Cases Of Angiomatoid Fibrous Histiocytoma Research Articles

Clinical and pathological analyses of 14 cases of angiomatoid fibrous histiocytoma.

Angiomatoid fibrous histiocytoma (AFH) is a soft tissue tumor of uncertain differentiation. Although its prognosis is good, its diagnosis and differential diagnosis remain a challenge, particularly for tumors with an atypical morphology. We evaluated the clinicopathological characteristics of 14 AFH cases and examined the key factors in its diagnosis or differential diagnosis. The cohort comprised 6 men and 8 women aged 9-65years (average age: 31.2years). Most of the tumors (11/14, 79%) were located in soft tissues, whereas 3/14 (21%) were located in the lung (1 case) and brain (2 cases). Tumor cells were spindle-shaped to epithelioid, with a visible fibrous capsule (9/14, 64%), hemorrhagic gap (9/14, 64%), lymphocyte sleeve (7/14, 50%), necrosis (3/14, 21%), and infiltrative boundary (4/14, 29%). The tumors expressed desmin (10/14, 71%) and exhibited low levels of Ki-67. 13 cases (93%) displayed ESWSR1 gene rearrangement. At follow-up, 1 case (7%) experienced local tumor recurrence. AFH is a rare intermediate tumor. Its pathological diagnosis requires a comprehensive analysis of histological, immunophenotypic, and molecular genetic features to avoid misdiagnosis. Our study has further enriched the histological features of AFH, emphasizing the importance of differential diagnosis and providing a reference for clinical practice.

Expanding the spectrum of neoplasms harboring EWSR1:CREM fusion as detected by a real-world clinical genomics platform.

e15061 Background: Malignancies with various well-defined phenotypes and prognoses have been shown to possess gene fusions between Ewing Sarcoma Breakpoint Region 1 ( EWSR1) and one of the CREB family genes, specifically CREB1 and ATF1. However, less is known about neoplasms that harbor EWSR1:CREM rearrangements, which are thought to result in constitutive activation of CREM and subsequent dysregulation of oncogenes, such as BCL-2 family genes, EGFR1, and cyclins. EWSR1:CREM fusion has been identified in rare cases of angiomatoid fibrous histiocytoma, clear cell sarcoma, hyalinizing clear cell carcinoma of the head and neck, and intracranial myxoid mesenchymal tumor. Our study represents the largest to date and seeks to expand and further define the diversity of tumor subtypes that possess EWSR1:CREM fusions. Methods: Detection of EWSR1:CREM rearrangements by whole transcriptome sequencing was performed for > 240,000 neoplasms submitted to Caris Life Sciences (Phoenix, AZ). Histological review of the identified tumors was performed by two board-certified pathologists (MGE, AER). Treatment and outcome information were collected, where available. Results: An EWSR1:CREM fusion was detected in 18 cases, which included one intracranial myxoid mesenchymal tumor, one mesothelioma, four hyalinizing clear cell carcinomas of the head and neck, two clear cell sarcomas, two small round and spindle cell sarcomas, and eight histologically malignant tumors having an epithelioid morphology. While the latter were in keeping with a disease entity recently reported in the medical literature (epithelioid neoplasm with predilection for mesothelial-lined cavities), several of these cases demonstrated unexpected neuroendocrine differentiation and were found at unusual sites, including the kidney, uterus, and cervical spine. Moreover, three cases had the features of squamous cell carcinoma. Surgical resection was performed in all patients, and pazopanib was utilized in two round and spindle cell sarcoma cases. This medication was shown radiographically to produce a partial response at 19 months and stable disease at 26 months, respectively, in heavily pretreated patients. Conclusions: By detecting an EWSR1:CREM rearrangement, molecular testing may aid in the diagnosis of a variety of rare tumor types, including a poorly understood malignant epithelioid neoplasm that arises in a variety of anatomic sites including mesothelial-lined cavities. Tumors harboring this fusion may ultimately be susceptible to treatment with tyrosine kinase inhibitor targeted therapy.

An unusual histopathologic feature of angiomatoid fibrous histiocytoma – A case report and molecular study

Abstract Angiomatoid fibrous histiocytoma (AFH) is a rare soft tissue tumor with intermediate malignant potential. It predominantly affects children and young adults and is most often located in the extremities. The atypical pattern of AFH may create significant diagnostic difficulty. We present a case of AFH diagnosed via molecular confirmation by fluorescence in situ hybridization (FISH) and also review cases of AFH with atypical histologic presentations in Taiwan. We present this case to remind clinicians that identification of gene fusions by molecular testing is a valuable diagnostic tool for AFHs, especially in cases with atypical histopathological presentations.

