B cells are associated with survival and immunotherapy response in sarcoma

Soft-tissue sarcomas represent a heterogeneous group of cancer, with more than 50 histological subtypes1,2. The clinical presentation of patients with different subtypes is often atypical, and responses to therapies such as immune checkpoint blockade vary widely3,4. To explain this clinical variability, here we study gene expression profiles in 608 tumours across subtypes of soft-tissue sarcoma. We establish an immune-based classification on the basis of the composition of the tumour microenvironment and identify five distinct phenotypes: immune-low (A and B), immune-high (D and E), and highly vascularized (C) groups. In situ analysis of an independent validation cohort shows that class E was characterized by the presence of tertiary lymphoid structures that contain T cells and follicular dendritic cells and are particularly rich in B cells. B cells are the strongest prognostic factor even in the context of high or low CD8+ T cells and cytotoxic contents. The class-E group demonstrated improved survival and a high response rate to PD1 blockade with pembrolizumab in a phase 2 clinical trial. Together, this work confirms the immune subtypes in patients with soft-tissue sarcoma, and unravels the potential of B-cell-rich tertiary lymphoid structures to guide clinical decision-making and treatments, which could have broader applications in other diseases.

Comparative study of the National Cancer Institute and French Federation of Cancer Centers Sarcoma Group grading systems in a population of 410 adult patients with soft tissue sarcoma

PURPOSE

Several histologic grading systems have been validated in soft tissue sarcomas (STS), but no system is currently accepted worldwide. The National Cancer Institute (NCI) and French Federation of Cancer Centers Sarcoma Group (FNCLCC) systems were examined comparatively in the same population of patients with STS to determine which system is the best prognosticator with regard to metastasis development and tumor mortality.

PATIENTS AND METHODS

Four hundred ten adult patients with nonmetastatic STS were examined. Histologic grade was established according to the NCI and FNCLCC systems in each case. The prognostic value of both systems was examined using univariate and multivariate (Cox's model) analyses, and special attention was devoted to tumors with discordant grades.

RESULTS

In univariate analysis, both the NCI and FNCLCC systems were of prognostic value to predict metastasis development and tumor mortality. In multivariate analysis, high-grade tumors, irrespective of the system used, size > or = 10 cm, and deep location were found to be independent prognostic factors for the advent of metastases. Tumor grade had a higher predictive value than size or depth, and higher prognostic weight was assigned to the FNCLCC grading system in Cox models. Grade discrepancies were observed in 34.6% of the cases. An increased number of grade 3 STS, a reduced number of grade 2 STS, and a better correlation with overall and metastasis-free survival within subpopulations with discordant grades were observed in favor of the FNCLCC system.

CONCLUSION

The FNCLCC system showed slightly increased ability to predict distant metastasis development and tumor mortality. The use of this system to evaluate STS aggressiveness might be favored.

Predictive value of grade for metastasis development in the main histologic types of adult soft tissue sarcomas: a study of 1240 patients from the French Federation of Cancer Centers Sarcoma Group

BACKGROUND

Histologic grade is said to be the most important prognostic factor in adult soft tissue sarcomas (STS), but most grading systems have been tested in the overall sarcoma group and the predictive value of histologic grade needs to be assessed specifically for each of the histologic categories.

METHODS

From 1980 to 1994, 1240 nonmetastatic patients were entered in the French STS database. The following parameters were studied: patient's age and gender, previous history, tumor location, size and depth, neurovascular or bone involvement (NBI), histologic type and subtype, and grade (the French Federation of Cancer Centers [FNCLCC] system). Median follow-up for the survivors was 88 months; only 5% of patients were lost to follow-up. The authors performed univariate and multivariate analyses for metastasis-free survival for the overall sarcoma group and for every main histologic type.

RESULTS

In order of importance, parameters were respectively retained as independent predictors of metastasis as follows: grade, tumor size, NBI and tumor depth for the overall group, grade and NBI for malignant fibrous histiocytomas (n = 349), tumor size, histologic subtype and grade for liposarcomas (n = 188), NBI, grade and tumor size for leiomyosarcomas (n = 148), grade and NBI for synovial sarcomas (n = 125), grade for unclassified sarcomas (n = 140), and sarcomas of other types (n = 158). No parameter was significant for malignant schwannomas (n = 72) or for rhabdomyosarcomas (n = 60).

