Ossifying Fibromyxoid Tumor: Modified Myoepithelial Cell Tumor? Report of Three Cases with Immunohistochemical and Electron Microscopic Studies

Round cell tumor with a myxoid matrix harboring a PHF1-TFE3 fusion: Myoepithelial neoplasm or ossifying fibromyxoid tumor?

Myoepithelial tumors arising in soft tissue are uncommon and mostly manifest a benign clinical course, although a malignant form does exist. An EWSR1 gene rearrangement is a common event in these tumors. Ossifying fibromyxoid tumor, a rare soft tissue neoplasm of uncertain differentiation, may have overlapping histologic and immunophenotypic features with myoepithelial tumors, but frequently harbors a PHF1 gene rearrangement. Interestingly, a PHF1-TFE3 fusion has been recently reported in both entities. Here we report a case of a malignant soft tissue tumor demonstrating myoepithelial differentiation and harboring a PHF1-TFE3 fusion. Despite being slow-growing and lacking significant cytologic atypia at initial presentation, the patient deteriorated rapidly with local recurrence and distant metastases. A discussion of the potential clinicopathologic implications of a PHF1-TFE3 fusion in these entities is also developed.

Ossifying Fibromyxoid Tumor: A Review With Emphasis on Recent Molecular Advances and Differential Diagnosis

CONTEXT.—

Ossifying fibromyxoid tumor (OFMT) is a rare, slow-growing mesenchymal neoplasm of uncertain histogenesis with intermediate malignant potential.

OBJECTIVE.—

To highlight the most important diagnostic features, including morphologic, immunohistochemical, and molecular findings; to provide comparisons to other entities in the differential diagnosis; and to provide a summary of the clinical features and outcomes in cases reported to date.

DATA SOURCES.—

The data sources include recently published literature encompassing OFMT and tumors in the histologic differential diagnosis, and cases from institutional files.

CONCLUSIONS.—

Ossifying fibromyxoid tumor is important to recognize because of its low-grade morphology but potential for recurrence and metastasis. Recent molecular analysis has expanded the morphologic spectrum of OFMT, with additional cases discovered that are enriched for aggressive behavior. The diagnosis can often be rendered through a combination of morphology and coexpression of S100 protein and desmin, although only a minority of cases described contain all of these primary features. In cases that do not have all of these features, a high index of suspicion guided by morphology and exclusion of other tumors in the histologic differential diagnosis can lead to the correct diagnosis. Growing access to molecular genetic testing will become increasingly important for correct diagnosis of tumors at the ends of the morphologic spectrum.

Ossifying fibromyxoid tumor: Fine-needle aspiration cytology findings of a rare soft tissue neoplasm

Ossifying fibromyxoid tumors (OFMTs) are rare tumors of uncertain origin and intermediate (rarely metastasizing) biologic potential, with characteristic morphology of an encapsulated tumor containing polygonal cells in an abundant fibromyxoid matrix surrounded by a peripheral layer of metaplastic lamellar bone. FNA cytology of OFMT has not been sufficiently reported and till date cytological features of only seven cases have been reported so far. We report another case of OFMT in a 55-year-old female presenting with longstanding swelling in thigh. On fine-needle aspiration, a tumor with moderate cellularity and myxoid areas was seen; coupled with compatible radiological findings, a diagnosis of OFMT was suggested. Establishing a correct diagnosis is important as although OFMT is benign in nature, local recurrences or rarely distant metastasis have been seen of this tumor. Hence, a high degree of suspicion with radiological correlation is of utmost importance for identification of this entity.

Soft Tissue Tumors of Uncertain Histogenesis: A Review for Dermatopathologists

The mesenchymal tumors discussed herein represent a heterogeneous group of neoplasms with distinctive morphologic, immunophenotypic, and molecular genetic features. These uncommon tumors often arise in the dermis and subcutis and can pose a major diagnostic challenge to dermatopathologists because they closely mimic melanoma, carcinoma, fibrous histiocytoma, schwannoma, or granulomatous inflammation. This article reviews the clinical presentation, histopathology, differential diagnosis, and diagnostic pitfalls of epithelioid sarcoma, clear cell sarcoma, perivascular epithelioid cell tumor, ossifying fibromyxoid tumor, pleomorphic hyalinizing angiectatic tumor, and hemosiderotic fibrolipomatous tumor. Associated molecular genetic findings are also briefly reviewed with an emphasis on their diagnostic usefulness.

