junctions, irregular cytoplasmic processes, and occasional cytoplasmic, tonofilament-like bundles of intermediate filaments were seen by electron microscopy. These features were absent from fibrosarcomas. Immunohistologically, the monophasic synovial sarcomas showed arrays of prekeratin-positive cells in the midst of the vimentin-positive spindle cells. By double fluorescence microscopy, the prekeratin-positive cells also bound PNA, like the epithelial-like cells of the classical biphasic synovial sarcoma. In contrast to monophasic synovial sarcomas, prekeratin-positive cells and arrays of PNA-binding cells, were not seen by immunofluorescence microscopy in fibrosarcomas (seven cases). Thus the prekeratin-content, the binding of PNA lectin, and certain ultrastructural features suggesting early epithelial differentiation, help to distinguish monophasic synovial sarcomas of spindle-cell type from other spindle cell sarcomas.

Experimental tumors with features of malignant histiocytomas. Morphological studies on neoplasms produced by inoculation of an established macrophage-like cell line (WEHI-3)

Soft tissue malignant histiocytomas are thought to be a histologic variant of malignant fibrous histiocytomas. By means of an established macrophage-like cell line (WEHI-3) we produced experimental tumors with light microscopic features of malignant histiocytomas. In spite of repeated subculturing of WEHI-3 cells and their derivatives the 6 tumor generations received by cell transplantations were remarkably constant in regard of their light and electron microscopic morphology. This was in contrast to preceding experiments with an established fibrosarcoma cell line. Electron microscopically they were never to be identified in the histiocytoma-like tumors so that these neoplasms could virtually not be considered as members of the malignant fibrous histiocytoma group. Our results support the idea that malignant fibrous histiocytomas and malignant histiocytomas of the soft tissues arise from undifferentiated mesenchymal cells and emphasize that monocyte-derived histiocytic tumors may appear as soft tissue histiocytomas although they are more related to malignant histiocytosis.

Synovial sarcoma enzyme histochemistry of a typical case

A typical case of biphasic synovial sarcoma was studied using enzyme histochemistry. A marked difference between the staining characteristics of the spindle cells and the epithelial-like cells was demonstrated by reactions for various hydrolytic enzymes. The epithelial-like cells exhibited a strong reactivity for alkaline phosphatase, acid phosphatase, adenosine triphosphatase and nonspecific esterase, whereas spindle-cells were completely unreactive when tested for these enzymes. This is, to our knowledge, the first report demonstrating differences in the enzymatic pattern of the two cell populations which compose synovial sarcoma.