CONCLUSION

In this study, histologic grade appeared as an independent predictor of metastasis development in the main histologic types of adult STS, with the exception of malignant schwannomas and rhabdomyosarcomas.

Molecular characterisation of soft tissue tumours: a gene expression study

BACKGROUND

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.

METHODS

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.

FINDINGS

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.

INTERPRETATION

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.

Bone cancers

BACKGROUND

Frequency distribution data for primary bone sarcomas have long been used to provide clues to the diagnosis of bone cancers after their identification in radiographs. Age and skeletal site are often helpful, in addition to specific radiographic features, in narrowing down the probable histologic categories of bone neoplasms before biopsy.

METHODS

Data on 2627 histologically confirmed primary malignant tumors of bone, as collected by the SEER program during the period 1973-1987, were analyzed by age, sex, race, and anatomical site.

RESULTS

Osteosarcoma was the most frequently diagnosed primary sarcoma of bone (35.1%), followed by chondrosarcoma (25.8%), Ewing's sarcoma (16.0%), chordoma (8.4%), and malignant fibrous histiocytoma, including fibrosarcoma (5.6%). The most frequently diagnosed sarcoma of bone in persons younger than age 20 was osteosarcoma, followed by Ewing's sarcoma. Chondrosarcoma was the most frequently diagnosed bone tumor in the population older than age 50. The overall 5-year relative survival rates were as follows: osteosarcoma, 41.0%; chondrosarcoma, 72.7%; Ewing's sarcoma, 41.2%; chordoma, 63.8%; and malignant fibrous histiocytoma, 42.9%. There was an improvement in the survival rates during the period 1973-1987 for patients with chordoma and for white female patients with Ewing's sarcoma. Ewing's sarcoma and chordoma occurred almost exclusively in the white population.

CONCLUSIONS

SEER data provide a unique opportunity to evaluate the incidence and survival rates of bone sarcomas, which are uncommon but highly lethal tumors. The findings from this analysis provide information useful in the diagnosis of these cancers.

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.

Bethesda proposals for classification of nonlymphoid hematopoietic neoplasms in mice

The hematopathology subcommittee of the Mouse Models of Human Cancers Consortium recognized the need for a classification of murine hematopoietic neoplasms that would allow investigators to diagnose lesions as well-defined entities according to accepted criteria. Pathologists and investigators worked cooperatively to develop proposals for the classification of lymphoid and nonlymphoid hematopoietic neoplasms. It is proposed here that nonlymphoid hematopoietic neoplasms of mice be classified in 4 broad categories: nonlymphoid leukemias, nonlymphoid hematopoietic sarcomas, myeloid dysplasias, and myeloid proliferations (nonreactive). Criteria for diagnosis and subclassification of these lesions include peripheral blood findings, cytologic features of hematopoietic tissues, histopathology, immunophenotyping, genetic features, and clinical course. Differences between murine and human lesions are reflected in the terminology and methods used for classification. This classification will be of particular value to investigators seeking to develop, use, and communicate about mouse models of human hematopoietic neoplasms.

Primary sarcomas of the heart

Seventy-five primary sarcomas of the heart were classified by histologic appearance as angiosarcoma (26 cases), undifferentiated sarcoma (18 cases), osteosarcoma (9 cases), fibrosarcoma (6 cases), malignant fibrous histiocytoma (6 cases), leiomyosarcoma (4 cases), myxosarcoma (3 cases), synovial sarcoma (2 cases), and neurofibrosarcoma (1 case). The ages of the patients ranged from 1 to 75 years at the time of presentation (mean, 39 years). Angiosarcomas were predominantly right-sided and osteosarcomas left-sided. Forty patients treated surgically were examined, and survival correlated with clinical and histologic parameters. the survival rate was poor, with a mean of 11 months and median of 6 months. By univariate analysis, the survival rate was more favorable for patients with tumors located on the left side of the heart, without necrosis, with a low mitotic count, and without metastasis at diagnosis. Survival rates were better in patients receiving chemotherapy and radiation therapy. Age, gender, presence of differentiation, and histologic type did not affect prognosis. By multivariate analysis, a low level of mitotic activity and any therapy were the only significant factors affecting survival rate. Immunostaining with commercially available antisera was useful in the diagnosis of sarcoma but not in subclassification of 19 tumors so tested. Although the prognosis for patients with cardiac sarcomas is dismal, histologic grading is useful in predicting outcome, as has been shown for soft tissue sarcomas of other sites.

