Classification Of Soft Tissue Tumors Research Articles

Hemosiderotic fibrohistiocytic lipomatous lesion: Early pleomorphic hyalinizing angiectatic tumor?

Hemosiderotic fibrohistiocytic lipomatous lesion (HFLL) and early pleomorphic hyalinizing angiectatic tumor (PHAT) are characterized histologically by an admixture of fat, moderately cellular fascicles of hemosiderin-laden spindle cells growing in a perivascular, periadipocytic and septal pattern, as well as the presence of macrophages and chronic inflammatory cells. In contrast to a suggested reactive nature of HFLL, PHAT is regarded as a non-metastasizing tumor of uncertain lineage in the recent World Health Organization classification of soft tissue tumors. Reported herein is the case of a 47-year-old woman with an unencapsulated and irregularly circumscribed recurring lesion in the ankle/foot region that developed following ankle distortion and that fulfills histological criteria for both HFLL and early PHAT. In summary, the present case suggests a reactive over-neoplastic nature of HFLL and confirms profound histological similarities with early PHAT. Until more data become available on the biological potential of HFLL/early PHAT, radical surgical excision and follow up of the patient remains the best treatment option.

Atypical Primary Epithelioid Hemangioendothelioma of the Heart

We report an unusual case of primary cardiac epithelioid hemangioendothelioma (EHE) with atypical features, which was treated by orthoptic transplantation with a good outcome for 10 years despite recurrent pulmonary and nodal metastases. EHE is a rare vascular tumor that belongs to the group of malignant proliferations from the new World Health Organization classification of soft tissue tumors. EHE may harbor atypical features that confer a more aggressive course, albeit better than that of conventional angiosarcomas. Histological examination of the primary cardiac tumor revealed a proliferation of large epithelioid tumor cells presenting atypical features and a mitotic index of 3 mitoses per 10 high power fields. In contrast, pulmonary metastases exhibited typical features of EHE, and CD 34 and CD 31 immunostainings strongly stained cytoplasmic vascular lumen. In this report, we illustrate the potential aggressiveness of the atypical variant of EHE and suggest that transplantation might be considered as an alternative therapy in the treatment of EHE of the heart.

The evolving classification of soft tissue tumours: an update based on the new WHO classification

Tumour classifications have become an integral part of modern oncology and, for pathologists, they provide guidelines which facilitate diagnostic and prognostic reproducibility. In many organ systems and most especially over the past decade or so, the World Health Organization (WHO) classifications have become pre-eminent, partly enabled by the timely publication of new "blue books" which now incorporate detailed text and copious illustrations. The new WHO classification of soft tissue tumours was introduced in late 2002 and, because it represents a broad consensus view, it has gained widespread acceptance. This review summarizes the changes, both major and minor, which were introduced and briefly describes the significant number of tumour types which have been first recognized or properly characterized during the past decade. Arguably the four most significant conceptual advances have been: (i) the formal recognition that morphologically benign lesions (such as cutaneous fibrous histiocytoma) may very rarely metastasize; (ii) the general acceptance that most pleomorphic sarcomas can be meaningfully subclassified and that so-called malignant fibrous histiocytoma is not a definable entity, but instead represents a wastebasket of undifferentiated pleomorphic sarcomas, accounting for no more than 5% of adult soft tissue sarcomas; (iii) the acknowledgement that most lesions formerly known as haemangiopericytoma show no evidence of pericytic differentiation and, instead, are fibroblastic in nature and form a morphological continuum with solitary fibrous tumour; and (iv) the increasing appreciation that not only do we not know from which cell type(s) most soft tissue tumours originate (histogenesis) but, for many, we do not recognize their line of differentiation or lineage--hence an increasing number of tumours are placed in the "uncertain differentiation" category.

Classification of pleomorphic sarcomas: where are we now?

