The value of electronmicroscopy and immunohistochemistry in the diagnosis of soft tissue sarcomas: a study of 200 cases

Appearance of recurrent adult fibrosarcoma of the soft tissue and loco-regional post-treatment changes on MRI follow-up

Background

Adult fibrosarcoma (AFS) is a very rare malignant soft tissue tumor, arising from malignant spindle-shaped fibroblasts. We aim to analyze the appearance of recurrent AFS with a focus on configuration and to assess the occurrence of loco-regional post-treatment changes on MRI follow-up.

Methods

One hundred sixty-eight MRI follow-up scans (1.5 T MRI) of 12 patients with histologically proven AFS were reviewed. The recurrent tumors were examined for configuration, limitation, contrast enhancement, and extent and signal intensity on MRI.

Results

The mean age of the patients was 50.2 ± 16.7 years. Forty-two percent of the patients presented recurrent AFS (n = 5). Recurrences occurred 12 ± 6.5 months after tumor resection in the mean. Patients over 55 years of age showed a significantly higher risk for recurrences (RR = 5; 95% CI, 1.8 to 31; p = 0.04). Recurrent AFS was ovoid, nodular, streaky, polycyclic, or fascicular configured with homogeneous/heterogeneous contrast enhancement and well- or ill-defined borders. The intensity of contrast enhancement ranged from rim to marked contrast enhancement. Recurrent AFS mostly showed a muscle iso-intense signal in T1-weighted and a hyperintense signal in PD-weighted/TIRM sequences. The most common post-treatment changes were subcutaneous edema (92%; p = 0.03), muscle edema (75%), and postoperative seroma (50%). Patients with the presence of muscle edema after primary tumor resection had a slightly, but not significantly higher risk for recurrences (RR = 1.75; p = 0.08).

Conclusion

Recurrent AFS shows no common configuration on MRI, as it may appear ovoid, nodular, streaky, polycyclic, or fascicular. Patients with the presence of post-treatment muscle edema have a slightly higher risk for recurrences.

Level of evidence: Level III, therapeutic study

CT and MRI Findings of Soft Tissue Adult Fibrosarcoma in Extremities

OBJECTIVE

To characterize and evaluate CT and MRI features of extremity soft tissue adult fibrosarcoma.

METHODS

CT and MRI images from 10 adult patients with pathologically proven fibrosarcomas were retrospectively analyzed with regard to tumor location, size, number, shape, margins, attenuation, signal intensity, and enhancement patterns on MR images. Additionally, the relationships between lesions, deep fascia, and change in adjacent bones were also assessed.

RESULTS

Nineteen tumor lesions in 10 patients were selected for this study. Eighteen lesions were lobulated and one was oval in shape. Most cases were located under the deep fascia, including seven cases that had a nodular lump adjacent to the deep fascia and one case that had broken lesion through the deep fascia. On CT, the adult fibrosarcomas mostly showed iso-attenuated soft tissue masses (n = 6). On MRI, all the cases (n = 9) displayed low signal on T1-weighted imaging (T1WI) and heterogeneous low and high intensity signals on T2-weighted imaging (T2WI), with band-like areas of low signal on both T1WI and T2WI. On contrast-enhanced MRI images, three cases showed heterogeneous peripheral enhancement and one case demonstrated a spoke-wheel-like enhancement. Eight cases showed muscle edema signals in the peritumoral muscle and one case involved adjacent bone.

CONCLUSION

CT and MR imaging have respective advantages in diagnosing adult fibrosarcoma. Combined application of CT and MR is recommended for patients with suspected adult fibrosarcoma.

Surgical treatment of rare giant malignant tumors of the scalp: A report of 3 cases with different tumor types

The scalp is the most frequent site of occurrence of malignant tumors. As an area that is generally neglected by the patient and not closely monitored during physical examinations, scalp tumors can go unnoticed until they become malignant. The present study reports 3 cases of rare giant malignant tumors of the scalp, namely a peripheral nerve sheath tumor, a fibrous tumor and a malignant proliferating trichilemmal tumor, that were treated at The First Bethune Hospital of Jilin University (Changchun, China). Vascularized free anterolateral thigh flap surgery was performed in 2 of the 3 cases. A local flap repair was applied to the third case. The implanted skin grafts remained viable post-operatively and wound repair was uneventful. No signs of malignancy were detected on the edge of the pathological section upon closer pathological examination. In the follow-up period, no recurrence was detected in any of the cases.

Primary Rhabdomyosarcoma Mimicking a Small Cell Sarcoma of Bone: A Nude Mice Xenograft, Cytogenetic, and Molecular Approach

Small cell sarcomas of bone are difficult to classify and diagnose. The present case deals with such a tumor in which the original biopsy and the resected specimen, studied by histology before chemotherapy, provided no final information about its real nature. Thus several techniques were applied to discern its histogenesis and biology. Myogenin proved positive in isolated cells of the primary neoplasm but was extensively expressed in nude mice xenografts. Electron microscopy confirmed the existence of myofilaments. The cytogenetic analysis revealed a large number of chromo somal abnormalities, but not those found in the Ewing's/PNET (peripheral neuroectodermal tumor) family of tumors. This was confirmed by polymerase chain reaction (RT-PCR) wherein no EWS/Fli 1 or PAX3/FKHR gene rearrangements were detected. Based upon these studies, a rhabdomyosarcoma of bone was diagnosed. Clinically the neoplasm showed a highly aggressive behavior, causing death of the patient within 2 years after diagnosis.