Intracranial Angiomatoid Fibrous Histiocytoma: Case Report and Literature Review

Angiomatoid fibrous histiocytoma (AFH) is a rare and low-grade soft tissue lesion that typically arises from subcutaneous and deep dermal tissue of extremities. The first case was reported in 1979 by Enzinger and has since become known as a distinct entity. AFH has been increasingly reported in different organ systems, with rare reports of primary intracranial AFH. To date there have been 3 reports of intracranial AFH and 1 report of metastasis to the brain, most of which were in young adults. In this paper, we present a case of an older patient with a large, petrous apex AFH that was clinically mistaken for a trigeminal nerve schwannoma. We discuss radiographic and histologic features initially found and the findings that ultimately led to the diagnosis of AFH. We also discuss the findings noted in all other reports of intracranial AFH. We present a rare case of intracranial AFH in a patient relatively old for onset of diagnosis. To date, only 3 prior cases of AFH have been reported. The radiographic findings were nonspecific and initially pointed toward a diagnosis of schwannoma, whereas histopathology seemed to initially suggest meningioma. Further pathologic consultation finally confirmed AFH as the diagnosis. We suspect there are more cases of intracranial AFH that are misdiagnosed due to variability of findings on pathology. The behavior of this tumor remains in question as 1 of the 3 reported cases demonstrated significant recurrence. As such, gross total resection of this lesion is preferable.

Angiomatoid fibrous histiocytoma: Clinicopathological spectrum of five cases, including EWSR1-CREB1 positive result in a single case.

Angiomatoid fibrous histiocytoma (AFH) is an unusual soft tissue tumor (STT), characterized by recurrences, but rarely metastasis. Later, certain molecular signatures have been identified underlying this tumor, which at times, is either underdiagnosed as a benign vascular tumor, or over diagnosed as a high-grade pleomorphic sarcoma, including a malignant fibrous histiocytoma. Over a 14-year-period, five diagnosed cases of AFH were analyzed. Five tumors occurred in three males and two females, over a wide age-range (median = 21, mean = 30 years); mostly in the extremities (4) (80%). Microscopically, most tumors were circumscribed, comprising large, blood-filed spaces with surrounding histiocytic cells and a "cuff" of lymphoplasmacytic cells. Three tumors revealed solid growth pattern with polygonal to spindle cells, including myxoid matrix in one of these tumors. On molecular analysis, this tumor exhibited EWS-CREB transcript. Immunohistochemically, various tumors were positive for CD68 (n = 2/2), epithelial membrane antigen (n = 3/4), CD99/MIC2 (n = 2/3), and desmin (n = 1/4). All tumors were surgically excised. On follow-up (n = 2), a single patient, who underwent wide-excision was free-of-disease (24 months), while another patient had a recurrence 4 months post tumor excision. This forms as the first documented series on clinicopathological features of AFH, a rare STT, from our country. Significant clinicopathological features include younger age, extremities as commonest site and histopathological appearance of blood-filled spaces with surrounding "cuff" of histiocytic cells and lymphocytes. Tumors with unusual histopathological tumor patterns require molecular confirmation. Surgical resection remains the treatment mainstay.

Histiocytome fibreux angiomatoïde de l’enfant : 6 cas

Angiomatoid fibrous histiocytoma (AFH) is a soft-tissue tumour of uncertain differentiation most often arising in the extremities of children and young adults. AFH is a little-known neoplasm and its rarity may result in it being misdiagnosed as either a reactive lesion or a benign or higher-grade tumour. We report 6 cases of AFH in children and we review the clinicopathological and molecular features of this neoplasm published in the literature. The children (aged 4 to 16 years) presented a single nodule involving the forearm (4/6), the trunk or the buttock, and all 5 nodules appeared spontaneously. Microscopic examination revealed well-circumscribed nodular lesions comprising a fibrous pseudo-capsule, haemorrhagic non-endothelial-lined pseudocystic spaces, and sheets of spindle and ovoid cells with dense surrounding lymphoplasmacytic infiltrate. Tumours were positive for desmin, CD68, CD99 and smooth-muscle actin markers. A fusion gene (EWSR1-ATF1) was found in the 3 cases in which molecular investigation was performed. In our series, a diagnosis of AFH had in no event been evoked after clinical examination and radiological investigation. The diagnosis was based in all cases on recognition of characteristic features during histological examination and it was confirmed in 3 cases by the recognition of fusion genes. Complete excision with wide margins allowed complete cure in all cases, supporting a good prognosis of AFH, although long-term follow-up is still mandatory to rule out relapse or metastases, which although rare, are responsible for fatal cases. To avoid unnecessary surgery in patients with AFH, an ultrasound core-needle biopsy should be performed as a first step in order to provide precise diagnosis enabling complete excision to be performed, with the margins being decided in multidisciplinary meetings involving teams specialised in soft-tissue tumours.