Classification of rhabdomyosarcomas and related sarcomas. Pathologic aspects and proposal for a new classification--an Intergroup Rhabdomyosarcoma Study

BACKGROUND

There is a need to develop a single prognostically significant classification of rhabdomyosarcomas (RMS) and other related tumors of children, adolescents, and young adults which would be a current guide for their diagnosis, allow valid comparison of outcomes between protocols carried out anywhere in the world, and should enhance recognition of prognostic subsets.

METHOD

Sixteen pathologists from eight pathology groups, representing six countries and several cooperative groups, classified by four histopathologic classification schemes 800 representative tumors of the 999 eligible cases treated on Intergroup Rhabdomyosarcoma Study II. Each tumor was classified according to each of the four systems by each of the pathologists. In addition, two independent subsamples of 200 of the 800 patients were reviewed according to the new system, so that 343 distinct patients were reviewed once, and 57 of these twice.

RESULTS

A study of the survival rates of all subtypes in the sample of 800 patients led to the formation of a new system. This was tested on two independent subsets of 200 of the original cases and found to be reproducible and predictive of outcome by univariate analysis. A multivariate analysis of the 343 patients classified according to the new system indicated that a survival model including pathologic classification and known prognostic factors of primary site, clinical group, and tumor size was significantly better at predicting survival than a model with only the known prognostic factors.

CONCLUSION

This new classification, termed International Classification of Rhabdomyosarcoma (ICR) by the authors, was reproducible and predictive of outcome among patients with differing histologies treated uniformly on the Intergroup Rhabdomyosarcoma II protocols. We believe it should be utilized by all pathologists and cooperative groups to classify rhabdomyosarcomas in order to provide comparability among and within multi-institutional studies.

The 2020 WHO Classification of Tumors of Soft Tissue: Selected Changes and New Entities

Soft tissue tumors are a relatively rare and diagnostically challenging group of neoplasms that can have varying lines of differentiation. Accurate diagnosis is important for appropriate treatment and prognostication. In the 8 years since the publication of the 4th Edition of World Health Organization (WHO) classification of soft tissue tumors, significant advances have been made in our understanding of soft tissue tumor molecular biology and diagnostic criteria. The 5th Edition of the 2020 WHO classification of tumors of soft tissue and bone incorporated these changes. Classification of tumors, in general, but particularly in soft tissue tumors, is increasingly based on the molecular characteristics of tumor types. Understanding tumor molecular genetics improves diagnostic accuracy for tumors that have been difficult to classify on the basis of morphology alone, or that have overlapping morphologic features. In many large hospitals in the United States and Europe, molecular tests on soft tissue tumors are a routine part of diagnosis. Therefore, surgical pathologists should be familiar with newly emerging molecular genetic techniques in clinical settings. In the near future, molecular tests, particularly in soft tissue tumor diagnosis, will become as routine during diagnosis as immunohistochemistry is currently. This new edition provides an updated classification scheme and essential diagnostic criteria for soft tissue tumors. Newly recognized entities and subtypes of existing tumor types, several reclassified tumors, and newly defined molecular and genetic data have been incorporated. Herein, we summarize the updates in the WHO 5th Edition, focusing on major changes in each category of soft tissue tumor, and the newly described tumor entities and subtypes.

Pathology of lung cancer

This article reviews current concepts in pathologic classification of lung cancer based on 1999 World Health Organization (WHO)/International Association for the Study of Lung Cancer (IASLC) classification. Preinvasive lesions including squamous dysplasia/carcinoma in situ, atypical adenomatous hyperplasia and diffuse idiopathic pulmonary neuroendocrine cell hyperplasia are discussed in addition to current concepts of bronchioloalveolar carcinoma and neuroendocrine tumors.

Nationwide incidence of sarcomas and connective tissue tumors of intermediate malignancy over four years using an expert pathology review network

BACKGROUND

Since 2010, nationwide networks of reference centers for sarcomas (RREPS/NETSARC/RESOS) collected and prospectively reviewed all cases of sarcomas and connective tumors of intermediate malignancy (TIM) in France.