Epithelioid Sarcoma: Diagnostic Features and Genetics

Epithelioid sarcoma (ES) is a rare, aggressive soft-tissue neoplasm of uncertain differentiation, characterized by nodular aggregates of epithelioid cells, which are immunoreactive to cytokeratins (CKs) and epithelial membrane antigen, and often for CD34. It has a propensity for multifocal disease at presentation, local recurrence, and regional metastasis. These are aggressive neoplasms with particularly poor prognosis after regional or distant metastatic disease, for which surgical resection is still the mainstay of treatment, and options for patients with metastatic disease remain undefined. There are 2 distinct variants: classic ES, which typically presents as a subcutaneous or deep dermal mass in the distal extremities of young adults and comprises nodular distributions of relatively uniform epithelioid cells with central necrosis, and the proximal variant, which has a predilection for proximal limbs and limb girdles and the midline of the trunk, which is composed of sheets of larger, more atypical cells with variable rhabdoid morphology. Both classic and proximal-type ESs are associated with the loss of SMARCB1/INI1 protein expression, but appear otherwise molecularly relatively heterogeneous. We review classic and proximal-type ES, discussing morphology, immunohistochemical and genetic findings, the differential diagnosis, and the future potential for targeted therapies.

Practical issues in uterine pathology from banal to bewildering: the remarkable spectrum of smooth muscle neoplasia

Among mesenchymal tumors of the uterus, smooth muscle neoplasms are most common. The wide morphologic spectrum, especially within the category of leiomyomas, is responsible for diagnostic problems more frequently with leiomyosarcoma (including mitotically active, apoplectic, and leiomyoma with bizarre nuclei) but also with endometrial stromal tumors. In the former scenario, clinical information, gross appearance as well as strict utilization of morphologic criteria including cytologic atypia, mitotic activity, and tumor cell necrosis are clues in establishing the correct diagnosis. It is important to keep in mind that mitotic rate thresholds vary for the different subtypes of leiomyosarcoma. Of note, p16 should be used with caution in supporting a diagnosis of leiomyosarcoma as it is often positive in leiomyomas with bizarre nuclei and leiomyomas with apoplectic change (in the latter most frequently and more intense near areas of necrosis). MED12 mutations have also a very limited role in this differential diagnosis. Endometrial stromal tumors are by far, less common than smooth muscle tumors, but can be confused with leiomyosarcomas if they are associated with an undifferentiated uterine sarcoma and the low-grade component is overlooked or they have a myxoid/fibroblastic morphology. The differential diagnosis may be confounded if the latter is associated with a high-grade endometrial stromal sarcoma. It is important to highlight that CD10 is not a reliable marker in these differentials and should be used as a part of a panel of antibodies that also includes desmin and h-caldesmon. Two other recently categorized tumors in the uterus that merit special mention are PEComa and inflammatory myofibroblastic tumor as they enter in the differential diagnosis of smooth muscle tumors. PEComa may be part of the tuberous sclerosis syndrome and may show either a predominantly epithelioid or spindle morphology or combination thereof. Rarely, it may contain melanin pigment. There is variable positivity for HMB-45, MelanA, MiTF, and CathepsinK, and some tumors have been shown to express TFE-3 especially when associated with "clear cell" morphology. Patients with adverse outcome have tumors with ≥2 of the following features: ≥5 cm, infiltration, high-grade cytologic features, mitotic rate ≥1/50 high-power fields, necrosis, or lymphovascular invasion. Inflammatory myofibroblastic tumor is important to recognize as it often mimics myxoid smooth muscle tumors, either benign or malignant. The presence of an associated lymphoplasmacytic infiltrate should alert to that possibility and ALK studies (immunostain or FISH) are helpful in establishing this diagnosis. These tumors can behave in a malignant manner if large, associated with abundant myxoid change, brisk mitotic rate or show tumor cell necrosis.

Synovial sarcoma: defining features and diagnostic evolution

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

Use of immunohistochemical staining and electron microscopy to aid in diagnosis of soft tissue sarcomas associated with the fetlock joint in two horses

Soft tissue sarcomas of the equine distal limb associated with joints, sheaths, or bursae have rarely been reported. Accurate diagnosis of these tumors is challenging in both human beings and veterinary species. Immunohistochemical staining and transmission electron microscopy have been used in human beings to reduce misdiagnosis. The current report describes 2 mature horses presenting with lameness and swelling associated with the dorsal aspect of the metacarpo(tarso)phalangeal joint. In both cases, surgical excision was performed with subsequent histological analysis of the masses to determine the tissue of origin. In both cases, immunohistochemical staining and transmission electron microscopy aided the definitive diagnosis of fibrosarcoma associated with the fetlock joints of 2 horses.

CD133+ subpopulation of the HT1080 human fibrosarcoma cell line exhibits cancer stem-like characteristics

The cancer stem cell (CSC) theory holds that a minority population within tumors possesses stem cell properties of self-renewal and multilineage differentiation capacity and provides the initiating cells from which tumors are derived and sustained. However, verifying the existence of these CSCs has been a significant challenge. The CD133 antigen is a pentaspan membrane glycoprotein proposed to be a CSC marker for cancer-initiating subpopulations in the brain, colon and various other tissues. Here, CD133+ cells were obtained and characterized from the HT1080 cell line to determine the utility of this marker for isolating CSCs from human fibrosarcoma cells. In this study, CD133+ cells were separated from HT1080 cells using magnetic beads and characterized for their proliferation rate and resistance to chemotherapeutic drugs, cisplatin and doxorubicin, by MTS assay. Relative expression of tumor-associated genes Sox2, Oct3/4, Nanog, c-Myc, Bmi-1 and ABCG2 was measured by real-time polymerase chain reaction (PCR). Clonal sphere formation and the ability of CD133+ cells to initiate tumors in BALB/c nude mice was also evaluated. We found that CD133+ cells showed a high proliferation rate, increased resistance to chemotherapy drugs and overexpression of tumor-associated genes compared with these features in CD133- cells. Additionally, CD133+ cells were able to form spherical clusters in serum-free medium with high clonogenic efficiency, indicating a significantly greater tumor-initiating potential when compared with CD133- cells. These findings indicate that CD133+ cells identified within the HT1080 human fibrosarcoma cell line possess many CSC properties and may facilitate the development of improved therapies for fibrosarcoma.

