A comprehensive review of ossifying fibromyxoid tumor: insights into its clinical, pathological, and molecular landscape

Article information

J Pathol Transl Med. 2026;60(1):6-19

Publication date (electronic) : 2026 January 14

doi : https://doi.org/10.4132/jptm.2025.10.02

Kyriakos Chatzopoulos¹, Antonia Syrnioti¹, Mohamed Yakoub², Konstantinos Linos^,2

¹Department of Pathology, Aristotle University of Thessaloniki, Thessaloniki, Greece

²Department of Pathology and Laboratory Medicine, Memorial Sloan Kettering Cancer Center, New York, NY, USA

Corresponding author: Konstantinos Linos, MD, Department of Pathology and Laboratory Medicine, Memorial Sloan Kettering Cancer Center, 1275 York Avenue, New York, NY 10065, USA Tel: +1-212-639-5905, Fax: +1-212-557-0531, E-mail: linosk@mskcc.org

Received 2025 March 4; Revised 2025 August 4; Accepted 2025 September 24.

Abstract

INTRODUCTION

Ossifying fibromyxoid tumor (OFMT) is a rare soft tissue neoplasm of uncertain histogenesis, typically arising in the soft tissues of the extremities and often in the subcutaneous tissue [1]. First described by Enzinger et al. in 1989 [2], OFMT displays a wide spectrum of morphological findings and biological behavior. While typical histopathological presentations usually pose little diagnostic challenge, the tumor’s morphological variability can complicate diagnosis. This includes cases exhibiting chondroid or lipoblastic differentiation [3], clear cell morphology or collagen entrapment [4], which may mimic other soft tissue neoplasms. Furthermore, hypercellular and mitotically active tumors with significant cellular atypia can demonstrate metastatic potential [5], underscoring the importance of accurate and timely diagnosis. The majority of OFMTs have recurrent molecular alterations, most frequently PHF1 rearrangements [6], and molecular pathology can serve as a valuable adjunct in diagnosing challenging cases [4]. This review aims to provide a comprehensive overview of the clinical, pathological, and molecular characteristics of OFMT, educating the readers on this enigmatic entity.

EPIDEMIOLOGY AND CLINICAL PRESENTATION

Despite the rarity of OFMT, multiple case series have described its clinical and pathologic findings in thorough detail. In most cases, OFMT presents as a long-existing, slow-growing, painless mass, with a median duration of ~4 years before patients seek medical attention and treatment [7]. In the original case series of 59 patients published by Enzinger et al. in 1989 [2], OFMT was diagnosed more frequently in males than females, with age range spanning from 14 to 79 years. In the series of 70 patients published by Folpe and Weiss [5], OFMT was primarily observed in middle-aged adults, with a slight male predominance, and a propensity to arise in the soft tissues of the extremities. These findings were corroborated by a subsequent study of 104 patients from the Armed Forces Institute of Pathology, which highlighted a median age of 50 years at diagnosis, along with a male-to-female-ratio of 1.5:1 [7], as well as the study by Graham et al on 46 patients with a median age of 52 years and male-to-female ratio of 1.7:1 [8]. Apart from the extremities, OFMT frequently arises in various locations of the head and neck region [9-18]. Intracranial involvement [19,20], occasionally with transcranial extension [21], as well as paraspinal [22] or spinal extradural involvement [23] have been described. Other unusual locations include the retroperitoneum [24], the breast [25], and the genitourinary (GU) tract [26]. Pediatric cases, although uncommon, have been reported [27,28], including a 3-week-old male neonate with a left nasal mass [29].

MACROSCOPIC FINDINGS

OFMT typically presents as a well-circumscribed, ovoid, small soft tissue mass, with a rubbery to firm texture, and a glistening, white cut surface. It often features a peripheral hard shell, which can be appreciated on imaging as irregular bone [7,8,30]. Most tumors are small to medium-sized, with a median size of 3–5 cm, although large tumors measuring up to 17 cm or even 21 cm have been reported [5,7,8]. In the appropriate clinico-radiological setting, this finding can occasionally complicate the differential diagnosis with parosteal osteosarcoma [31]. The tumors are most often subcutaneous, although rarely, they may arise within the skeletal muscle, particularly in the head and neck area [7].