Until a decade ago, so-called pleomorphic and storiform malignant fibrous histiocytoma (MFH) represented the most frequently diagnosed sarcoma, accounting for approximately 40% of adult mesenchymal malignancies. However, the latest World Health Organization classification of soft tissue tumours considers MFH a synonym for undifferentiated pleomorphic sarcoma. Historically, the term MFH was introduced in the medical literature in 1963 by Ozzello, O'Brien and Stout, on the basis of the acquisition of phagocytic properties observed in cultured fibroblasts. The existence of MFH as a well-defined clinicopathological entity became rapidly very popular and by the mid 1980s MFH represented the most common sarcoma in adults. With the advent of electron microscopy, immunohistochemistry and molecular genetics, it became clear that the so-called "facultative fibroblast" theory had no scientific grounds and, in 1992, a milestone paper eventually brought attention to the concept that MFH merely represented a morphological pattern shared by a wide variety of poorly differentiated malignant neoplasms, which include specific subtypes of pleomorphic sarcomas. Currently, accurate subclassification of pleomorphic sarcomas is mandatory as it enables recognition of non-sarcomatous lesions as well as pleomorphic neoplasms not associated with aggressive behaviour. Furthermore, as myogenic differentiation predicts aggressive clinical behaviour among pleomorphic sarcomas, precise histotyping allows prognostic stratification of patients.

The Comparative Role of Immunohistochemistry and Electron Microscopy in the Identification of Myogenic Differentiation in Soft Tissue Pleomorphic Sarcomas

There is increasing evidence that histological classification of pleomorphic soft tissue sarcomas is prognostically useful, since a number of studies have provided evidence that myogenic differentiation is associated with a more aggressive clinical behavior. The aim of the current study was to analyze the role of electron microscopy in comparison with immunohistochemistry in the classification of soft tissue pleomorphic sarcomas. Thirty-nine pleomorphic sarcomas of the somatic soft tissues for which material for immunohistochemical and ultrastructural analysis was available were selected for this study. Cases were classified according to the criteria of the WHO classification of soft tissue tumors on the basis of the histologic appearance and of the results of immunohistochemical analysis, and then diagnoses were reconsidered at the light of the results of the ultrastructural analysis. The group of myogenic sarcomas included 13 leiomyosarcomas, 8 myofibrosarcomas, and 1 rhabdomyosarcoma, while the group of nonmyogenic sarcomas included 11 undifferentiated pleomorphic sarcomas/malignant fibrous histiocytomas (MFH), 4 myxofibrosarcomas, and 2 liposarcomas. Overall, there was a good concordance between immunohistochemistry and electron microscopy in recognizing myogenic differentiation in soft tissue pleomorphic sarcomas. Discrepancies included 1 case showing no immunoreactivity for muscle markers, which displayed ultrastructural features allowing reclassification as leiomyosarcoma, and 2 cases initially classified as undifferentiated pleomorphic sarcoma/MFH, which were reclassified as myofibrosarcomas after ultrastructural analysis. Ultrastructural analysis allowed the identification of pleomorphic sarcomas with myofibroblastic phenotype, a category that is not identifiable based on histologic and immunohistochemical profile. Notably, fibronexus junction was identified in tumor cells of 4 pleomorphic myofibrosarcomas, while 2 other lesions showed putative fibronexus junction structures, consisting of electron-dense straight fibrils adjacent to the cell surface, not clearly in continuity with cytoplasmic actin filaments. In conclusion, the results indicate that immunohistochemistry and electron microscopy can usefully complement each other in the classification of soft tissue pleomorphic sarcomas.

Changing concepts in the pathological basis of soft tissue and bone sarcoma treatment

Though soft tissue sarcomas are rare considerable progress has been made in the clinical and biological understanding of these neoplasms. This has led to the launch of a new WHO classification of soft tissue tumours in 2002, which integrate morphological data with tumour specific (cyto-) genetics. Moreover worldwide consensus has grown how to predict clinical behaviour based on a specific grading system and which specific types of tumours seem not to obey these rules. As a consequence entry criteria for multi-institute prospective trials have changed over the last few years. The recent identification of tumour specific drug targets by immunohistochemistry has had impact on specimen requirements and handling as well as laboratory standards. These changes in concepts, classification, and processing of soft tissue sarcomas have had impact on patient selection and treatment and formats of multi-institute trials.

