Smooth muscle actin (SMA)-negative uninodular plexiform fibromyxoma: case report of a challenging atypical presentation of a rare gastric mesenchymal tumor in a 25-year-old female

Introduction

Plexiform fibromyxoma (PFM) is a rare, benign mesenchymal neoplasm of the gastrointestinal tract, historically described under various terms such as fibromyxoma, myxoma, or more recently as plexiform angiomyxoid myofibroblastic tumor (1,2). Since its initial characterization in 2007 (2), several case series have expanded the clinicopathologic understanding of PFM. However, fewer than 200 cases have been reported in the literature to date (3,4). Patients are typically diagnosed between 7 and 75 years of age, with a median age of 41–51 years, and both sexes are affected equally (1,3). The tumor predominantly arises in the gastric antrum (1,3), particularly in the pyloric region, although rare cases involving other gastric regions, the esophagus, intestine, and gallbladder have also been described (5-11). Clinical symptoms are often nonspecific and may include ulceration, abdominal distension, gastrointestinal bleeding, and anemia (1). In some instances, PFM is detected incidentally during imaging or endoscopic procedures (3). Histologically, PFM is characterized by bland tumor cells with ovoid to spindle-shaped nuclei and lightly eosinophilic cytoplasm arranged in a multinodular, plexiform architecture, embedded within a fibromyxoid stroma with a prominent arborizing capillary network (1,3,12). The tumor frequently exhibits an infiltrative margin toward the mucosa or muscularis propria (1). However, rare variants limited to the mucosa/submucosa have been reported (13). Features such as cellular atypia, increased mitotic activity, or necrosis are generally absent (3). The typical immunophenotype includes strong positivity for smooth muscle actin (SMA) and vimentin, and negativity for CD117 (KIT), DOG1, CD34, desmin, S100, and anaplastic lymphoma kinase (ALK). This profile aids in distinguishing PFM from histologic mimickers such as myxoid variants of gastrointestinal stromal tumors (GISTs), inflammatory fibroid polyps (IFPs), myxoid leiomyomas, plexiform neurofibromas, schwannomas, and inflammatory myofibroblastic tumors (IMTs) (1). In contrast to PFM, GISTs demonstrate strong expression of DOG1 and CD117, and frequently harbor activating mutations in KIT or platelet-derived growth factor receptor alpha (PDGFRA), typically involving exons 11 and 9 for KIT and exon 18 for PDGFRA (1). Moreover, a prominently myxoid stroma is rare among GISTs and occurs more frequently in the epithelioid PDGFRA-mutated subtype (14). GISTs generally form solitary, well-demarcated masses and lack the distinctive plexiform intramural growth pattern of PFM (1,14). The pathogenesis of PFM remains incompletely understood, but differs clearly from that of GIST, given the absence of canonical KIT or PDGFRA mutations (3). In a subset of cases, alterations involving the GLI1 gene have been reported, indicating activation of the Hedgehog signaling pathway, which plays an important role in gastrointestinal tract development (3,15-17).

IFPs, another important differential diagnosis, are characterized by CD34 positivity and a perivascular, concentrically layered onion-skin growth pattern (18). These lesions frequently exhibit PDGFRA mutations, most often in exon 12 (19,20). In contrast, PFM lacks CD34 expression and PDGFRA mutations. Myxoid leiomyomas may exhibit tortuous, plexiform growth and SMA positivity (1,21); however, they are typically well-circumscribed and composed of fascicles of tumor cells closely resembling normal smooth muscle, with uniform, blunt-ended nuclei and dense eosinophilic cytoplasm. These tumors also express additional smooth muscle markers such as desmin and h-caldesmon (21). Plexiform neurofibromas and schwannomas, both of neural origin, are typically distinguishable by their characteristic histomorphology and consistently strong, diffuse expression of S100 and SOX10. IMTs may express ALK in a subset of cases, especially in younger patients, and often harbor ALK gene rearrangements. They typically co-express SMA and desmin (22).