Angiomatoid fibrous histiocytoma: comparison of fluorescence in situ hybridization and reverse transcription polymerase chain reaction as adjunct diagnostic modalities.

Angiomatoid fibrous histiocytoma (AFH) is a rare soft tissue neoplasm of intermediate biologic potential and uncertain differentiation, most often arising in the extremities of children and young adults. Although it has characteristic histologic features of a lymphoid cuff surrounding nodules of ovoid cells with blood-filled cystic cavities, diagnosis is often difficult due to its morphologic heterogeneity and lack of specific immunoprofile. Angiomatoid fibrous histiocytoma is associated with recurrent chromosomal translocations, leading to characteristic EWSR1-CREB1, EWSR1-ATF1, and, rarely, FUS-ATF1 gene fusions; fluorescence in situ hybridization (FISH), detecting EWSR1 or FUS rearrangements, and reverse transcription-polymerase chain reaction (RT-PCR) for EWSR1-CREB1 and EWSR1-ATF1 fusion transcripts have become routine ancillary tools. We present a large comparative series of FISH and RT-PCR for AFH. Seventeen neoplasms (from 16 patients) histologically diagnosed as AFH were assessed for EWSR1 rearrangements or EWSR1-CREB1 and EWSR1-ATF1 fusion transcripts. All 17 were positive for either FISH or RT-PCR or both. Of 16, 14 (87.5%) had detectable EWSR1-CREB1 or EWSR1-ATF1 fusion transcripts by RT-PCR, whereas 13 (76.5%) of 17 had positive EWSR1 rearrangement with FISH. All 13 of 13 non-AFH control neoplasms failed to show EWSR1-CREB1 or EWSR1-ATF1 fusion transcripts, whereas EWSR1 rearrangement was present in 2 of these 13 cases (which were histopathologically myoepithelial neoplasms). This study shows that EWSR1-CREB1 or EWSR1-ATF1 fusions predominate in AFH (supporting previous reports that FUS rearrangement is rare in AFH) and that RT-PCR has a comparable detection rate to FISH for AFH. Importantly, cases of AFH can be missed if RT-PCR is not performed in conjunction with FISH, and RT-PCR has the added advantage of specificity, which is crucial, as EWSR1 rearrangements are present in a variety of neoplasms in the histologic differential diagnosis of AFH, that differ in behavior and treatment.

Solid Form of Angiomatoid Fibrous Histiocytoma: A Diagnostically Challenging Entity

Aim: Angiomatoid fibrous histiocytoma (AFH) is a rare tumor mainly affecting children and young adults. The classic morphology is described as being well encapsulated with a solid cellular proliferation containing histiocyte-like cells, cystic/ hemorrhagic spaces and a surrounding dense lymphocytic infiltrate. Unfortunately, the morphology is not always typical and immunostains are often equivocal. Cytogenetic studies show that many instances of AFH have an EWSR1 gene rearrangement. We describe 8 cases of AFH and review them for lack of any of the characteristic histologic features. Methods and Results: Routine immunohistochemical (IHC) stains as well as FISH studies for EWSR gene rearrangement were preformed on available material. Seven of eight cases lacked at least one major histologic feature and three cases showed a uniformly solid architecture. In addition, three of the seven cases were positive for the EWSR1 gene rearrangement. Conclusion: It is important to recognize the solid form of AFH and not to confuse it with malignancy. FISH studies, when positive, are useful and practical in confirming the diagnosis of AFH in cases with unusual histology.