MICROSCOPIC FINDINGS

Microscopically, OFMT exhibits a multilobular architecture, with a pressure effect on the superficial component of the overlying skin, occasionally associated with cutaneous ulceration [7]. The tumor is lined by a pseudocapsule with metaplastic lamellar or woven bone, sometimes interspersed with adipocytes between bony trabeculae, but lacking hematopoietic cells. However, it's worth noting that the absence of the peripheral bone shell is reported in ~25%–40% of OFMT [8,32]. Additionally, osteoid material is commonly observed in central regions of the tumor [33], which raises the possibility of osteosarcoma in the differential diagnosis [34]. Pericapsular aggregates of lymphocytes are not uncommon [5,35]. Within a collagenous or myxoid matrix with perivascular hyalinization, the tumor cells are uniform and epithelioid, featuring pale to eosinophilic cytoplasm, round nuclei with even chromatin distribution, delicate nucleoli, inconspicuous clefts or pseudoinclusions, and low mitotic activity [5,7,35] (Fig. 1).

Fig. 1.

A right inferior breast ossifying fibromyxoid tumor displaying nearly classic histologic features (except the peripheral metaplastic bone). This case harbors the classic EP400::PHF1 fusion. (A) At low magnification, the tumor appears as a well-demarcated, multilobulated mass located within the subcutis. (B, C) Tumor cells are arranged in cords and sheets within collagenous stroma. (D) High power view depicting ovoid tumor cells, featuring pale to eosinophilic cytoplasm, and round, regular nuclei.

Unusual findings described in OFMT include breakdown of lamellar bone with osteoclasts, central hemorrhagic infarction [7], satellite microscopic nodules, mucinous microscopic cysts, microcalcification, crushing artifact, and paucity or absence of myxoid matrix, as well as chondroid differentiation (Fig. 2) with atypical binucleated cells [36]. Additional unusual findings are predominance of clear cell morphology, extravasated red blood cells, collagen entrapment and interdigitating fibrocollagenous and fibromyxoid stromal bundles [4] (Figs. 3, 4). A recent study also described two OFMTs with prominent lipoblastic differentiation [3].

Fig. 2.

A lower back ossifying fibromyxoid tumor, harboring a CREBBP::BCORL1 fusion. (A) Low-power view depicting a well-delineated, pseudoencapsulated tumor, featuring prominent central stromal hyalinization. (B, C) Extensive chondroid differentiation and focal clear cell morphology are appreciated. (D) Tumor cells exhibit positivity for S100 on immunohistochemical staining.

Fig. 3.

A left axillary ossifying fibromyxoid tumor harboring an EP400::PHF1 fusion. (A) At low magnification, the tumor is well-defined and distinctly bordered by adjacent adipose tissue. (B) Tumor cells are set within a stromal matrix that transitions between fibrocollagenous and fibromyxoid areas in a geographically interwoven pattern. (C, D) Cords and sheets of spindle-to-ovoid tumor cells with uniform, ovoid nuclei and pale to eosinophilic cytoplasm are noted.

Fig. 4.

The EP400::PHF1 fusion, detected in the case depicted in Fig. 3, preserves SNF2_N from EP400 and fuses to PHF1 exon 2 and the PHD domain, altering chromatin regulation via recruitment to new loci [53]. HAS, actin-binding domain in chromatin remodelers; SNF2_N, ATP-binding subdomain of SNF2 helicase; Helicase_C, catalytic helicase subdomain; PHD, zinc finger "reader" domain binding histone marks; PRC2 interaction, region mediating interaction with the PRC2 complex (Illustrations are created by Biorender https://app.biorender.com).

An OFMT characterized by high nuclear grade or increased cellularity, and mitotic activity exceeding 2 mitoses per 50 high power fields can be classified as malignant [5] (Figs. 5–8). Additionally, necrosis and an infiltrative pattern may be present [8]. Patients with malignant OFMT are more likely to develop distant metastases, most often to the lungs [37]. Although overtly sarcomatous changes in OFMT are uncommon, they have been documented [38], with reported cases including osteosarcoma arising from OFMT after multiple recurrences [39].

Fig. 5.

A malignant, right-back ossifying fibromyxoid tumor harboring an EPC1::SUZ12 fusion. (A) At low magnification, the tumor appears multilobulated and highly cellular. (B, C) Sheets and trabeculae of tumor cells are seen infiltrating the collagen bundles. (D) Areas of increased mitotic activity are observed, with no evidence of pleomorphism or necrosis.

Fig. 6.

EPC1::SUZ12 fusion, detected in the case depicted in Fig. 5, joins the EPcB domain of EPC1 to SUZ12 5′-UTR, reprogramming PRC2 recruitment and function with loss of H3K27 trimethylation [54]. EPcA/EPcB domains, EPC1 domains that scaffold chromatin modifiers; ZnB, Zinc-binding domain (complex assembly function); VEFS, Domain that interacts with EZH2/EED and targets H3K27 (Illustrations are created by Biorender https://app.biorender.com).