Beyond this core immunoprofile, additional markers may assist in the evaluation of diagnostically challenging mesenchymal gastric tumors. Nuclear expression of STAT6 is a highly sensitive and specific indicator of solitary fibrous tumor (SFT), reflecting the underlying NAB2-STAT6 gene fusion, whereas non-SFT mesenchymal neoplasms generally lack strong nuclear STAT6 staining (23-25). Loss of SDHB expression identifies SDH-deficient GIST, a subset of KIT/PDGFRA-wild-type gastric GISTs that typically occur in children and young adults and show limited response to standard tyrosine kinase inhibitor therapy (26,27). Desmoid-type fibromatosis, in contrast, is strongly associated with activating CTNNB1 mutations and aberrant nuclear accumulation of β-catenin, which serves as a useful immunohistochemical marker (28).

Nevertheless, the histological and immunophenotypic features of PFM are not always consistent. Rare cases, such as the one presented here, an uninodular architecture with SMA negativity, show atypical features, complicating the diagnostic process.

Thus, a complete diagnostic approach integrating histopathology, immunohistochemistry, and molecular testing is essential for accurate diagnosis and appropriate clinical management. We present this article in accordance with the CARE reporting checklist (available at https://acr.amegroups.com/article/view/10.21037/acr-2025-295/rc).

Case presentation

A 25-year-old female initially presented to an emergency department with diffuse mid-abdominal pain and progressive abdominal distension. Also, she noted a newly palpable epigastric mass during self-examination. Routine laboratory tests were unremarkable, and there was no evidence of anemia or systemic inflammation. Subsequent esophagogastroduodenoscopy showed no intraluminal abnormalities. The patient was then referred to the Charité-Universitätsmedizin Berlin, a tertiary care center, for further evaluation. On clinical evaluation in our outpatient clinic, we saw a very slim young woman with a firm, sharply demarcated lesion palpable through the abdominal wall, without tenderness or signs of peritonism, and with otherwise normal vital parameters and general condition. There was no history of prior abdominal surgery, no regular medication, no known personal or family history of malignancy or hereditary tumor syndromes, and the psychosocial history was unremarkable.

Abdominal ultrasonography and contrast-enhanced computed tomography (CT) revealed a well-circumscribed, non-homogeneous mass measuring 13 cm in greatest dimension, arising from the antral region of the gastric wall (Figure 1). The lesion exhibited smooth, regular borders without radiological evidence of local infiltration, suspicious for, but not completely typical of, a GIST. Dynamic contrast administration showed a gradually heterogeneous enhancement pattern, and the absence of significant diffusion restriction on magnetic resonance imaging (MRI) further suggested a benign-appearing, though indeterminate, mesenchymal lesion. As the initial punch-biopsy could not clarify the entity of the lesion, surgical resection was recommended by our interdisciplinary tumor conference for sarcomas. Preoperative laboratory work-up, including complete blood count, basic biochemistry, and coagulation studies, was unremarkable (Table 1).

Figure 1 Appearance in diagnostic imaging. Pre-operative computed tomography scan showing tumor with non-homogenous tissue and an indicative connection to the gastric antrum.

A solitary, solid tumor adjacent to the gastric antrum, with no invasion of other tissues or evidence of peritoneal dissemination was identified laparoscopically. The tumor was then resected en bloc via mini-laparotomy with a scarce tangential gastric resection using a stapling device. Frozen section showed negative resection margins, and the integrity of the gastric wall was preserved. This limited, tangential gastric resection was selected to achieve complete tumor removal with negative margins while maintaining gastric function, based on the intraoperative impression of a benign, well-demarcated lesion.

The postoperative course was uneventful. No intra-abdominal drains were placed. On postoperative day 1, the patient experienced mild postoperative nausea and vomiting, but oral intake could be advanced without complications thereafter. She was discharged home in good general condition on postoperative day 3.