Ossifying Fibromyxoid Tumor May Express CD56 and CD99: A Case Report

Ossifying fibromyxoid tumor (OFMT) is an uncommon soft tissue neoplasm characterized by a combination of myxoid and/or fibrous stroma with areas of ossification. Although most authors postulate a neuroectodermal origin for this peculiar tumor, there is no agreement in the literature regarding its histogenesis. In this article, we present the immunohistochemical findings of a case of a 39-year-old white male with an OFMT of the soft tissue in the mandibular region. The tumor was positive to S-100 protein, glial fibrillary acidic protein, CD99, CD56 and negative to smooth muscle actin, cytokeratins AE1/AE3, epithelial membrane antigen, and CD68. To the best of our knowledge, this is the first case reported to be positive to CD56 and CD99. Immunoreactivity to these two antibodies, together with reactivity for S-100 protein and glial fibrillary acidic protein, suggests that OFMT is of a neuroectodermal origin. In our opinion, in the absence of reactivity to at least one neuroectodermal marker one should seriously question a diagnosis of OFMT.

Ossifying Fibromyxoid Tumor: An Update

Ossifying fibromyxoid tumor (OFMT) is a rare soft tissue neoplasm of uncertain differentiation, initially described by Enzinger and colleagues. Until now, nearly 300 such cases have been reported worldwide. The histogenesis of these tumors remains controversial. These tumors show characteristic imaging findings and exhibit a spectrum of histopathologic features, including classical and atypical subtypes. Local recurrences and, occasionally, distant metastases have also been reported. A complete tumor resection forms the preferred treatment modality for these tumors, along with follow-up, as these tumors have an uncertain malignant potential. Lately, certain “molecular signatures” underlying OFMTs have been described that can further aid in reaching an accurate diagnosis for these tumors and unraveling their pathogenesis. This article is a review of the clinical, radiologic, histopathologic, and molecular features of OFMTs.

Ossifying fibromyxoid tumor: a clinicopathologic analysis of 26 subcutaneous tumors with emphasis on differential diagnosis and prognostic factors

INTRODUCTION

Ossifying fibromyxoid tumor (OFMT) is rare and may present diagnostic difficulty. We describe 26 subcutaneous examples of OFMT emphasizing differential diagnosis and prognostic features.

METHODS

Histopathology and follow-up data from archival/consultation cases were reviewed. Prognostic features were assessed according to proposed criteria.

RESULTS

Patients (16 female, 10 male) ranged from 26 to 88 years (median 54). The tumors (median 2.3 cm, range 0.8-8.5) involved lower limb (11), trunk (7), head/neck (4), or arm (4). All showed combinations of corded, nested and trabecular patterns in a fibromyxoid stroma. Out of 26 cases 13 had peripheral ossification. Sixteen of 22 cases showed S100 protein expression. Nuclear grade was low (14); intermediate (8) and high (4) while cellularity was low (14); moderate (7) and high (5), with overall good interobserver agreement. Median mitotic rate was 3/50HPF (0-61). Five met criteria for malignant OFMT showing high nuclear grade or high cellularity and mitotic rate >2/50HPF or both. Thirteen OFMTs were atypical. Follow-up (16/26, median 45.5 months, range 8-108) showed that patients with typical OFMT (3) and atypical OFMT (9) remained disease-free. Three malignant examples of OFMT recurred and one metastasized to the lung. No deaths were recorded.

CONCLUSIONS

Our results validate proposed prognostic classification of OFMT. Dermatopathologists should be aware of this unusual superficial tumor given its potentially aggressive behavior.

Primary pulmonary myxoid sarcomas with EWSR1-CREB1 translocation might originate from primitive peribronchial mesenchymal cells undergoing (myo)fibroblastic differentiation

Primary pulmonary myxoid sarcoma (PPMS) is a very rare lung tumor that has recently been shown to harbor an EWSR1-CREB1 translocation. However, the histogenesis and biological behavior of PPMS remains unclear. To provide insight into the histogenesis of PPMS, we studied surgical resection specimens of four patients, two females and two males with an age range of 26 to 65 years, all non-smokers with mild anemia. The tumors, three of which are endobronchial, measured between 4 and 13 cm. One patient developed metastasis to the contra-lateral lung 7 months after resection. Other patients remained alive without tumor for 1.5, 10, and 13 years. Fluorescence in situ hybridization (FISH) analysis with a gene break apart probe showed an EWSR1 translocation in all cases. The EWSR1-CREB1 fusion transcript was detected in all cases by reverse-transcription PCR. Immunohistochemical staining showed diffuse positive staining of the tumor cells only for vimentin. Tumor cells expressed no other myoid, epithelial, endothelial, melanocytic, myoepithelial, or neuroendocrine markers, except for smooth muscle actin and epithelial membrane antigen, which were only focally positive in individual cases. Ultrastructural analyses revealed the presence in the tumor cells of intermediate filaments with focal densities along the sub-cytoplasmic membrane as well as dense plaques. These results suggest that PPMS exhibits myofibroblastic differentiation. We conclude that PPMS is an intermediate grade malignant lung tumor harboring EWSR1 translocations, which may originate from mesenchymal cells that undergo fibroblastic or myofibroblastic differentiation.