Fig. 7.

A malignant right parapharyngeal ossifying fibromyxoid tumor with the very rare PHF1::FOXR2 fusion. (A, B) At low magnification, the tumor appears highly cellular, with metaplastic bone present within the fibrous septae. (C) Tumor cells form cords, nests, and sheets, scattered throughout a collagenous to hyalinized background. (D) The tumor cells are predominantly ovoid to spindle-shaped, with a high nucleus-to-cytoplasm ratio, round to ovoid nuclei featuring occasional small nucleoli, and increased mitotic activity. The patient subsequently developed lung metastases.

Fig. 8.

The PHF1::FOXR2 fusion, detected in the case depicted in Fig. 7, combines PRC2 recruitment ability (PHF1) with the transcriptional targeting domain of FOXR2, redirecting epigenetic silencing to FOX-bound genomic loci and mislocalization of chromatin-modifying complexes [55]. PHD, histone reader domain; FOX (Forkhead domain), DNA-binding domain of FOXR2, found in FOX transcription factors (Illustrations are created by Biorender https://app.biorender.com).

HISTOGENESIS

The histogenesis of OFMT remains enigmatic. Initially it was thought to be a neoplasm of Schwannian origin [40] with possible incomplete neural or cartilaginous differentiation, a hypothesis supported by the commonly observed S100 protein immunoreactivity [7]. However, electron microscopy findings largely resemble those seen in pleomorphic adenomas or myoepithelial tumors [41], including paucity of organelles and aggregates of intermediate filaments with reduplicated basal lamina material [41-43]. Therefore, myoepithelial origin or differentiation is a plausible hypothesis, supported by case reports of tumors displaying intermediate characteristics between OFMT and myoepithelial neoplasms, as discussed below.

CYTOPATHOLOGY

The diagnosis of OFMT on cytology specimens is very challenging, both because of its rarity and the non-specific cytomorphology of the cellular component [44]. However, the presence of a fine fibrillary [45] or myxoid matrix [46], with occasional rosette-like structures [44,45] and particularly osteoid-like material [47] can guide cytopathologists to include OFMT in the differential diagnosis of a soft tissue mass. In addition, the presence of nuclear atypia, including features such as prominent nucleoli, chromatin clumping and irregular nuclear contours, may raise the possibility of malignant OFMT [46].

IMMUNOHISTOCHEMISTRY

OFMT typically expresses S100 protein [7,8] and is frequently positive for excitatory amino acid transporter 4 (EAAT4) [8,38], desmin, neurofilament, CD56 [8], CD10 [7], and insulinoma-associated protein 1 (INSM1) [48]. OFMT often displays mosaic expression of integrase interactor 1 (INI1), due to a commonly present underlying alteration of the SMARCB1 gene, as mentioned in detail below [8,38,49]. Transcription factor E3 (TFE3) nuclear expression is typically seen in OFMT harboring a PHF1::TFE3 fusion [50,51].

Expression of keratins, collagen IV, glial fibrillary acidic protein (GFAP), epithelial membrane antigen (EMA), smooth muscle actin (SMA) [7], CD99 [52], MUC4 (not diffuse) [8] or calponin [56] has occasionally been reported, while OFMT is consistently negative for HMB45, CD34 [7], SOX10 [33], and preferentially expressed antigen in melanoma (PRAME) [57]. Interestingly, estrogen receptor and progesterone receptor (PR) expression has been described in a PHF1-rearranged OFMT of the breast, which also co-expressed STAT6 [25], as well as in a PHF1-rearranged OFMT of the axillary soft tissues [4], while isolated diffuse PR expression was seen in two OFMTs of the extremities with BCOR and TFE3 rearrangements [51].

Of note, expression of pan-tropomyosin receptor kinase (pan-TRK) by immunohistochemistry has been reported in BCOR-rearranged OFMT [58,59]. Given the efficacy of targeted neurotrophic tyrosine receptor kinase (NTRK) inhibition for patients with NTRK-fused tumors [60], this finding is of potential clinical interest. Although the exact mechanism of pan-TRK expression has not been fully elucidated, it seems that it occurs due to underlying NTRK3 mRNA overexpression [58].