Macroscopic examination of the resected specimen revealed a well-demarcated, yellowish, myxoid tumor (Figure 2). Although the lesion was anatomically adjacent to the stomach, histological assessment confirmed that the gastric wall was free of tumor infiltration. Microscopically, the lesion consisted of a relatively hypocellular proliferation of uniform spindle-shaped cells with vesicular nuclei and elongated eosinophilic cytoplasm. The stroma was loosely textured and myxoid, containing slit-like capillaries and scattered inflammatory infiltrates (Figure 3). Immunohistochemically, the tumor cells showed a complete absence of staining for SMA, DOG1, S100, CD34, desmin, and ALK (Figure 4). Additional immunohistochemical stains demonstrated a lack of STAT6 expression, absence of nuclear β‑Catenin accumulation, and retained SDHB expression (Figure 5), effectively excluding SFT, desmoid‑type fibromatosis, and SDH‑deficient mesenchymal neoplasms. Comprehensive molecular profiling, including targeted next-generation sequencing using the Agilent SureSelect XT HS2 custom panel (Agilent Technologies, Santa Clara, CA, USA), revealed no pathogenic alterations in any genes, including PDGFRA and KIT. In addition, RNA-based fusion transcript analysis using the Archer FusionPlex Sarcoma v2 panel (Integrated DNA Technologies, Coralville, IA, USA) identified no gene rearrangements. In light of the absence of a multinodular architecture and based on the combined histological, immunophenotypic, and molecular findings, the tumor was best classified as a uninodular PFM.

Figure 2 Macroscopic appearance. The tumor appears sectioned, uninodular, with a homogeneous, yellowish-white cut surface (A). The inset displays a close-up of the cut surface, showing no necrosis or hemorrhage (B).

Figure 3 Microscopic appearance. (A) Overview of the well demarked uninodular tumor. (B-D) Detail of the relatively hypocellular proliferation (B) of uniform spindle cells with vesicular nuclei and elongated eosinophilic cytoplasm (C) with a loose and myxoid background, punctuated by slit-like vessels and scattered inflammatory infiltrates (D). Hematoxylin and eosin staining; scale bar: A, 2 mm; B, 100 µm; C, 20 µm; D, 50 µm.

Figure 4 Immunohistochemical features. Complete absence of immunohistochemical expression for smooth muscle actin (A), DOG1 (B), CD34 (C), S100 (D), desmin (E), ALK (F). Scale bar: 100 µm. ALK, anaplastic lymphoma kinase; DOG1, discovered on gastrointestinal stromal tumor-1.

Figure 5 Immunohistochemical features. Complete absence of immunohistochemical expression of nuclear β-catenin (A) and STAT6 (B), with retained expression of SDHB (C). Scale bar: A, 100 µm; B, 100 µm; C, 20 µm. SDHB, Succinate Dehydrogenase Subunit B; STAT6, Signal Transducer and Activator of Transcription 6.

After discussion of the definitive pathology and confirmation of a benign entity without adverse histological features, no structured oncological follow-up program was recommended. The patient was contacted by telephone approximately 12 months post-resection and reported sustained well-being without gastrointestinal symptoms or clinical concerns, consistent with current evidence for the benign behavior of PFM.

All procedures performed in this study were in accordance with the ethical standards of the institutional and/or national research committee(s) and with the Declaration of Helsinki and its subsequent amendments. Written informed consent was obtained from the patient for the publication of this case report and accompanying images. A copy of the written consent is available for review by the editorial office of this journal.

Discussion

PFM represents an exceedingly rare mesenchymal neoplasm, with only 130 cases reported between 2007 and 2020 (8). While classical PFM typically exhibits multinodular, plexiform architecture with SMA positivity, our case represents an exceptional deviation from these hallmarks, showing both uninodular growth and complete absence of SMA expression in a 13 cm tumor without evidence of gastric wall infiltration.

Immunohistochemically, PFM typically expresses vimentin and SMA, while being negative for DOG1, CD117, desmin, CD34, S100, and ALK (1). Nuclear expression of the progesterone receptor has also been reported in some cases (1,4). Although SMA expression is considered characteristic, its absence, as in our case, does not preclude the diagnosis when supported by compatible histological and molecular findings (1). The uninodular architecture and the lack of SMA expression in this case expand the known histomorphologic and immunophenotypic spectrum of PFM. A comprehensive literature update from 2019 (4) reported complete SMA negativity in only 4 of 111 immunohistochemically evaluated cases (3.6%), while vimentin remained positive in all tested cases (100%). Uninodular growth represents an even rarer presentation, with only a single previously documented case with 10 mm that showed slow growth over 4 years (29). The present case is therefore exceptional in demonstrating the coexistence of SMA negativity and uninodular growth in a large 13 cm tumor, representing a diagnostic constellation that substantially increases the risk of misdiagnosis.