Ossifying fibromyxoid tumor of soft parts: a clinicopathologic, proteomic, and genomic study

Ossifying fibromyxoid tumor (OFMTs) of soft parts is a rare soft tissue and bone tumor of borderline malignancy displaying an uncertain line of differentiation. The existence of fully malignant OFMT is controversial. To better understand the natural history and line of differentiation taken by OFMT, we studied 46 cases by light microscopic, immunohistochemical (IHC), genomic, proteomic, and fluorescence in situ hybridization (FISH) methods. Cases were classified according to the 2003 Folpe and Weiss system. Clinical and follow-up information was obtained. IHC for S-100 protein, desmin, epithelial membrane antigen (EMA), cytokeratins, smooth muscle actin (SMA), INI-1, neurofilament protein (NFP), CD56d excitatory amino acid transporter-4 (EAAT4), and MUC4 was performed on formalin-fixed, paraffin-embedded (FFPE) tissues. Gene expression profiling and proteomic studies were conducted on FFPE tissues from 13 and 5 cases, respectively. FISH for INI-1 was performed on 10 cases. The 46 tumors arose in 29 men and 17 women (median age, 52 y; range 39 to 63 y) and involved the proximal (N=17) and distal extremities (N=13), head and neck (N=9), and trunk (N=5). Median tumor size was 5.4 cm (range, 1.0 to 21.0 cm). Cases were classified as typical OFMT (26 of 46, 57%), atypical OFMT (5 of 46, 11%), and malignant OFMT (15 of 46 cases, 32%). Clinical follow-up (27 cases, median 55 months' duration) showed all patients with typical and atypical OFMT to be alive without disease. Adverse events, including 3 local recurrences, 3 metastases, and 3 deaths, were seen only in malignant OFMT. IHC results were as follows: S-100 protein (30 of 41, 73%), desmin (15 of 39, 38%), cytokeratin (4 of 35, 11%), EMA (5 of 32, 16%), SMA (2 of 34, 6%), INI-1 (lost in mosaic pattern in 14 of 19, 74%), EAAT4 (31 of 39, 80%), MUC4 (3 of 14, 21%), NFP (8 of 10, 80%) and CD56 (6 of 14, 43%). Gene expression profiling showed typical and malignant OFMTs to cluster together, distinct from schwannian tumors. Proteomic study showed expression of various collagens, S-100 protein, and neuron-related proteins. FISH showed INI-1 deletion in 5 of 7 (71%) cases. We conclude that malignant OFMTs exist and may be recognized by the previously proposed criteria of Folpe and Weiss. Expression of neuron-related markers, in addition to Schwann cell and cartilage-associated markers, suggests a "scrambled" phenotype in OFMTs. Loss of INI-1 or other genes on 22q is likely important in the pathogenesis of these rare tumors.

Ossifying fibromyxoid tumour: a rare soft tissue tumour of intermediate malignancy

Ossifying fibromyxoid tumours (OFTs) are uncommon soft tissue tumours. A 73-year-old male presented with a painless exophytic mass located in the left scapular area which was identified 1 year earlier. An incisional biopsy was performed and microscopic features were compatible with OFT. Radiologic evaluation revealed multiple pulmonary metastasis. Although many cases persue an indolent biologic behaviour, local recurrence and metastasis have been reported and long-term follow-up should be considered.

Paraspinal malignant ossifying fibromyxoid tumor with spinal involvement

Ossifying fibromyxoid tumors (OFT), first described in 1989 by Enzinger et al., are rare lesions; malignant OFT (MOFT) are even rarer. We report a large recurrent paraspinal MOFT invading the spine and causing epidural compression in a 70-year-old male, despite prior debulking and radiotherapy. Paraspinal involvement of these tumors has been reported only twice before. We describe its imaging, pathology, and also review the pertinent literature.

Ossifying fibromyxoid tumor invading the spine: a case report and review of the literature

Ossifying fibromyxoid tumors were first described in 1989. They are composed of small round cells dispersed in a myxoid matrix and contain bone, osteoid, and collagen. Bone invasion is very rare. Our case was unusual because of the spinal location of the tumor and its invasive features including destruction of the cortex of the vertebral body, and invasion of the spinal canal causing a radioculopathy. The clinical presentation, radiologic features, and histopathologic findings are described, and the relevant literature is reviewed.