Treatment and outcomes of epithelioid sarcoma of the spine

Epithelioid sarcoma (ES) is a rare soft-tissue neoplasm which is most commonly found in the extremities of young adult males. ES has a poor prognosis due to its aggressiveness as it frequently recurs locally and can undergo lymphatic metastasis to soft tissue, fascia, bone, lymph nodes, lung, and brain. The most common form is the classic-type (granuloma-like), though a more aggressive subtype known as the proximal- or axial-type has also been described. As ES of the spine is exceedingly rare, with only seven patients being reported in the literature, the outcomes of these patients is unclear. We have reviewed the literature of all existing spinal ES cases to recommend treatment strategies and report the first case of proximal-type ES in the cervical spine. Patients with spinal ES had an average age of 20.7 years, with 71.4% of cases being in males. Metastasis was common and was found in 83.3% of patients, with lung metastasis being found in 60% of these patients. Due to the high rates of local recurrence and distant metastasis, the goal of surgery remains gross total resection of all tumor and involved bony elements if feasible without significant neurological deficits. Ligation of involved nerve roots may be necessary to achieve adequate resection of the tumor mass as nerve sheaths can serve as a pathway for extension. In the cervical spine, resection of these lesions is difficult due to involvement of the vertebral arteries in addition to nerve roots, increasing the surgical risk.

Value of ancillary studies in the evaluation of fine-needle aspiration specimens: Our experience

Background:

The cytological diagnosis of poorly differentiated tumors is challenging because the tumor cells may have morphologically difficult presentations in materials obtained by fine-needle aspiration cytology (FNAC). With the application of FNAC in primary diagnosis of malignant lesions, there has been a significant increase in the use of ancillary studies in the aspirated material.

Aims:

We evaluated the value of ancillary studies, namely cell blocks, immunocytochemistry (ICC) and electron microscopy (EM), in the final interpretation of FNAC smears.

Materials and Methods:

Sixty-nine cases of neoplastic swellings were subjected to FNAC. Material acquired was divided for ICC, consisting of immunoperoxidase staining of direct smears, and/or cellblocks and EM, in addition to routine light microscopy (LM). Correlation with the available histological material with immunohistochemistry and/or pertinent clinical information was used as a “gold” standard.

Results:

Five (7.2%) cases were excluded from the study, the material being necrotic or insufficient. Cell blocks were available in 46/64 (71.8%) cases, ICC evaluation was performed in 41/64 cases (64%) and EM studies were done in 57/64 cases (89%). Diagnostic accuracy of LM alone was 32/64 (50%). Cell blocks improved the diagnoses in 8/46 (17%) cases. The ICC data were diagnostic in 18/41 (43.9%) cases, helpful in 8/41 (19.6%) cases and non-helpful in 15/41 (36.5%) cases. EM studies were diagnostic in 22/57 (38.5%) cases, helpful in 18/57 (31.5%) cases and non-helpful in 17/57 (30%) cases. In 34/64 (53.1%) cases, all ancillary techniques (cell blocks, ICC and EM) were applied and their diagnostic accuracy was compared.

Conclusions:

With appropriate case selection, ancillary studies performed on aspirated material can provide useful information in FNAC.

Primary Malignant Fibrous Histiocytoma in Mediastinum: Imaging with (18)F-FDG PET/CT

Malignant fibrous histiocytoma (MFH) is the most common soft tissue tumor which often occurs in the extremities and the retroperitoneum. Primary mediastinal MFH is rare; thus, findings on (18)F-fluorodeoxyglucose positron emission tomography/computed tomography ((18)F-FDG PET/CT) of mediastinal MFH have not been reported yet. We report herein the case of a 64-year-old man who was presented with a superior mediastinal mass. The mass showed intense (18)F-FDG uptake with central metabolic defect on PET/CT. The maximum standardized uptake value was 17.4. After tumor removal via median sternotomy, an MFH of the storiform-pleomorphic type was diagnosed on histopathologic examination. We present the first report of (18)F-FDG PET/CT imaging of MFH in the superior mediastinum.

Some general considerations about the clinicopathologic aspects of soft tissue tumors in children and adolescents

Soft tissue tumors in children and adolescents are an important group of neoplasms, pseudoneoplasms, and tumefactive malformations with some distinctive clinicopathologic, genetic, syndromic, and therapeutic implications. In addition to the basic pathologic examination, there is the availability of diagnostic adjuncts in various settings based upon the histopathologic features that facilitate and/or corroborate a diagnosis. Immunohistochemistry, cytogenetics, molecular genetics, and an ever-increasing array of new technologies are available to address specific diagnostic questions and even potential therapeutic strategies. This review focuses upon some of the unique aspects of soft tissue tumors in children, including the classification, approach to the diagnosis, grading, clinical and pathologic staging, therapy-related changes, pathogenesis, and risk factors.

Immunohistochemistry in diagnosis of soft tissue tumours

Immunohistochemistry in soft tissue tumours, and especially sarcomas, is used to identify differentiation in the neoplastic cells. In some cases, specific antigens are expressed; however, an initial panel of antibodies is often required in order to establish the broad lineage, with a subsequent, more focused, panel to allow classification. Immunohistochemical evaluation must be employed with the clinical picture, the morphology, and, when necessary, other ancillary techniques such as molecular genetics and cytogenetics. Whereas some diagnoses are evident on morphology, many soft tissue neoplasms are seen microscopically as spindle cell, epithelioid cell, small round cell or pleomorphic tumours that need to be further characterized. This article reviews selected applications of immunohistochemistry in the diagnosis of each of the principal morphological groups, concentrating on areas of most use in daily practice.