Role of Microarray in Cancer Diagnosis

Current cancer diagnosis and classification relies on clinical and histopathological information. However, some cases bring diagnostic confusion due to incomplete clinical information and atypical histopathologic features, together with the fact that criteria for histopathologic information is subjective. Molecular diagnosis using tumor biomarkers offers precise and objective tumor diagnosis. Chromosomal changes and genetic mutations can be used in the molecular diagnosis of tumors. Loss of the long arm of chromosome 14 and activating mutation of c-kit are objective genetic changes in gastrointestinal stromal tumors (1-3), and gene rearrangement of bcr/abl is a diagnostic marker for acute myelogenous leukemia (4). However, molecular diagnosis is not generally accepted because of the scant number of objective tumor markers. Moreover, most of the genetic changes are not specific enough to accurately diagnose the tumors and comprehensive mutation databases for the tumors have not been explored (5). Recently, DNA micro-array-based tumor gene expression profiles have been developed and used in the tumor diagnosis and classification. Many studies have demonstrated that a subset of genes is characteristically expressed in ovarian cancers (6), oral cancers (7), melanomas (8), colorectal carcinomas (9,10) and prostate carcinomas (11,12). Molecular classifications using DNA micro-array is useful for the determination of primary sites in metastatic carcinomas (13) and the classification of soft tissue sarcomas (14). Gene expression profiles by DNA microarray analysis show remarkable intertumoral variations in the same histologic type of tumors. These intertumoral variations can be used for precise molecular classifications and can provide opportunities for the evaluation of genetic changes. Gene expression profiles can successfully differentiate the type of leukemia (15) and the oncogenetic pathway for the T-cell leukemia (16). Additionally, several studies have demonstrated a subset of genes representing different genetic and biological changes in solid tumors. Hereditary breast carcinomas differed in germline mutation status of BRCA1 or BRCA2 (17), and hence, prognosis-related molecular classifications were possible in prostate carcinomas (12), lymphomas (18), and gastric carcinomas (19). Although DNA micro-array analysis for tumor diagnosis and classification is a promising diagnostic modality for the future, currently, there are many limitations. First of all, accurate diagnoses of individual tumors by gene expression profile alone are not always possible. This may be because no reference databases for comprehensive gene expression for cancer has been explored, and no specific group of biomarkers for the diagnosis of specific tumors have yet been developed. Secondly, the gene expression data shows remarkable variations within the same tumor. This may result from different gene expression profiles in the tumors and the different peritumoral lymphoid or stromal reaction status. Thirdly, early tumor detection is not possible by the gene expression profile. Currently, cancer diagnosis with the DNA micro-array is possible only when large amounts and high fractions of tumor cells are prepared. Detection of the membrane protein fragments or specific mutations in circulating tumor cells from body fluids is more effective and a popular approach in the early detection of tumors. The analysis of cancer specific mRNAs from body fluids containing tumor cells is another promising way; however, this can be more effectively carried out by RT-PCR (20,21) han by DNA micro-array. In spite of these limitations, DNA microarray can be best used for molecular classification based on genetic and biological changes. In this month's issue, Bae et al (22). reported gene expression profiling of uterine leiomyomas. The authors analyzed the gene expression profiles of leiomyomas by using the cDNA micro-array. They compared the gene expression profile of leiomyomas to that of normal myometrium and found 21 up-regulated and 50 down-regulated genes. Interestingly, most of the up-regulated genes were ones known to have nucleic acid binding activity. This study is a good model for the evaluation of genes involved in multi-step carcinogenesis. The uterine myometrium is mostly composed of homogeneous myometrial cells, and leiomyoma is also a homogeneous tumor originating from myometrial cells. Moreover, leiomyosarcoma is another homogeneous mesenchymal tumor originating from myometrial cells, thus eliminating the heterogeneous peritumoral reaction. This unusual homogeneity of research materials enables one to find many valuable target genes by expression proteomics analysis. It has been reported that DNA micro-array analysis can be a new method for the classification of soft tissue tumors (14). This method can further improve the method based on histological findings. Specific expression of target genes, such as KIT expression in gastrointestinal stromal tumors, was noted within gene sets that distinguished different soft tissue tumors. DNA micro-array analysis for the multi-step model of malignant transformation in soft tissue tumors, such as leiomyomas and leimyosarcomas, will give important information for genes involved in malignant transformation of soft tissue tumors.

Actin isoform pattern expression: a tool for the diagnosis and biological characterization of human rhabdomyosarcoma.