Endobronchial Pulmonary Angiomatoid Fibrous Histiocytoma

Angiomatoid fibrous histiocytoma (AFH) is a rare soft tissue neoplasm of intermediate biological potential, predominantly occurring in the extremities of children and young adults. It has only recently been reported as a primary lung tumor. We describe 2 cases arising endobronchially harboring EWSR1 gene rearrangements by fluorescence in situ hybridization and, respectively, EWSR1-CREB1 and EWSR1-ATF1 gene fusions by reverse transcription polymerase chain reaction. Histologically, both tumors showed classical features of AFH, comprising multiple nodules of bland spindle to epithelioid cells surrounded by lymphoplasmacytic inflammation and at least a partial fibrous capsule. Both tumors showed focal but strong desmin immunoreactivity, with focal pancytokeratin and epithelial membrane antigen in 1 case. The lung is now a recognized site of AFH occurrence, but tumors arising here can be associated with different gene fusions. It is important to recognize AFH in the pulmonary region, as its behavior at other sites is generally relatively indolent; however, it may be mistaken for metastatic or more aggressive primary lung tumors. It is likely that cases of AFH in the lung may have been previously missed because of their morphologic and genetic overlap with other pulmonary lesions.

Angiomatoid fibrous histiocytoma a series of five cytologic cases with literature review and emphasis on diagnostic pitfalls

Angiomatoid fibrous histiocytoma (AFH) is an uncommon and mostly indolent soft tissue neoplasm, which usually occurs in the subcutaneous tissue of the extremities in children and young adults. Although the histologic features of AFH are well established, reports of its cytomorphology are very limited. This report characterizes the cytomorphologic features of five cases of AFH, with correlation to clinical, histology, and cytogenetic findings. Smears of fine needle aspiration (FNA; four cases) and intraoperative scrape (one case) were reviewed from five patients with a histologically confirmed diagnosis of AFH. A review of six previously reported AFH cases with cytomorphology was also performed. The tumor presented as a cystic, deep dermal mass in three pediatric cases and as a solid, deeply seated mass in two adults. The cytomorphologic features are mostly nondistinctive and include cellular smears with ovoid to spindled histiocytoid cells that may be isolated or in clusters. Some of these cells are atypical and others contain hemosiderin. Large cellular clusters with a capillary structure and a whorled arrangement of tumor cells can be appreciated in some cases. There is always a bloody background, but a lymphoplasmacytic infiltrate is uncommon. The presences of EWSR1 rearrangement in one case and three copies of FUS gene in another case were detected by fluorescence in situ hybridization. Diagnosing AFH by FNA cytology alone can be challenging because of its rarity and usually nonspecific cytologic findings. Clinical correlation and ancillary studies are essential to reach a specific diagnosis of AFH in small needle biopsies.

Angiomatoid Fibrous Histiocytoma

Angiomatoid fibrous histiocytoma (AFH) is a rare soft tissue tumor usually affecting the extremities of children and young adults and has a favorable prognosis. The purpose of this study was to report the magnetic resonance imaging appearance in 2 cases of AFH. Although the overall features of AFH can be confused with other subtypes of malignant fibrous histiocytoma, the young age at presentation, the location of the mass, the presence of intralesional blood-filled cystic spaces with fluid-fluid levels, associated features of hemosiderin deposition, and an enhancing fibrous pseudocapsule are all potential hints favoring this entity.

Imaging characteristics of angiomatoid fibrous histiocytoma of bone

We present the first report of a patient with angiomatoid fibrous histiocytoma of bone in the radiology literature. This tumor initially eluded diagnosis due to its similarities with chronic hematoma and aneurysmal bone cyst. Only two cases of angiomatoid fibrous histiocytoma have been reported in the radiology literature and both of these lesions were in the soft tissues. The fairly distinctive findings in our patient of multiple large cystic chambers with fluid-fluid levels are similar to the findings in the two soft tissue case reports, suggesting that imaging may be used to suggest this specific diagnosis regardless of location, especially in the clinical setting of unexplained hematoma or anemia. Mention of this diagnosis in the radiology report may aid in the final diagnosis at pathology, because special techniques, including fluorescent in situ hybridization, must be applied in order to fully evaluate for the diagnosis.