Transformation potential of bone marrow stromal cells into undifferentiated high-grade pleomorphic sarcoma

PURPOSE

Bone marrow adherent cells contain conventional bone marrow stromal cells and mesenchymal stem cells and these cells constitute the hematopoietic microenvironment. Mesenchymal stem cells have the capacity to give rise to multiple mesenchymal lineage cells and even ectodermal lineage cells. In the present study, we investigated what types of tumor cells are inducible from BM adherent cells by chemical carcinogens.

METHODS

Bone marrow cells from neonatal C3H/HeN mice were collected within 24 h after birth and then cultured. Four days later, bone marrow adherent cells were obtained and the cells were treated with 3-methylcholanthrene.

RESULTS

By this treatment, some transformed clones consisting of large spindle cells were obtained. The transformed cells were highly positive for CD44 and were positive for Sca-1, CD49d and CD106, whereas the cells were negative for hematolymphoid markers. The cell clones had the ability to support hematopoiesis in vitro. These results indicate that the transformed cell lines have the characteristics of BM stromal cells/mesenchymal stem cells. Moreover, during culture of the transformed cells, spontaneous bone nodule formation was observed. When the transformed cells were inoculated into immunodeficient mice subcutaneously, the neoplasms grew in the subcutaneous tissue of the mice. Microscopically and ultrastructurally, the neoplasms showed the typical morphology of undifferentiated high-grade pleomorphic sarcoma (UHGPS). Bone-related genes have been found to be expressed in both transformed cells and UHGPSs.

CONCLUSION

The present study suggests that UHGPSs are derived from BM stromal cells, probably mesenchymal stem cells.

Epithelioid sarcoma

Epithelioid sarcomas are rare, mesenchymal tumors of unknown histogenesis and display multidirectional differentiation, which is predominantly epithelial. They have no normal cellular counterpart and differ from both synovial sarcoma and carcinoma. They account for less than 1% of all soft tissue sarcomas and are usually slow growing, with peak incidence in young adult men and occur predominantly in extremities. Histologically, they form nodules, with central necrosis surrounded by bland, polygonal cells with eosinophilic cytoplasm and peripheral spindling. They regularly express vimentin, cytokeratins, epithelial membrane antigen, and CD34, whereas staining is usually negative with S100, desmin, and FLI-1. Ultrastructurally, they display epithelial and mesenchymal features, including myofibroblastic differentiation. They manifest no specific cytogenetic findings, but several cases have displayed chromosomal abnormalities in 22q region. Clinically, they have a high recurrence rate, and up to 50% of epithelioid sarcomas metastasize. Proximal, fibroma-like, and angiomatoid variants have been described. The proximal variant (with larger cells, prominent nucleoli, and rhabdoid changes) is clinically more aggressive.

Classification and pathology

Soft tissue tumors are a heterogeneous group of benign and malignant processes. Some are assumed to be reactive; others are clearly neoplastic. Because of their rarity, they frequently pose diagnostic problems for surgical pathologists. Accurate diagnosis of these tumors is enhanced by knowledge of the clinical features of the given lesions and, at times, by application of immunohistochemical and molecular techniques. In this article the lesions are described essentially in accordance with the World Health Organization classification.

Aberrant expression of epithelial and neuroendocrine markers in alveolar rhabdomyosarcoma: a potentially serious diagnostic pitfall

Alveolar rhabdomyosarcoma may be extremely difficult to distinguish from other primitive round cell neoplasms without ancillary immunohistochemistry and/or genetic study. Particularly in adults and in the head and neck locations, the differential diagnosis of alveolar rhabdomyosarcoma includes small cell carcinoma and neuroepithelial tumors, such as esthesioneuroblastoma. We have recently seen cases of genetically confirmed alveolar rhabdomyosarcoma, which were misdiagnosed owing to expression of cytokeratins and neuroendocrine markers. We studied a large group of well-characterized alveolar rhabdomyosarcomas for expression of such markers. Forty-four alveolar rhabdomyosarcomas (18 genetically confirmed) were retrieved from our archives and immunostained for wide-spectrum cytokeratin (OSCAR), low molecular weight cytokeratin (Cam5.2), synaptophysin, chromogranin A, and CD56 using commercially available antibodies. Cases were scored as 'negative', 'rare' (<5% positive cells), '1+' (5-25%), '2+' (26-50%) and '3+' (>51%). The tumors occurred in 23 males and 21 females at a mean age of 18 years (range, <1-64 years), and involved many sites. Fifty percent of cases (22 of 44) expressed wide-spectrum cytokeratin, and scored almost equally as rare, 1+, and 2+, but rarely 3+. Cam5.2 was positive in 52% (14 of 27). Forty-three percent of cases (16 of 37) expressed at least one of the specific neuroendocrine markers, 32% (12 of 37) expressed synaptophysin, 22% (eight of 36) expressed chromogranin A, and 11% expressed both. Expression of synaptophysin and chromogranin A was typically confined to rare cells but could be more widespread. Thirty-two percent of cases (12 of 37) expressed the wide-spectrum cytokeratin and at least one of the neuroendocrine markers, and 8% (three of 36) expressed cytokeratin and both neuroendocrine markers. CD56 expression was nearly ubiquitous. Aberrant expression of epithelial and neuroendocrine markers is relatively common in alveolar rhabdomyosarcoma, occurring in 30-40% of cases. These findings have significant implications for the diagnosis of alveolar rhabdomyosarcoma, particularly in adults and in the head and neck locations. Although expression of cytokeratin and/or synaptophysin alone does not necessarily indicate epithelial or neuroendocrine differentiation, coexpression of cytokeratin and neuroendocrine markers, and in particular the presence of chromogranin expression, suggest true epithelial and/or neuroendocrine differentiation in a subset of alveolar rhabdomyosarcomas. CD56 is not a specific neuroendocrine marker, and should not be used in the absence of synaptophysin/chromogranin. These findings emphasize the need to employ a panel of markers, to include desmin, myogenin/MyoD1, and genetic study in the diagnosis of primitive round cell neoplasms in all age groups and in all locations.