Finally, it is worth mentioning that malignant OFMT can show an atypical immunophenotype, with attenuation or complete absence of S100 protein expression [61]. Absence of S100 expression was also demonstrated in all four GU OFMTs described by Argani et al. [26], two of which were classified as malignant based on mitotic count.

MOLECULAR GENETICS

The presence of clonal chromosomal alterations such as aneusomies, unbalanced translocations [62] and complex karyotypes [63], including marker chromosomes [64], was highlighted in early studies. Complex karyotypes have been particularly associated with malignant OFMT cases exhibiting metastases [63]. A relatively recurrent finding is hemizygous deletion of chromosome 22 or 22q, leading to hemizygous loss of SMARCB1, an alteration corresponding to the mosaic immunohistochemical pattern of INI1 expression frequently observed, as mentioned above [8]. Another recurrent finding most often seen in atypical and malignant OFMT is loss of the RB1 tumor suppressor gene, observed in almost a third of cases [55].

The molecular hallmark of OFMT is the presence of recurrent rearrangements of PHF1, which are seen in approximately 80%–85% of tumors [6]. The PHF1 gene encodes a protein which interacts with polycomb-repressive complex 2 (PRC2), an important regulator of chromatin structure and developmental gene expression [65], ultimately controlling histone H3K27 methylation status [66]. Rearrangement of PHF1 typically occurs in the form of a reciprocal translocation, resulting in gene fusion, with EP400 being the most common fusion partner (Fig. 4) [67]. Other PHF1 fusion partners include EPC1, MEAF6 [68], TFE3 [69], FOXR1, FOXR2 (Fig. 8) [70], CREBZF [34], TP53 [71], and JAZF1 [3].

Non-PHF1 fusions have also been described, including MEAF6::SUZ12 [72], EPC1::SUZ12 (Fig. 6) [4], CREBBP::BCORL1, KDM2A::WWTR1 [73], ZC3H7B::BCOR [59], CSMD1::MEAF6 [55], and EPC1::PHC1 [3]. The common denominator of these fusions is that they function as tumor drivers, inducing significant epigenetic changes via histone modification, a process currently regarded as the major molecular mechanism of OFMT pathogenesis [55]. Of note, a non-fused malignant OFMT with a BCOR internal tandem duplication has been reported in a pediatric patient with a lateral neck mass and subsequent local and metastatic recurrences [74].

Interestingly, certain of the above mentioned fusions, particularly JAZF1::PHF1, EPC1::PHF1, MEAF6::PHF1, ZC3H7::BCOR, and EPC1::SUZ12 [75,76] have been previously described in low-grade endometrial stromal sarcoma (ESS), a finding explaining why certain OFMT may cluster with ESSs by DNA methylation analysis [4]. The latter fact may limit the utility of DNA methylation assay in the work-up of OFMT.

Given the frequency of PHF1 rearrangements, a reasonable approach includes morphological assessment with confirmation of PHF1 alteration by break-apart fluorescent in situ hybridization (FISH) [77]. However, in cases with unusual morphological findings and non-PHF1 rearrangements, the final diagnosis may need to be deferred until molecular testing by next generation sequencing (NGS) is performed [4].

DIFFERENTIAL DIAGNOSIS

The broad spectrum of the differential diagnosis for OFMT often encompasses myoepithelial neoplasms [78]. In challenging cases, testing for EWSR1 rearrangements in these neoplasms can provide valuable insights. However, it's essential to acknowledge that EWSR1 rearrangements are detected in only around 50% of soft tissue myoepithelial neoplasms [79], making the test informative when positive, but less conclusive when negative.

The most frequent pitfall in the differential diagnosis of OFMT is low-grade fibromyxoid sarcoma (LGFMS) [80]. Also known as “Evans tumor” [81], LGFMS is a low-grade sarcoma arising in the extremities of young adults, although as many as 20% of cases occur in patients younger than 18 years old. It consists of spindle to epithelioid cells arranged in alternating hyalinized and myxoid areas, with occasional hyaline rosettes [82]. These morphologic features, along with lack of S100 expression and strong and diffuse MUC4 positivity, usually suffice for distinguishing LGFMS from OFMT. Molecular detection of the characteristic FUS::CREB3L2 or EWSR1::CREB3L1 fusions confirms the diagnosis of LGFMS in the appropriate morphologic context [83].