METHODS

The nationwide incidence of sarcoma or TIM (2013-2016) was measured using the 2013 WHO classification and confirmed by a second independent review by expert pathologists. Simple clinical characteristics, yearly variations and correlation of incidence with published clinical trials are presented and analyzed.

RESULTS

Over 150 different histological subtypes are reported from the 25172 patients with sarcomas (n = 18712, 74,3%) or TIM (n = 6460, 25.7%), with n = 5838, n = 6153, n = 6654, and n = 6527 yearly cases from 2013 to 2016. Over these 4 years, the yearly incidence of sarcomas and TIM was therefore 70.7 and 24.4 respectively, with a combined incidence of 95.1/106/year, higher than previously reported. GIST, liposarcoma, leiomyosarcomas, undifferentiated sarcomas represented 13%, 13%, 11% and 11% of tumors. Only GIST, as a single entity had a yearly incidence above 10/106/year. There were respectively 30, 64 and 66 different histological subtypes of sarcomas or TIM with an incidence ranging from 10 to 1/106, 1-0.1/106, or < 0.1/106/year respectively. The 2 latter incidence groups represented 21% of the patients with 130 histotypes. Published phase III and phase II clinical trials (p<10-6) are significantly higher with sarcomas subtypes with an incidence above 1/106 per.

CONCLUSIONS

This nationwide registry of sarcoma patients, with exhaustive histology review by sarcoma experts, shows that the incidence of sarcoma and TIM is higher than reported, and that tumors with a very low incidence (1<106/year) are less likely to be included in clinical trials.

Classification and subtype prediction of adult soft tissue sarcoma by functional genomics

Adult soft tissue sarcomas are a heterogeneous group of tumors, including well-described subtypes by histological and genotypic criteria, and pleomorphic tumors typically characterized by non-recurrent genetic aberrations and karyotypic heterogeneity. The latter pose a diagnostic challenge, even to experienced pathologists. We proposed that gene expression profiling in soft tissue sarcoma would identify a genomic-based classification scheme that is useful in diagnosis. RNA samples from 51 pathologically confirmed cases, representing nine different histological subtypes of adult soft tissue sarcoma, were examined using the Affymetrix U95A GeneChip. Statistical tests were performed on experimental groups identified by cluster analysis, to find discriminating genes that could subsequently be applied in a support vector machine algorithm. Synovial sarcomas, round-cell/myxoid liposarcomas, clear-cell sarcomas and gastrointestinal stromal tumors displayed remarkably distinct and homogenous gene expression profiles. Pleomorphic tumors were heterogeneous. Notably, a subset of malignant fibrous histiocytomas, a controversialhistological subtype, was identified as a distinct genomic group. The support vector machine algorithm supported a genomic basis for diagnosis, with both high sensitivity and specificity. In conclusion, we showed gene expression profiling to be useful in classification and diagnosis, providing insights into pathogenesis and pointing to potential new therapeutic targets of soft tissue sarcoma.

Extramedullary myeloid cell tumors. An immunohistochemical and morphologic study of 28 cases

In an attempt to correlate the morphologic and immunophenotypic findings in extramedullary myeloid cell tumors (EMT), we studied 28 cases with a large panel of antibodies using paraffin section immunohistochemistry. A previous or concurrent diagnosis of acute myelogenous leukemia or chronic myelogenous leukemia was made in 25 cases. Six EMT were morphologically classified as well differentiated (WD-EMT), 17 as poorly differentiated (PD-EMT), and five as blastic EMT. The WD-EMT were easily recognized morphologically and displayed a relatively mature myeloid phenotype, with elastase, CD15, and CD68 positivity in all cases. On the other hand, the five blastic-EMT displayed no morphologic evidence of myeloid derivation, were completely negative for CD15, and were weakly positive for elastase in only one case. The PD-EMT, with a morphologic appearance that resembles large cell non-Hodgkin's lymphoma, variably expressed CD15 and elastase. CD68 and lysozyme were present in the majority of PD-EMT, with some variability, but were negative in most blastic-EMT. CD45 (LCA) was detected in 75% of all EMT and CD34 was positive in 36%; neither antigen was significantly associated with a specific morphology. CD30 reactivity was not evident in any case, but slight positive staining was seen with CD20 (L26) in one WD-EMT. CD43 (Leu 22) was the only antibody that was positive in 100% of cases; staining was always intense and widespread. Antimyeloperoxidase (MPO) was positive in all cases but two, both with a blastic morphology. We conclude that (a) an immunohistochemical panel including CD20, CD43, CD68, and MPO can successfully identify the vast majority (96%) of EMT in paraffin sections, and (b) there is an association between morphology and phenotype in these lesions.