The immunohistochemical characterization of devil facial tumor disease (DFTD) in the Tasmanian Devil (Sarcophilus harrisii)

Immunohistochemical techniques were used to characterize the disfiguring and debilitating fatal neoplastic disease, devil facial tumor disease (DFTD), which has recently affected a significant proportion of the wild population of Tasmanian Devils (Sarcophilus harrisii). The diagnostic values of a number of immunohistochemical stains were employed to further characterize 50 representative cases. The neoplasms were negative for cytokeratin (0/48), epithelial membrane antigen (0/42), von Willebrand factor (vWF) (0/11), smooth muscle actin (SMA) (0/26), desmin (0/47), glial fibrillary acid protein (0/13), CD16 (0/13), CD57 (0/43), CD3 (0/18), and LSP1 (0/16). DFTD cells were positive for vimentin (50/50), S-100 (41/48), melan A (11/39), neuron specific enolase (35/35), chromogranin A (12/12) and synaptophysin (29/30). The cells were negative for amyloid (0/30) and stained negatively with Singh's silver (0/34) but were weakly argyrophilic (3/40) using Grimelius histochemical stain. These staining characteristics are consistent with cells of neuroectodermal origin.

The comparative roles of electron microscopy and immunohistochemistry in the diagnosis of soft tissue tumours

Electron microscopy has contributed to the diagnosis of soft tissue tumours for four decades, and immunohistochemistry for two. Because of its relative ease of use and interpretation, the latter technique has become extensively and routinely applied to identify lines of differentiation in benign soft tissue tumours and in sarcomas. The use of electron microscopy has declined but retains a role because few antibodies are wholly specific or fully sensitive, some tumours are polyphenotypic or divergent in differentiation, and others have no specific antigens. Immunohistochemistry is superior in diagnosis of smooth muscle tumours, small round cell tumours, sarcomas with epithelioid morphology, and most synovial sarcomas. Electron microscopy is of particular value for peripheral nerve sheath tumours, marker-negative synovial sarcomas, pleomorphic sarcomas and mesotheliomas. As with all adjunctive techniques, immunohistochemistry and electron microscopy should be used in a complementary fashion according to the nature of the diagnostic problem.

Low-grade malignant perineurioma (perineurial sarcoma) of soft tissue: a potential diagnostic pitfall on fine needle aspiration

A case of low-grade malignant perineurioma presenting as a mass in the thigh is described. The patient was a 76-year-old woman with an enlarging painful mass on her right lateral thigh over the past 2 months. Thorough clinical and radiological studies did not reveal any evidence of tumor elsewhere. The patient underwent fine needle aspiration of the mass, which revealed pleomorphic spindle cells in small clusters or dispersed as single cells within myxoid stroma, cytologically consistent with a high-grade sarcoma. At surgery, the tumor was found to be entirely confined within the muscle. Grossly, the tumor measured 6.5 cm in greatest diameter and showed a gray-white fleshy cut surface that was well circumscribed but unencapsulated. Histologic examination showed a highly cellular spindle cell proliferation embedded within myxoid stroma. The tumor cells showed mild to moderate nuclear pleomorphism with minimal mitotic activity. No evidence of hemorrhage or necrosis was noted. The tumor irregularly invaded the surrounding skeletal muscle. Immunohistochemical studies showed weak membranous positivity for epithelial membrane antigen and focal cytoplasmic positivity for CD34; stains for smooth muscle actin, cytokeratin AE1/AE3, desmin, CD56, H-caldesmon, calponin, and S-100 protein were negative. Electron microscopy showed cells with thin, elongated cytoplasmic processes extending along connective tissue in a parallel, onion-like arrangement and prominent subplasmalemmal pinocytotic activity. The marked pleomorphism displayed on fine needle aspiration observed in this case can lead to a mistaken diagnosis of high-grade sarcoma resulting in unnecessarily aggressive management.

Myofibroblastic malignancies

Malignant tumors composed of myofibroblasts are increasingly being recognized, but their existence remains controversial. Currently accepted examples within this category represent spindle cell or pleomorphic neoplasms of the soft tissues with a spectrum of histological grades. Low- and intermediate-grade myofibrosarcomas are fascicular spindle cell neoplasms resembling fibrosarcoma or leiomyosarcoma. They infiltrate deep soft tissue with disproportionate involvement of head and neck sites and can recur locally but infrequently metastasize. They variably express myoid immunohistochemical markers, and their differential diagnosis includes benign myofibroblastic proliferations such as fasciitis and fibromatosis as well as other types of spindle cell sarcoma. High-grade (pleomorphic) myofibrosarcomas are an ultrastructurally defined subset of malignant fibrous histiocytoma, which they resemble in morphology and behavior. Inflammatory myofibroblastic tumor and infantile fibrosarcoma are neoplasms that have myofibroblastic features and have been included in this category, but they have distinctive genetic findings. This article reviews the concept of myofibrosarcoma and describes its variants.

Myofibrosarcoma

Myofibrosarcomas are malignant tumours of myofibroblasts, which have been recognised for many years, but have become clearly defined only recently. They are low- or high-grade sarcomas that arise in soft tissue or bone in adults or children. Low-grade myofibrosarcomas are infiltrative tumours, usually in deep soft tissue, with a predilection for the head and neck region, which display a range of microscopic appearances from fasciitis-like to fibrosarcoma-like; all cases at least focally display nuclear pleomorphism. They express smooth-muscle actin and calponin, and some express desmin, but most lack h-caldesmon. Low-grade myofibrosarcomas can recur but rarely metastasise. Their differential diagnosis is from benign myofibroblastic proliferations, such as fasciitis and fibromatosis, as well as from fibrosarcoma and leiomyosarcoma. Pleomorphic myofibrosarcomas are high-grade pleomorphic sarcomas (malignant fibrous histiocytoma), which show ultrastructural evidence of myofibroblastic differentiation. They closely resemble malignant fibrous histiocytoma clinically and morphologically, but are more frequently actin positive. This article describes the low- and high-grade variants of myofibrosarcoma and other malignant tumours with myofibroblastic differentiation.