Sclerosing epithelioid fibrosarcoma (SEF) or hybrid SEF-LGFMS tumors are also frequently included in the differential diagnosis. SEF is a rare aggressive variant of fibrosarcoma, characterized by small epithelioid cells arranged in cords and nests within a densely sclerotic stroma [84]. However, unlike OFMT, SEF primarily arises in deep soft tissues and lacks S100 expression [85]. The diagnosis of SEF can be confirmed through molecular studies that identify the characteristic EWSR1::CREB3L1 fusion [86].

The differential diagnosis also includes the newly described YAP1::KMTA2-rearranged sarcoma, an aggressive soft tissue malignancy, notorious for its propensity to mimic benign or low-grade neoplasms, such as schwannoma, fibromatosis or LGFMS [87]. Initially thought to represent a MUC4-negative subtype of SEF, the identification of recurrent YAP1 and KMT2A rearrangements [88,89], along with distinctive morphologic features [89] and a unique DNA methylation profile [87], has established YAP1::KMT2A rearranged sarcoma as a novel entity. These tumors usually exhibit an infiltrative growth pattern with areas of variable cellularity, where monomorphic epithelioid or bland, fibroma-like spindle cells are embedded in a densely collagenous matrix. Mitotic activity is generally low and high-grade features, such as necrosis are usually absent [89]. Immunohistochemically, these tumors are consistently negative for MUC4 and usually negative for S100 protein, but may show variable EMA or CD34 expression [86]. Despite its deceptively low-grade histomorphology, YAP1::KMT2A-rearranged sarcoma can follow an aggressive clinical course, with local recurrence and metastatic disease developing in up to 50% of patients [86].

Other entities to consider in the differential diagnosis include schwannoma [90], malignant peripheral nerve sheath tumor (MPNST) [78], extraskeletal myxoid chondrosarcoma (EMC) [48], and extraskeletal osteosarcoma [78]. Schwannoma arises from the peripheral nerve sheath and is characteristically strongly and diffusely positive for S100 protein, in contrast to OFMT, where S100 expression may be weak or absent. Schwannomas also lack the peripheral ossification and cytomorphologic features typical of OFMT [90]. MPNST typically arises in deep soft tissues, often in association with major nerves, and does not exhibit peripheral ossification. While MPNST may show attenuated S100 positivity, it can also express other neural markers such as neurofilament and GFAP [78]. Importantly, loss of H3K27me3 expression—frequently seen in MPNST—can help distinguish it from OFMT, in which H3K27me3 expression is consistently retained [91,92]. EMC is characterized by a lobular architecture with fibrous septa and uniform tumor cells showing eosinophilic cytoplasm, occasional spindling, and inconspicuous nucleoli in a myxoid background. EMC typically expresses INSM1, synaptophysin, and sometimes other neuroendocrine or neural markers such as chromogranin, PGP9.5, microtubule-associated protein 2, class III β-tubulin, and peripherin [48]. Genetically, EMC is defined by NR4A3 rearrangements, most commonly with EWSR1, but also involving partners such as TAF15, TCF12, TFG, FUS, HSPA8, LSM14A, or SMARCA2 [48]. Extraskeletal osteosarcoma is exceedingly rare in the skin or subcutis and typically represents metastatic disease, making clinical history essential. Helpful distinguishing features include lack of S100 expression and the presence of marked nuclear atypia [78].

Notably, primary bone OFMT has also been described, which may be extremely challenging to distinguish from osteosarcoma [93]. In tumors with lipoblastic differentiation, distinction from benign and malignant lipomatous tumors such as chondroid lipoma or myxoid liposarcoma can be challenging [3]. The differential diagnosis can be particularly challenging in tumors with uncommon microscopic features, where the final diagnosis can be confidently rendered only by confirming a characteristic molecular alteration [4].

PRACTICAL DIAGNOSTIC APPROACH

Diagnosing OFMT requires an integrative approach, as the tumor's morphologic and immunophenotypic spectrum is broad and overlaps with several benign and malignant entities. In classic presentations—characterized by uniform ovoid cells embedded in a fibromyxoid matrix and surrounded by a peripheral shell of metaplastic bone—the diagnosis may be straightforward, particularly when supported by strong S100 protein and desmin expression. However, in atypical or malignant variants, these features may be attenuated or absent. For instance, malignant OFMTs frequently lack ossification, exhibit increased cellularity and mitotic activity, and may show reduced or completely lost S100 expression. Ancillary studies are essential in such cases. FISH is widely used and can detect gene rearrangements or amplifications in formalin-fixed paraffin-embedded tissue with good sensitivity, but it is restricted to one locus per assay and, in the case of break-apart probes, cannot identify the fusion partner. Furthermore, cryptic or complex rearrangements may go undetected. Reverse-transcriptase polymerase chain reaction (RT-PCR) offers high sensitivity and relatively low cost for detecting known fusion transcripts, but it requires prior knowledge of the partner genes and thus cannot identify novel fusions. Targeted RNA sequencing and broader NGS panels overcome these limitations by interrogating multiple loci simultaneously, allowing both confirmation of established fusions and discovery of novel ones. Although more resource-intensive, NGS has emerged as the most reliable method for characterizing OFMT at the molecular level, particularly in diagnostically challenging cases [94].