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.

Sarcomas and other malignancies of soft tissue, retroperitoneum, peritoneum, pleura, heart, mediastinum, and spleen

BACKGROUND

Malignant neoplasms of the structural tissues, consisting mostly of soft tissue sarcomas, are morphologically diverse and rarely treated for epidemiologic purposes as individual entities. Our understanding to date of the pattern of occurrence of sarcomas is based largely on reports of limited individual clinic experience or case-control studies, each driven by a single hypothesis, and there have been virtually no descriptions according to specific morphologic type.

METHODS

The accumulated coverage of the SEER populations offers an opportunity to correct this deficit. Each of the diagnoses has been reported and coded using a single set of rules and described in relation to the population at risk in terms of age, sex, race, calendar period, anatomic location, and outcome. In addition, each morphologic type has been compared with each of the others with respect to the pattern of occurrence and survival.

RESULTS

For most of the individual morphologic entities, the pattern of occurrence is specific and unlike other patterns. Differences according to anatomic site, age, sex, race, and period-specific survival were found. Partly because of changes in diagnostic criteria over the years, differences in secular trend, other than that for Kaposi's sarcoma, could not be verified. Although some types of sarcoma may have important genetic determinants, there is evidence of environmental causation in others; for some varieties both genetic and environmental factors may operate. There is no evidence of improvements in survival.

CONCLUSIONS

The most likely basis for the observed patterns are morphology-specific differences in etiology and growth phase. Each of the entities should be considered etiologically distinct and should be studied individually whenever possible.

Sarcoma of the breast. A study of 32 patients with reappraisal of classification and therapy

A retrospective clinicopathologic review of 32 patients with mammary sarcoma exclusive of angiosarcoma or lymphoma was performed. For 25 patients with previously untreated lesions, the median tumor diameter was 4 cm and 14 patients had high or intermediate grade lesions. One of 22 patients treated by mastectomy and one of three patients treated by local excision died of sarcoma yielding an actuarial 5-year survival of 91%. None of the 25 patients had received adjuvant chemotherapy and only one treated by mastectomy had post-operative radiation therapy. Seven other patients were referred for treatment of recurrent mammary sarcoma. In this group, median size of the primary tumor was 6 cm and four had high or intermediate grade histology. Tumor control was achieved for only one of five patients with local recurrence and neither of the two with distant metastases. Median survival was 6 months following initiation of treatment for recurrence. Whenever possible breast sarcomas should be classified according to histologic cell type and grade. For lesions not readily classified, the terms unclassified or anaplastic sarcoma should be used. The diagnosis of stromal sarcoma is best reserved for those infrequent sarcomas that can be traced to the specialized periductal and perilobular stroma of the breast. Total mastectomy is recommended for most patients with postoperative radiation therapy indicated when the adequacy of the margin is in doubt. The role of adjuvant chemotherapy in the primary management of mammary sarcoma is yet to be determined.

Aortic intimal sarcoma with embolic metastases

A 46-year-old woman died from massive bowel infarction. At autopsy, a primary sarcoma was found growing along the intimal surface of the aorta at the level of the celiac axis. Tumor emboli were found in distal aortic branches and most abdominal organs. Immunoperoxidase for Factor VIII and electron microscopy (EM) did not support an endothelial origin. EM showed myofibroblastic differentiation. Review of the literature yields an array of diagnostic histologic terms for these tumors, hampering case comparison. The literature does suggest, however, that the clinical presentation of these rare neoplasms correlates nicely with the location and gross morphology of the lesion. We therefore propose a clinicopathologic classification, categorizing the lesions as intimal (obstructive and nonobstructive) and mural. The former are typically pleomorphic sarcomas and are probably of myofibroblastic origin, whereas the latter are usually leiomyosarcomas or fibrosarcomas that probably originate in the media or adventitia.