Utility of FISH in the diagnosis of angiomatoid fibrous histiocytoma: a series of 18 cases

Angiomatoid fibrous histiocytoma is a mesenchymal neoplasm of intermediate malignancy and uncertain histogenesis/line of differentiation, which occurs most commonly in the extremities of children to young adults. It has a characteristic appearance characterized by a proliferation of histiocytoid cells with a lymphoid cuff and fibrous pseudocapsule, simulating the appearance of a neoplasm occurring within a lymph node. However, these classic histological features are not always present. Given the variable appearance of the neoplastic cells and the lack of consistently positive immunohistochemical markers, diagnosis can be problematic. Angiomatoid fibrous histiocytoma has been found to harbor three related translocations, a t(12;16)(q13;p11) resulting in a FUS/ATF1 fusion gene, t(12;22)(q13;q12) resulting in a EWSR1/ATF1 fusion, and t(2;22)(q33;q12) resulting in a EWSR1/CREB1 fusion. Fluorescence in situ hybridization (FISH) probes to EWSR1 and FUS, in theory, should detect all three translocations/gene fusions. We evaluated 18 cases of angiomatoid fibrous histiocytoma for rearrangements of EWSR1 and FUS by FISH, the largest series to date. We found that 13 of 17 (76%) cases of angiomatoid fibrous histiocytoma harbored rearrangements of EWSR1; rearrangements of FUS were not detected in any of the cases. This study affirms that the rearrangement of EWSR1 is a common genetic event in angiomatoid fibrous histiocytoma, and is thus useful diagnostically. This study supports the fact that the rearrangement of FUS is present in only a small minority of angiomatoid fibrous histiocytomas. Interestingly, 24% of the cases were translocation negative, and did not contain rearrangements of EWSR1 or FUS by FISH. Although it is possible that these cases contained cryptic rearrangements of EWSR1 or FUS that were not detectable by our FISH probes, it also raises the possibility that another translocation/gene fusion may be present in angiomatoid fibrous histiocytoma. Finally, we discuss some of the potential pitfalls of this technique, including confusion with other mesenchymal neoplasms containing rearrangement of EWSR1, in particular Ewing's sarcoma/PNET.

Angiomatoid Fibrous Histiocytoma with t(2;22)(q33;q12.2) and EWSR1 Gene Rearrangement

Angiomatoid fibrous histiocytoma (AFH) is a rare soft tissue tumor of low malignant potential. The tumor is mostly seen in the deep dermis and subcutis of the lower extremities in children and young adults. Histologically, the tumor forms lobulated sheets of plump round to spindle cells surrounded by a fibrous pseudocapsule and lymphoid cuff. The cytogenetic and molecular hallmarks of AFH are not well defined. Only 4 of 30 reported cases of AFH have had karyotypic information. We present a case of AFH in the inguinal region of a 12-year-old girl. The tumor showed characteristic histological features, t(2;22)(q33;q12.2), and EWSR gene rearrangement by fluorescence in situ hybridization.

Pleomorphic angiomatoid fibrous histiocytoma: a case confirmed by fluorescence in situ hybridization analysis for EWSR1 rearrangement

Angiomatoid fibrous histiocytoma (AFH) is a neoplasm of uncertain histogenesis with intermediate malignant potential. It occurs in superficial soft tissues in any age group and at any body site, although the typical example occurs on extremities in children/young adults. The neoplasm is usually composed of a bland histiocytoid proliferation of cells with eosinophilic cytoplasm forming a syncytium, often surrounded by a dense fibrous pseudocapsule and lymphoid infiltrate, with abundant intralesional hemorrhage forming blood-filled spaces. AFH may show striking pleomorphism and mitotic activity, and such cases can lead to confusion with other atypical mesenchymal lesions, including pleomorphic sarcomas. Recent findings have shown that a majority of cases of AFH have translocations involving the EWSR1 or FUS genes. We present a diagnostically challenging case of AFH with pleomorphic features and minimal lymphoid and angiomatoid changes involving the superficial subcutis and deep dermis on the scalp of an 8-year-old boy. "Areas with typical AFH morphology were identified and the diagnosis confirmed with identification of an EWSR1..." rearrangement detected by fluorescence in situ hybridization. Pleomorphic AFH should be included in the differential diagnosis of atypical mesenchymal tumors of skin and superficial subcutis and molecular testing may prove helpful in this regard.