In clinical practice, the diagnostic work-up of a suspected OFMT typically begins with a panel of broad immunohistochemical stains, including S100, SOX10, desmin, SMA, and a broad-spectrum cytokeratin. In tumors with classic morphology, the combination of S100 and desmin positivity is generally sufficient to establish a confident diagnosis. In cases with very suggestive morphology but incomplete immunophenotypic support—for example, when S100 or desmin expression is weak or focal—PHF1 break-apart FISH is the logical next step, as approximately 80%–85% of OFMTs harbor PHF1 rearrangements. If PHF1 testing is negative but the pretest probability remains high, RT-PCR, targeted RNA sequencing or broad-panel NGS can help identify rarer fusions, such as CREBBP::BCORL1, EPC1::SUZ12, or ZC3H7B::BCOR amongst others.

In atypical or malignant cases, where classic immunohistochemical markers such as S100 and desmin are diminished or absent, a diagnosis of OFMT may still be appropriate if the tumor contains areas reminiscent of conventional OFMT. In such instances, PHF1 FISH remains useful. However, in malignant tumors that lack both morphologic and immunophenotypic features suggestive of OFMT, comprehensive molecular testing via NGS is often the only practical means of confirming the diagnosis.

Emerging evidence supports a correlation between specific gene fusions and atypical or malignant histologic features of OFMT. In a synthesis of reported cases across the literature, approximately 26 OFMTs with non-PHF1 fusions or PHF1 fusions involving uncommon partners (e.g., TP53, FOXR1/2, CREBZF, ZC3H7B, EPC1) have been compiled and analyzed. Of these, 18 tumors (69%) were classified as atypical or malignant, indicating a strong association between rare fusion events and aggressive histologic behavior. Moreover, certain fusion types—such as TP53::PHF1, PHF1::FOXR2, ZC3H7B::BCOR, and EPC1::SUZ12—have been reported almost exclusively in malignant cases, further supporting their potential as molecular indicators of high-grade disease. While these rare fusions do not inherently define malignancy, their frequent occurrence in morphologically aggressive tumors suggests they may play a role in driving dedifferentiation or loss of canonical OFMT features.

These atypical/malignant variants also tend to show marked loss of conventional immunophenotypic markers. In the pooled dataset, S100 expression was retained in only four of 15 cases (27%), often in a focal or patchy distribution, and desmin was expressed in just two of 14 cases (14%). In contrast, classic OFMTs show S100 positivity in ~70% and desmin in ~50% of cases. Additionally, the characteristic peripheral ossified shell was frequently absent in these high-grade tumors, further complicating diagnosis.

Together, these findings highlight the importance of recognizing non-classic morphologic and immunohistochemical presentations and maintaining a low threshold for molecular testing—especially in tumors lacking both classic architecture and marker expression [71].

TREATMENT AND PROGNOSIS

OFMT is treated surgically with local marginal or wide excision and rarely amputation, particularly when a large tumor arises on a digit [7]. Local recurrence is more likely to occur in patients whose tumors show increased mitotic activity [7]. Tumors fulfilling the microscopic criteria of malignancy, should be regarded as sarcomas for treatment purposes, as they tend to display more aggressive clinical behavior, including the potential for distant metastasis [5,95]. These patients may be candidates for adjuvant radiation therapy, particularly after being diagnosed with local recurrence [5]. Similarly, patients with metastatic disease may be eligible for chemotherapy [96]. When malignant OFMT metastasizes, it typically spreads to the lung [8,37,96], although unusual locations such as the thyroid gland have been reported [97].

CONCLUSION

OFMT is a rare mesenchymal neoplasm that can occasionally complicate the differential diagnosis of a soft tissue mass, leading to diagnostic uncertainty. Given that certain tumors behave in a clinically aggressive manner, pathologists should consider OFMT in the differential diagnosis of an unusual soft tissue tumor and triage cases for molecular testing where appropriate, as rendering an accurate diagnosis is the cornerstone of effective patient management.

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