Cerebellar malignant fibrous histiocytoma: case report and literature review

OBJECTIVE AND IMPORTANCE

Malignant fibrous histiocytoma in the central nervous system is uncommon. Fewer than 70 cases have been documented and, to the best of our knowledge, this is the first case arising from the cerebellum.

CLINICAL PRESENTATION

A 44-year-old woman presented with headaches, vomiting, and dizziness. A neurological examination revealed right cerebellar syndrome. Brain computed tomographic scans revealed an isodense tumor in the right cerebellar hemisphere. The breast ultrasonographic, bone scintigraphic, and thoracoabdominal computed tomographic findings were normal.

INTERVENTION

The patient was surgically treated. The tumor recurred 1.5 months later, demonstrating hemorrhagic characteristics on brain computed tomographic scans. The patient underwent a second operation, followed by radiotherapy.

CONCLUSION

Malignant fibrous histiocytoma is still a controversial entity, and the lack of specific criteria means that it must be diagnosed via the process of elimination. With currently available therapy, our review can provide only a very poor prognosis. The median survival time was 27 months. In attempts to develop better therapeutic strategies, total excision and radiotherapy seem to represent the best treatment approach.

Immunohistochemical analysis still has a limited role in the diagnosis of malignant mesothelioma. A study of thirteen antibodies

To identify the most accurate and useful panel to diagnose mesothelioma, we immunostained sections from 112 mesotheliomas, 18 adenocarcinomas, and 11 reactive pleural specimens with 13 antibodies. Positive results for mesotheliomas, adenocarcinomas, and reactive pleura, respectively, were CAM5.2, 111, 18, and 11; vimentin, 30, 3, and 3; HBME-1, 75, 10, and 8; thrombomodulin, 31, 2, and 2; calretinin, 43, 6, and 11; and CD44H, 68, 10, and 4. Positive results for adenocarcinoma markers in mesotheliomas and adenocarcinomas, respectively, were carcinoembryonic antigen, 1 and 15; LeuM1, 7 and 9; and Ber-EP4, 5 and 12. All reactive pleura were negative. Positive results for markers to help distinguish mesothelioma from reactive pleura in mesotheliomas, adenocarcinomas, and reactive pleura, respectively, were epithelial membrane antigen, 76, 17, and 6; p53, 78, 16, and 9; P-170 glycoprotein, 37, 4, and 2; and platelet-derived growth factor receptor beta, 31, 1, and 2. The differential diagnosis of mesothelioma from adenocarcinoma is based on negative markers. Individual mesothelial markers are of low sensitivity and specificity for mesothelioma. However, diagnostic accuracy is improved by the use of antibody panels. To date there are no antibodies that help distinguish mesothelioma from reactive pleura.

Myofibroblastic differentiation in malignant fibrous histiocytoma (pleomorphic myofibrosarcoma): a clinicopathological study

AIMS

We compared the clinical and pathological features of pleomorphic malignant fibrous histiocytoma (MFH)-like soft tissue sarcomas with and without myofibroblastic differentiation on electron microscopy.

METHODS AND RESULTS

Fifty-three soft tissue tumours designated as MFH by light and electron microscopy were reassessed. Eighteen were specifically diagnosed and excluded, and follow-up (FU) information obtained for 24 of the other 35 cases. Myofibroblastic ultrastructure was seen in 7/24 (29%). Seventeen of 24 (71%) lacked myofibroblasts on electron microscopy, which showed fibroblastic or undifferentiated cells. Histologically, all tumours but one had storiform-pleomorphic areas; one myofibroblastic neoplasm was fascicular and myxoid. No other morphological differences were seen. In seven myofibroblastic cases, smooth muscle in four cases and muscle-specific actin in two cases, desmin in three cases and S100 in one case were present. In 15 other tumours, smooth muscle in five cases and muscle-specific actin in one case, and desmin in one case were present; none of these cases expressed S100. CD34 was found in the myxoid areas of one myofibrosarcoma and 3/15 other tumours. Positivity for bcl-2 was seen only in non-myofibroblastic sarcomas (4/14). On follow-up (median 41 months), 2/7 (29%) myofibroblastic tumours recurred, 5/7 (71%) metastasized, and 3/7 (43%) patients died of disease. Among the non-myofibroblastic sarcomas, with a median follow-up of 47 months, 6/17 cases (35%) recurred, 10/17 (59%) metastasized, and 7/17 patients (41%) died of disease.

CONCLUSIONS

Pleomorphic sarcomas with and without myofibroblastic differentiation on electron microscopy are clinically and histologically similar. The former display myoid immunohistochemical markers more frequently.

Myofibrosarcoma: a clinicopathologic study

The concept of soft tissue sarcomas composed predominantly of myofibroblasts has been controversial. We examined a series of such lesions of low- and intermediate-grade malignancy to further define their clinical and pathologic features. Histologic appearances of four cases diagnosed as myofibrosarcoma by electron microscopy were reviewed. Eleven additional cases with similar morphology were then identified from 249 tumors originally indexed as fibrosarcoma. Electron microscopy was performed on five of these, and immunohistochemistry was carried out on all cases for which material was available. There were 11 men and 4 women aged 33 to 73 years (median, 54 yrs; mean, 53 yrs). Lesions mainly involved the head and neck, extremities, and trunk and ranged in size from 1.5 to 12 cm. The tumors were composed of bland or pleomorphic stellate to spindled cells with eosinophilic cytoplasm and tapered nuclei in a collagenous stroma; 10 were grade 1 and five were grade 2. All sarcomas displayed fascicular or storiform patterns, and some of the grade 1 lesions superficially mimicked nodular fasciitis. Electron microscopy of nine cases showed myofibroblastic differentiation, and immunohistochemistry showed smooth muscle actin in 13 of 15 cases, muscle-specific actin in 7 of 9, desmin in 6 of 14, and cytokeratin in 0 of 11. Four of nine grade 1 and three of four grade 2 tumors recurred (one twice), and one grade 2 tumor metastasized to the lungs. Myofibrosarcomas are indolent low-grade or occasionally aggressive intermediate-grade sarcomas which can be recognized by light microscopy. Their clinical importance lies in the resemblance, particularly of low-grade examples, to reactive or pseudosarcomatous conditions.