These atypical features posed a diagnostic challenge and initially raised suspicion for other mesenchymal neoplasms such as GIST, IFP, leiomyoma, plexiform neurofibroma, IMT, or even soft tissue sarcoma. Accurate differential diagnosis relies on a combined evaluation of morphology, immunohistochemistry, and molecular genetics. GISTs, which are significantly more common, typically express CD117 and DOG1 and harbor activating mutations in KIT or PDGFRA (1), features absent in our case. IFPs, while benign and occasionally myxoid, are usually CD34-positive (18,19). Histologically, they show a mixture of inflammatory cells, particularly eosinophils, together with epithelioid to spindled fibroblasts arranged in a characteristic perivascular onion-skin pattern but lack the distinct plexiform architecture of PFM (18). Like PFM, they tend to localize to the gastric antrum, but usually present as intraluminal, pedunculated submucosal polyps (19,20). The vast majority of IFPs harbor activating PDGFRA mutations, which are absent in PFM (19,20). IMTs typically occur in younger individuals and are characterized by ALK expression, frequent ALK or ROS1 rearrangements, and co-expression of SMA and desmin (30). Myxoid leiomyomas, while often morphologically similar, typically express desmin, which was negative in our case. Plexiform neurofibromas and schwannomas are strongly S100 and SOX10-positive and are usually distinguishable based on their neural histomorphology.

Molecular analysis plays an increasingly central role in distinguishing PFM from its histologic mimics. A recurrent translocation t(11;12)(q11;q13) involving MALAT1 and GLI1 has been described in 18–38% of PFMs (3,16). Although GLI1 fusions represent a recurrent molecular event in a subset of PFMs, their absence does not exclude the diagnosis and instead highlights the genetic heterogeneity of this entity. Additionally, inactivating mutations of the PTCH1 gene, implicating dysregulation of the Hedgehog signaling pathway, have been reported in a smaller subset (31). While some PFMs harbor MALAT1-GLI1 fusions or rare alterations such as PTCH1 inactivation or GLI1 polysomy (12q13) (16), most PFMs remain molecularly undefined, underscoring marked genetic heterogeneity. Our GLI1-negative tumor exemplifies this group and suggests that alternative genetic or epigenetic mechanisms may contribute to tumor development while maintaining the benign phenotype.

The complete absence of SMA expression in the present case raises mechanistic questions regarding myofibroblastic differentiation. SMA expression is largely regulated by TGF-β signaling, which, together with extracellular matrix composition and mechanical stress, promotes stable myofibroblast differentiation with persistent SMA expression (32). Disruption of TGF-β signaling or increased proliferative activity may destabilize this differentiation program (33), potentially explaining the loss of SMA expression. In this context, the selective loss of SMA in our case, combined with marked tumor growth, may reflect microenvironmental or signaling alterations that shift the cellular phenotype from myofibroblastic differentiation toward a more proliferative state.

Despite this phenotypic divergence and unusual tumor size, the lesion retained the benign biological behavior characteristic of PFM, highlighting the importance of correlating molecular findings with histological and immunophenotypic features. To date, PFM has not been associated with malignant transformation or metastatic behaviour, even in cases with ulceration or vascular invasion (1).

From a clinical perspective, recognizing PFM, particularly in its atypical presentations, is critical to avoid overtreatment. Misinterpretation as GIST could lead to unnecessary administration of tyrosine kinase inhibitors or excessively aggressive surgical management. Preoperative imaging may provide additional clues but remains challenging for definitive diagnosis. Differentiation between PFM and myxoid variants of GIST is often difficult, although several imaging features may raise suspicion. Reported PFMs frequently appear as well-circumscribed intramural or extraluminal mass with heterogeneous internal structure and gradual progressive enhancement on contrast‑enhanced CT or MRI, reflecting the myxoid tumor stroma. In contrast, GISTs more commonly present as larger, welldemarcated masses with a solid peripheral or rimlike enhancement surrounding areas of necrosis or cystic degeneration (34-36). In the present case, imaging revealed a large, well-circumscribed, heterogeneous mass in the gastric antrum with gradual enhancement and no marked diffusion restriction. Although these findings suggested a benign lesion, uncertainty regarding malignancy remained. Combined with endoscopic ultrasound findings, such imaging characteristics may prompt consideration of benign myxoid mesenchymal tumors such as PFM while emphasizing the need for definitive histopathologic and molecular confirmation.