The diagnosis and characterization of rhabdomyosarcoma requires the use of combined histological and immunohistochemical criteria due to the variety of its histological patterns. The identification of actin isoform expression is accepted as a useful adjunct to the diagnosis and classification of soft tissue tumors. Using a new antibody specific for alpha-cardiac actin, obtained according to a recently described strategy for the production of polyclonal antibodies against actin isoforms [9], we have analyzed a series of 17 rhabdomyosarcomas, including all histological subtypes. In addition, we have evaluated the presence in these tumors of alpha-skeletal and alpha-smooth muscle actins. All specimens examined revealed a positive immunostaining for alpha-cardiac actin. Tumoral cells of eight cases also expressed alpha-smooth muscle actin and only three cases (all embryonal subtypes) were positive for alpha-skeletal actin. Our results indicate that immunohistochemical screening for alpha-cardiac actin expression is a useful tool for the diagnosis of rhabdomyosarcoma. They also suggest that the expression of alpha-skeletal actin is valuable in determining the subtype and possibly the state of differentiation of these tumors.

Molecular characterisation of soft tissue tumours: a gene expression study

Soft-tissue tumours are derived from mesenchymal cells such as fibroblasts, muscle cells, or adipocytes, but for many such tumours the histogenesis is controversial. We aimed to start molecular characterisation of these rare neoplasms and to do a genome-wide search for new diagnostic markers. We analysed gene-expression patterns of 41 soft-tissue tumours with spotted cDNA microarrays. After removal of errors introduced by use of different microarray batches, the expression patterns of 5520 genes that were well defined were used to separate tumours into discrete groups by hierarchical clustering and singular value decomposition. Synovial sarcomas, gastrointestinal stromal tumours, neural tumours, and a subset of the leiomyosarcomas, showed strikingly distinct gene-expression patterns. Other tumour categories--malignant fibrous histiocytoma, liposarcoma, and the remaining leiomyosarcomas--shared molecular profiles that were not predicted by histological features or immunohistochemistry. Strong expression of known genes, such as KIT in gastrointestinal stromal tumours, was noted within gene sets that distinguished the different sarcomas. However, many uncharacterised genes also contributed to the distinction between tumour types. These results suggest a new method for classification of soft-tissue tumours, which could improve on the method based on histological findings. Large numbers of uncharacterised genes contributed to distinctions between the tumours, and some of these could be useful markers for diagnosis, have prognostic significance, or prove possible targets for treatment.

Recent progress in the classification of soft tissue tumors: role of genetics and clinical implications

Soft tissue tumors comprise a vast and heterogeneous group of neoplasms. Because different tumors often have different biological behaviors and respond differently to various therapeutic modalities, precise classification is paramount. The majority of soft tissue tumors were first delineated on the basis of morphologic and clinical findings, which in many cases were adequate to accurately separate different tumors into homogeneous groups; however, it has increasingly been appreciated that many entities are actually heterogeneous groups of tumors that have similar histologic and pathologic characteristics but differ in their clinical behavior and underlying pathogenesis. Within the past several years, great strides have been made in the purification of different entities. This accomplishment has largely been because of advances in our understanding of the molecular genetics that underlie the pathogenesis of many sarcomas and the development of new and specific tumor markers. This review highlights some important recent work in two selected soft tissue tumors-gastrointestinal stromal tumor and inflammatory myofibroblastic tumor. These examples illustrate the type of progress that is being made in the classification of soft tissue tumors.

Skin lesions of fibrocytic and fibrohistiocytic differentiation: a new concept and classification.

The WHO classification of soft-tissue tumours derives from an article in a fascicle of the AFIP atlas in 1953 by Arthur Purdy Stout [1], the leading specialist on soft-tissue neoplasia at that time, and was later modified several times. Its current version [2] differentiates entities according to their histopathological derivation into 15 different groups, among them fibrous and fibrohistiocytic tumours, and further subdivides both of these according to their biological behaviour into benign, intermediate, and malignant lesions (Table 1). However, there are great difficulties with this classification, for several reasons.KeywordsFibrous HistiocytomaSolitary Fibrous TumourTendon SheathCollagen BundleNodular FasciitisThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

New diagnostic modalities in soft tissue sarcoma.