Fusion genes in angiomatoid fibrous histiocytoma

Angiomatoid fibrous histiocytoma (AFH) is a rare soft tissue tumor of low malignant potential and uncertain differentiation. Only three genetically investigated cases of AFH have been reported. Two of them displayed a FUS-ATF1 fusion gene and one showed an EWSR1-ATF1 chimera. Using RT-PCR analysis, we have identified the EWSR1-ATF1 fusion transcript, and delineated the genomic breakpoints, in two new cases of AFH. Previously, the EWSR1-ATF1 fusion protein has been suggested to activate expression of the MITF-M transcript, and therefore the expression pattern of the MITF gene was studied. The MITF-M transcript was not detected in either AFH, in line with the finding that the co-activator SOX10 was not expressed. Thus, of the five AFH that have been molecularly analyzed to date, two have displayed a FUS-ATF1 fusion gene and three have shown an EWSR1-ATF1 chimera. There is no apparent correlation between the type of fusion gene and clinicopathologic features. Nonetheless, RT-PCR for these fusion transcripts remains a valuable diagnostic adjunct in the distinction between AFH and other soft tissue tumors or metastases that may simulate it.

The Impact of Genetics on Sarcoma Diagnosis: An Evolving Science

Although current standards for cancer diagnosis and classification are based primarily on histologic characteristics, progress in molecular genetics during the last few decades has enabled the development of new markers beyond the cellular level. Based on these studies, specific genetic changes have

Fusion of theEWSR1andATF1genes without expression of theMITF‐Mtranscript in angiomatoid fibrous histiocytoma

Angiomatoid fibrous histiocytoma (AFH) is a rare soft tissue tumor that usually occurs in children and young adults. Only two cases of AFH with genetic rearrangements have been reported previously; both of these had a FUS-ATF1 fusion gene. We have studied an AFH from a 9-year-old boy whose tumor displayed a t(12;22)(q13;q12) as the sole cytogenetic aberration. FISH,RT-PCR, and sequence analyses revealed an EWSR1-ATF1 fusion gene that has previously been reported in clear cell sarcoma (CCS), a soft tissue sarcoma that is morphologically and clinically distinct from AFH. This study thus has demonstrated that the EWSR1-ATF1 chimera represents a fusion gene that can be associated with different tumor types. Simultaneous expression of the EWSR1-ATF1 and MITF-M transcripts in CCS has led to the proposal that the MITF-M promoter is transactivated by EWSR1-ATF1. The AFH, however, did not express the MITF-M transcript, supporting the theory that MITF-M expression in CCS is a reflection of its cellular origin, rather than a consequence of the presence of an EWSR1-ATF1 fusion protein. Activation of the EWSR1-ATF1 oncogene is probably an early step in the transformation process, but the overall gene expression patterns are likely to vary considerably between AFH and CCS, in keeping with their clinicopathologic differences.

Leiomyosarcoma and malignant fibrous histiocytoma share similar allelic imbalance pattern at 9p

Formalin-fixed, paraffin-embedded tissue from 45 soft tissue sarcomas was analysed for allelic imbalance/loss of heterozygosity (AI/LOH) of chromosome 9. The specimens consisted of 17 cases of soft tissue leiomyosarcoma (LMS), 4 cases of cutaneous LMS, 22 cases of conventional malignant fibrous histiocytoma (MFH) and 2 cases of angiomatoid fibrous histiocytoma. All cases were categorised morphologically and immunohistochemically. DNA was microdissected from normal and neoplastic tissues. AI/LOH was performed using six microsatellite markers on the 9p region. The frequency of allelic imbalance at different loci on chromosome 9p was analysed in LMS and MFH and then compared with values previously examined in synovial sarcoma and malignant peripheral nerve sheath tumour. Although AI/LOH and microsatellite instability (MSI) were more frequent in MFH, LMS and MFH groups showed similar patterns of allelic imbalance at the 9p region. Alterations of chromosome 9p have been reported in many cell lines and tumours including LMS and MFH. 9p21 region encodes p16(INK4A) and p15(INK4B). Allelic imbalance observed at 9p 21 in this study suggests that alterations of the negative cell cycle regulators may be an important step in the pathogenesis of MFH and LMS. However, the most frequent allelic imbalance was observed at 9p24 at D9S230. Alterations of this locus were very rare in synovial sarcoma and malignant peripheral nerve sheath tumours and were absent in cutaneous LMS and angiomatoid fibrous histiocytoma. This locus may point to the existence of a genetically altered tumour suppressor gene involved in the pathogenesis of LMS and MFH. Our results support the hypothesis that MFHs may represent a morphological pathway in tumour progression of LMSs.