The continuing value of electron microscopy in surgical pathology

For decades, transmission electron microscopy has played a valuable diagnostic role in surgical pathology. The continuing importance of electron microscopy, however, can be debated, given the major advances that have occurred in immunohistochemistry and other techniques. Electron microscopy retains excellent educational potential and broad research applicability, and it continues to be a necessity for the evaluation of a small subset of surgical pathology cases, such as renal biopsies and cilia specimens. The real controversy, then, centers on the contribution of electron microscopy in the evaluation of neoplasms. The opinion of many experts indicates that electron microscopy is still vital in the diagnostic assessment of some neoplasms, and that both electron microscopy and immunohistochemistry are more powerful when viewed as complementary rather than competitive techniques. For electron microscopy to be used to its potential, however, electron microscopists must function effectively as consultants. When optimally applied, electron microscopy remains an essential diagnostic tool.

Current aspects of the pathology of soft tissue sarcomas

In soft tissue sarcomas, advances in pathological techniques, including immunohistochemistry, cytogenetics, and molecular genetics, have improved diagnostic accuracy, confirmed or clarified interrelationships between tumor subtypes, and revealed mechanisms of tumorigenesis. Many sarcomas are associated with abnormalities of tumor-suppressor genes, and several types have been found to have specific chromosomal translocations. These data and correlative clinicopathologic studies, although confirming many traditional pathological views, enable refinement or reassessment of terminology and classification of some small round cell, spindle cell, pleomorphic, and lipogenic tumors. New factors are emerging for prediction of tumor behavior, which might ultimately relate to therapy once a wider range of treatment options becomes available. This article reviews these current aspects of sarcoma pathology.

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.

Role of electron microscopy and other special techniques in the diagnosis of childhood round cell tumors

A series of case presentations show unique challenges associated with childhood round cell tumors and the role of ancillary techniques in diagnosis. Electron microscopy is shown to be the most powerful individual technique. Immunohistochemistry is less effective but also essential. Other ancillary techniques may provide needed additional diagnostic information. Because this is an area where it is of great importance to secure the most rapid, accurate, and specific diagnosis possible, an integrated multimodal approach is recommended--incorporating light microscopic, electron microscopic, and immunohistochemical studies as a matter of routine, and providing for cytogenetic and/or molecular diagnostic studies as indicated.

Perineurial malignant peripheral nerve sheath tumor (MPNST): a clinicopathologic, immunohistochemical, and ultrastructural study of seven cases

Most malignant peripheral nerve sheath tumors (MPNST) are schwannian in nature. The pathologic features of MPNST with perineurial cell differentiation remain to be characterized. To determine the clinicopathologic, immunohistochemical, and ultrastructural characteristics of perineurial MPNST, 121 MPNST from the Mayo Clinic Tissue Registry were examined. Of these 23 spindle cell tumors with long processes disposed in whorls or storiform patterns, features typical of perineurioma, were studied. On the basis of immunohistochemistry (epithelial membrane antigen+/S-100-), 5 perineurial MPNST were identified among 23 tumors selected. These and two previously characterized perineurial MPNST are the subject of this study. None of seven tumors was associated with NF-1. Patients included five males and two females ranging in age from 11 to 83 years (mean, 45.7 years). The tumors measured 1.5 to 30 cm (mean, 9.1 cm) and arose in the extremities (two), trunk (two), face (one), mediastinum (one), and retroperitoneum (one). Only one tumor was nerve associated (phrenic nerve). All tumors were surgically removed. No encapsulation or neurofibroma components were noted. Necrosis was seen in three lesions. Four tumors were classified as high-grade malignant and three as low grade. Mitotic indices varied from 1 to 85/10 high-power fields (median, 16). Immunoreactivities included epithelial membrane antigen (100%), vimentin (100%), Leu-7 (57%), and CD34 (14%). Stains for S-100 protein, muscle markers, and cytokeratin were nonreactive. Ultrastructurally, perineurial-like cells were noted in three tumors and cells intermediate between perineurial and Schwann cells in one. Four tumors recurred and two metastasized; no deaths of disease were noted at follow-ups of 28 to 98 months (mean, 66.9). In conclusion, 4% of MPNST show perineurial cell differentiation. An NF-1 association has yet to be described. Nerve involvement is infrequent. Their immunophenotype (epithelial membrane antigen+/S-100-) frequently indicates ultrastructural perineurial differentiation. The prognosis of perineural MPNST appears to be more favorable than that of conventional MPNST.

Malignant peripheral nerve sheath tumor of the pancreas with perineurial cell differentiation

The authors report a malignant peripheral nerve sheath tumor (MPNST) that developed in the body of the pancreas of a 76-year-old woman. The well-demarcated tumor, 4.5 x 3.5 cm in size, was composed of spindle-shaped cells arranged in a storiform pattern or sweeping fascicles. Ultrastructurally, the tumor cells had elongated cytoplasmic processes with numerous pinocytotic vesicles, and were covered with discontinuous basal lamina-like substances. Immunohistochemically, tumor cells were diffusely positive for epithelial membrane antigen, vimentin, and CD34, but negative for S-100 protein and Leu 7. It was therefore concluded that the tumor was a MPNST with perineurial cell differentiation. Primary MPNST of the pancreas is extremely rare and the immunohistochemical and ultrastructural studies are necessary for its diagnosis.