Primary intracranial sarcomas: histopathological features of 19 cases

Nineteen primary intracranial sarcomas out of a total of about 25,000 brain tumour biopsies are reported. Subtypes included malignant fibrous histiocytoma (6 cases), leiomyosarcoma (3), rhabdomyosarcoma (2), angiosarcoma (2), and one case each of fibrosarcoma, low-grade fibromyxoid sarcoma, malignant ectomesenchymoma, mesenchymal chondrosarcoma, differentiated chondrosarcoma and Ewing's sarcoma. Histological and immunohistochemical features corresponded to those of extracranial sarcomas. Nests of pleomorphic astrocytes mimicking glioma were detected in the five storiform-pleomorphic malignant fibrous histiocytomas. Our results indicate that intracranial sarcomas can be classified like their extracranial counterparts. The low incidence compared with earlier series is related to changes in classification and progress in histogenetic clarification.

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.

Uncemented tumor endoprostheses at the knee: root causes of failure

Although cemented tumor endoprostheses are the most commonly used method for reconstruction of the distal femur or proximal tibia after resection of primary bone tumors, aseptic loosening remains a common complication. Uncemented tumor prostheses may minimize this problem. We investigated the root causes of prosthetic failure for 99 patients with a fixed-hinge, bone-ingrowth Kotz Modular Femur and Tibia Resection System endoprosthesis and compared complications that led to implant failure with results in the literature. Of the 74 distal femoral implants and 25 proximal tibial implants, 25 patients had complications that resulted in prosthetic failure (removal of the prosthesis) at a median of 24.1 (range, 0.8-72.6) months. Failure was caused by prosthesis (n = 18) or oncologic-related (n = 7) complications. However, limb-salvage was possible for 87 of 99 patients. Smaller stem size in the distal femur and longer bone resection length in the proximal tibia were significantly associated with increased risk of prosthetic failure by multivariate analysis. The risk of stem fracture (6 of 99 patients) and infection (10 of 99 patients) was higher than other reports, but aseptic loosening (2 of 99 patients) was uncommon. These results suggest that although the bone-ingrowth surface of this prosthesis leads to a very low aseptic loosening rate, the higher risk of stem fracture and infection must be addressed in future implant designs.

LEVEL OF EVIDENCE

Therapeutic study, level IV-1 (case series).

Contribution of molecular genetic data to the classification of sarcomas

Many sarcomas are characterized by specific recurrent chromosomal translocations which provide powerful diagnostic tumor markers. Since 1992, the genes involved by almost all of these translocations have been cloned, inaugurating a new era in the study of sarcomas. At the biological level, these chromosomal translocations produce highly specific gene fusions, usually encoding aberrant chimeric transcription factors. Clinically, the correlation of these translocation-derived genetic markers and discrete histopathologic entities has been remarkable. Fusion gene detection has confirmed and refined the nosology of several sarcoma groups. The overall effect has been to strengthen certain pathological concepts rather than to revolutionize. The focus of this brief review is the recent impact that the cytogenetic and molecular detection of these translocations has had on sarcoma diagnosis and classification.

Soft-tissue and bone sarcoma histopathology peer review: the frequency of disagreement in diagnosis and the need for second pathology opinions. The Southeastern Cancer Study Group experience

Histopathologic peer review of specimens from 216 consecutive patients with soft-tissue or bone sarcomas on Southeastern Cancer Study Group protocols was performed by a panel of three pathologists. Subtype of sarcoma, degree of confidence in diagnosis, and grade were compared with agreement or disagreement in pathologic opinion from the primary member institution v the pathology review panel. The most common soft-tissue sarcoma was leiomyosarcoma, followed by malignant fibrous histiocytoma, fibrosarcoma, liposarcoma, malignant schwannoma, and rhabdomyosarcoma. There was total agreement between the primary pathologist and reviewer in 66% of cases. However, 12 cases (6%) were considered on review to not be sarcomas. In 27% of cases the subtype of sarcoma was felt to be incorrect by reviewers. Discordant diagnoses were more common when the confidence of the pathologist was less and when the tumor was of higher grade. There was no improvement in frequency of agreement in the second half of the study, despite educational workshops. We conclude that histologic peer review is important in sarcoma studies and is essential in many patients with presumed sarcomas.