Molecular and cytogenetic analysis of soft tissue sarcoma has provided a vast amount of new genetic information over the past 10 years. Recent advances in genetic technology, such as fluorescence in situ hybridization (FISH), reverse transcriptase-polymerase chain reaction (RT-PCR), and positional cloning techniques have greatly increased the rate of new discoveries and soon may bring cytogenetic and molecular analysis to standard pathology laboratories. Karotypic analysis of soft tissue tumors have demonstrated specific cytogenetic aberrations which have proved to be extremely useful diagnostically and have solidified and improved soft tissue tumor classification systems. Objective and reproducible prognostication in soft tissue sarcoma remains problematic. Presently, the grade and size of the sarcoma are the most important factors used to estimate risk of relapse and overall survival. Assigning a pathologic grade to an individual sarcoma as a means of predicting clinical behavior is often difficult with a 40% discordance rate even between expert sarcoma pathologists. There is mounting evidence that the composition of membrane phospholipid in tumor tissue is an important indicator of a tumor's cellularity, proliferative capacity, and differentiation state. However, there is a lack of information on the biochemical determinants of sarcoma proliferation and differentiation. To address these problems, novel quantitative ex vivo nuclear magnetic resonance (NMR) methods have been applied to determine the biochemical changes in tissue lipid for soft tissue sarcoma. The biochemical changes in tissue lipid have been found to correlate with sarcoma cellularity, growth rate, and differentiation. Continued prospective NMR analysis of tissue lipid biochemistry in soft tissue tumors will permit the development of a clinically relevant biochemical system of prognostic determinants for soft tissue sarcoma in the future.

The role of cytogenetics in the classification of soft tissue tumours.

Soft tissue tumours represent a heterogeneous group of mesenchymal lesions, and their classification is the subject of continuous debate. Chromosome analysis, molecular cytogenetics and molecular assays may become increasingly useful in diagnosis, and this review summarises advances in the cytogenetic characterisation and classification of soft tissue tumours. Among the group of fibrous lesions, superficial fibromatosis exhibits trisomy 8. This genomic change is also observed in desmoid fibromatosis in association with trisomy 20. Trisomy 11 is the most frequently observed chromosomal aberration in congenital fibrosarcoma. Dermatofibrosarcoma protuberans and giant cell fibroblastoma share a translocation t(17;22), which supports the concept of the existence of a common differentiation pathway. Adipose tissue tumours is the group in which integration of genetics and pathology has been most fruitful. Ordinary lipomas cytogenetically show an abnormal karyotype in about half the cases. Genomic changes of the 11q13 region are observed in hibernoma. Lipoblastoma exhibits a specific 8q rearrangement in 8q11-q13. Loss of material from the region 16q13-qter and 13q deletions are observed in spindle cell/pleomorphic lipomas. The well-differentiated liposarcoma/atypical lipoma group is characterised karyotypically by the presence of one extra ring and/or extra giant chromosome marker. Myxoid and round cell liposarcoma share the same characteristic chromosome change: t(12;16)(q13;p11) in most cases. In the group of smooth muscle lesions most data are derived from uterine leiomyomas, which can be subclassified cytogenetically into seven different types. Half of all leiomyomas are chromosomally normal; the other half have one of six possible consistent chromosome changes. Alveolar rhabdomyosarcoma is characterised cytogenetically by two variant translocations t(2;13)(q35;q14) and t(1;13)(p36;q14). Among tenosynovial tumours, the localised type of giant cell tumour of tendon sheath exhibits two different karyotypic changes. One involves 1p11 in a translocation with chromosome 2 or with another chromosome. A second type involves 16q24. Synovial sarcoma is characterised cytogenetically by a translocation occurring between chromosome 18 and presumably two adjacent loci on the X chromosome. In neural tumours, abnormalities of chromosome 22 have been reported in benign schwannomas and perineuriomas. Malignant peripheral nerve sheath tumours exist in two main forms: sporadic and associated with the NF-1 syndrome. Karyotypes are very complex, but chromosomes 17q and 22q are very often involved. Clear cell sarcoma is characterised cytogenetically and molecularly by a translocation t(12;22)(q13;q12). The Ewing's sarcoma/peripheral neuroectodermal tumour category shows a central karyotypic anomaly represented by the translocation t(11;22). The two variants t(21;22) and t(7;22) are found in some cases. Among cartilaginous lesion, the most frequently described anomaly is the t(9;22)(q22;q12) in extraskeletal myxoid chondrosarcoma. Intra-abdominal desmoplastic small round cell tumour is characterised by a t(11;22)(p13;q12).