Differentiating small round cell sarcomas of the soft parts by an innovative immunogold labeling method: an ultrastructural study

A new immunoelectron microscopy procedure was developed by remaking the fixed-frozen tissue specimens into LR White resin blocks suitable for postembedding colloidal gold immunolabeling, and used to examine 16 cases of small round cell soft tissue sarcomas. In rhabdomyosarcoma, ultrastructural double-immunogold staining demonstrated a coexpression of muscle specific actin and desmin in the same tumor cell. In both Ewing's sarcoma and peripheral neuroepithelioma, the heterogeneous expression of MIC2 gene product (p30/32MIC2) in each tumor cell was demonstrated as well. In peripheral neuroepithelioma, the colloidal gold immunolabeling for neurofilament demonstrated the intermediate filaments surrounding microtubules. The procedure for ultrastructural colloidal gold immunolabeling using fixed-frozen tissue is thus considered to be useful not only for tumor diagnosis, but also for investigating various subcellular structures.

Appraisal of the comparative utility of immunohistochemistry and electron microscopy in the diagnosis of childhood round cell tumors

To provide an objective assessment of the comparative utility of fluorescence- and peroxidase-based immunohistochemistry and electron microscopy, an observer blinded study was conducted under realistic study conditions utilizing a large sampling of poorly differentiated pediatric round cell tumors. Working independently, using a single ancillary technique of particular expertise, each of three investigators attempted to render a specific diagnosis with regard to 50 diagnostically challenging tumors. The results were compared against the subsequent "file diagnosis" established by consensus with all relevant information made available. A grading scheme was applied wherein points were awarded based on the accuracy and confidence of diagnosis. A comparative efficiency rating, expressed as a percentage, was formulated by dividing the number of points awarded each technique by the total number of points theoretically available. Electron microscopy proved superior overall, with an efficiency rating of 89%. Immunoperoxidase and immunofluorescence studies yielded efficiency ratings of 71 and 61%, respectively. Used in combination, the techniques achieved an efficiency rating of 95%. Application of these ancillary techniques resulted in a revision of the provisional diagnosis in 11 of 50 cases, and left only two cases without a firm specific diagnosis.

The management of retroperitoneal soft tissue sarcomas

Over a 5-year period, all retroperitoneal soft tissue sarcomas (119) referred to the Royal Marsden Hospital, London, U.K., were recorded prospectively on a database and managed with a consistent treatment policy. On multivariate analysis, the significant factors responsible for determining prognosis were grade and completeness of excision. Despite improvements in surgical clearance rates (nearly 50% completely excised in this series), the prognosis was poor with 2- and 5-year survival rates of 53 and 20%, respectively. Further improvements in survival rates will depend on better adjuvant treatment.

Variability of differentiation patterns in xenotransplanted spindle cell sarcomas: a histomorphological, immunohistochemical, and ultrastructural study

Three leiomyosarcomas, 3 nerve sheath sarcomas, 1 rhabdomyosarcoma, and 1 sarcoma not otherwise classifiable with 17 of their xenografts, grown on nude mice, were analyzed to assess the degree of concordance between histomorphology, immunohistochemistry, and ultrastructure in spindle cell sarcoma xenograft differentiation. Histomorphology was inconclusive or misleading in 4/8 sarcoma strains and immunohistochemistry in 4/8 originals and in 10/17 xenografts, although specific patterns had been identified ultrastructurally. Electron microscopy was superior to immunohistochemistry and histomorphology in spindle cell sarcoma differential diagnosis. A further purpose of this study was to clarify whether spindle cell sarcoma xenografts retain the morphological characteristics of their primaries. Histomorphological features of the primaries were preserved over all passages, whereas the immunohistochemical marker profiles as well as the ultrastructural phenotypes changed in 14/17 xenografts and in 8/17 xenografts, respectively. Moreover, unusual bidirectional or tridirectional patterns of differentiation were identified ultrastructurally with leiomyomatous as well as Schwann cells occurring side by side and with MFH-like areas in 5/17 xenotransplants. These findings suggest genetic instability of tumor cells and may be important in the consideration of mesenchymal differentiation pathways.

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.

Myofibrosarcoma of the head and neck in children

We have identified a distinctive malignant soft tissue neoplasm that occurred in the head and neck region of six children. Histologically, these neoplasms presented an array of features ranging from low-grade spindle cell to high-grade fibrohistiocytic histologies and often had myoid characteristics. Ultrastructural and immunohistochemical studies indicated that they contained neoplastic myofibroblasts that were variably positive for vimentin (4 positive/4 tested), alpha-smooth muscle actin (4/5), muscle-specific actin (5/5), desmin (2/5), and v-src protein substrate p80/85 (4/5). Three patients died of rapidly progressive unresectable local disease, one died of metastatic and local disease, and two are alive 13 months and 8 years after wide resection. We conclude that these neoplasms form a distinctive subset of pediatric soft tissue sarcomas that display an aggressive clinical behavior, typically with local recurrence, and exhibit features of myofibroblastic differentiation.

Primary pulmonary tumours of nerve sheath origin

Primary intrapulmonary tumours of nerve sheath origin are extremely rare. We describe the clinicopathological features of four such peripheral nerve sheath tumours, two benign and two malignant. Of the benign tumours, one was a typical schwannoma and the other an ancient or degenerated schwannoma. The typical schwannoma was endobronchial in origin, diagnosis being established by small bronchoscopic biopsy. The histological diagnosis of malignant peripheral nerve sheath tumour required immunohistochemical and/or ultrastructural evidence of nerve sheath differentiation. One malignant tumour arose in a patient with Von-Recklinhausen's disease. Both malignant tumours behaved aggressively with the development of multiple intrapulmonary metastases, despite the markedly different histological appearance of the two tumours. Flow cytometric analysis of nuclear DNA content was performed on the four tumours, all of which showed a diploid DNA profile.