Malignant fibrous histiocytoma: a "fibrohistiocytic" or primitive, fibroblastic sarcoma.

Synchronously with the acceptance of fibrohistiocytic tumors, especially of malignant fibrous histiocytoma (MFH) as a tumor type in the second edition of the WHO classification of soft tissue tumors (Weiss 1993), there is increasing criticism of MFH as an entity (Donhuijsen et al. 1987; Dehner 1988; Fletcher 1992). MFH of the bone was questioned as an entity already years ago (Dahlin et al. 1977). MFH as a sarcoma type became popular during 1960s among Stout and his co-workers (Ozello et al. 1963; O’Brien and Stout 1964; Stout and Lattes 1967). MFH was described as being characteristically composed of two cell types: (a) roundish or polygonal — histiocyte-like; and (b) spindly — fibroblast-like. Varying number of multinu-cleated giant cells, with or without atypia, may be admixed. Collagenous or mucoid intercellular substances vary intralesionally and interlesionally. A whorly cellular arrangement, called “storiform pattern,” was thought to be an important differential diagnostic criterion for MFH — even if not ubiquitous (Meister et al. 179; Enzinger 1986).KeywordsSoft Tissue TumorMalignant Peripheral Nerve Sheath TumorMalignant Fibrous HistiocytomaFibrous HistiocytomaMyxoid LiposarcomaThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Involvement of chromosome 12 in well differentiated liposarcoma

It is well known that “accurate classification of a given tumor is often not easy, so much that acknowledged international experts are still unable to pin a label on about 10% of sarcomas”(Fletcher 1990). In this context, the characterization of new tumor markers is of paramount interest for the diagnosis, prognosis, and classification of soft tissue tumors (Sandberg and Turc-Carel 1987; Molenaar et al. 1989; Fletcher et al. 1991).

Mesenchymal, IMon‐Meningothelial Tumors of the Central Nervous System

The spectrum of non-meningothelial mesenchymal tumors that may arise within the central nervous system is presented, based on the current classification of soft tissue tumors. Among malignant types, hemangiopericytoma, rhabdomyosarcoma, mesenchymal chondrosarcoma, and malignant fibrous histiocytoma are the most frequent ones. Rare tumor entities are mentioned. As in soft tissue sarcomas, diagnosis is mainly based on light and electron microscopy, while immunohistochemistry can improve accuracy of diagnosis.

Malignant Fibrous Histiocytoma: History, Histology, Histogenesis

At the XVI. International Congress of the International Academy of Pathology (Vienna, 1986), a session was dedicated to the classification of soft tissue tumors. At this occasion a critical review of malignant fibrous histiocytoma (MFH) was presented. A) The history of MFH revealed that this tumor had been known for many years under a variety of names. Moreover, MFH apparently had frequently been misinterpreted as other tumor types, as for instance rhabdomyosarcoma. Today, there is a discrepancy between the high incidence of MFH among soft tissue sarcomas and its underrepresentation in some widely used tumor classifications. B) The histological appearance may be fully developed and typical for MFH. However, it also may be merely compatible with MFH in less typical tumor areas. Regional differences in morphological appearance may be pronounced. Differential diagnosis can be helped by histochemical methods. C) Histochemical methods--among others--also help to shed light on the histogenesis. More recent findings point to MFH, as a tumor of fibroblasts rather than histiocytes with similarities to loose areolar connective tissue. Although MFH-like areas may occur focally within a variety of different tumors, there remains a large group of sarcomas which do not display any signs of further differentiation even after careful work-up. In these cases the application of the term MFH, as it is understood today, appears to be justified.

Benign Mesenchymoma of the Tongue

THIS is a case report of an unusual growth situated at the base of the tongue in an infant. The tumor is called a benign mesenchymoma. This type of growth is infrequently encountered in children and certainly the base of the tongue is an unusual site. The term mesenchymoma has, as far as we know, never been mentioned in the otolaryngological literature and when the diagnosis was reported to us, we immediately had to search for texts and articles that described this tumor. When the word mesenchymoma was mentioned to a number of colleagues, it created exclamations of surprise and of ignorance as to the meaning of the term. It is therefore considered proper to bring this case to your attention. A mesenchymoma is a mixed tumor of mesenchymal elements. While this designation had been used before, Stout in his classification of soft tissue tumors defined and advocated the use