Across reported cases spanning more than a decade, PFM has consistently demonstrated benign biological behavior, with no documented recurrences or metastases following complete resection (3,4,8). Comprehensive reviews describe follow-up periods with median durations of 15–52 months in cohorts of 55–130 patients, all of whom experienced uneventful clinical outcomes (4,8). Current evidence therefore supports stomach-preserving surgical approaches as the treatment of choice, ranging from local wedge resection to limited distal gastrectomy, provided that negative margins are achieved (1,8,37). In the present case, intraoperative assessment demonstrated a wellcircumscribed, extraluminal mass without invasion of the gastric wall or adjacent structures. Frozen section analysis confirmed negative margins, allowing a tangential wedge resection instead of radical gastrectomy and aligning with current recommendations to avoid overtreatment of this benign entity. No recurrence was observed during follow-up time, consistent with the favorable clinical course described for PFM. Nevertheless, given its rarity, the full biological potential of PFM remains uncertain. Until more data are available, complete surgical resection remains the standard of care (17).

Conclusions

This case illustrates the unique coexistence of uninodular architecture and complete absence of SMA expression in a massive PFM, expanding the recognized histological and immunophenotypic spectrum of this benign gastric tumor. It emphasizes the necessity of a multimodal diagnostic approach integrating histopathology, immunoprofiling, and molecular testing to ensure accurate diagnosis and avoid overtreatment. Given the absence of recurrence or metastatic potential in reported cases, complete surgical excision with negative margins remains the treatment of choice.

Acknowledgments

None.

Footnote

Reporting Checklist: The authors have completed the CARE reporting checklist. Available at https://acr.amegroups.com/article/view/10.21037/acr-2025-295/rc

Peer Review File: Available at https://acr.amegroups.com/article/view/10.21037/acr-2025-295/prf

Funding: None.

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://acr.amegroups.com/article/view/10.21037/acr-2025-295/coif). The authors have no conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. All procedures performed in this study were in accordance with the ethical standards of the institutional and/or national research committee(s) and with the Declaration of Helsinki and its subsequent amendments. Written informed consent was obtained from the patient for the publication of this case report and accompanying images. A copy of the written consent is available for review by the editorial office of this journal.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

References

1. Miettinen M, Makhlouf HR, Sobin LH, et al. Plexiform fibromyxoma: a distinctive benign gastric antral neoplasm not to be confused with a myxoid GIST. Am J Surg Pathol 2009;33:1624-32. [Crossref] [PubMed]
2. Takahashi Y, Shimizu S, Ishida T, et al. Plexiform angiomyxoid myofibroblastic tumor of the stomach. Am J Surg Pathol 2007;31:724-8. [Crossref] [PubMed]
3. Hu G, Chen H, Liu Q, et al. Plexiform fibromyxoma of the stomach: a clinicopathological study of 10 cases. Int J Clin Exp Pathol 2017;10:10926-33.
4. Su HA, Yen HH, Chen CJ. An Update on Clinicopathological and Molecular Features of Plexiform Fibromyxoma. Can J Gastroenterol Hepatol 2019;2019:3960920. [Crossref] [PubMed]
5. Moris D, Spanou E, Sougioultzis S, et al. Duodenal plexiform fibromyxoma as a cause of obscure upper gastrointestinal bleeding: A case report. Medicine (Baltimore) 2017;96:e5883. [Crossref] [PubMed]
6. Lin M, Song L, Qin S, et al. Plexiform fibromyxoma: Case report and literature review. Medicine (Baltimore) 2021;100:e27164. [Crossref] [PubMed]
7. Kang Y, Jung W, Do IG, et al. Plexiform angiomyxoid myofibroblastic tumor of the stomach: report of two cases and review of the literature. Korean J Pathol 2012;46:292-6. [Crossref] [PubMed]
8. Ma S, Wang J, Lu Z, et al. Plexiform fibromyxoma: a clinicopathological and immunohistochemical analysis of two cases with a literature review. J Int Med Res 2021;49:3000605211027878. [Crossref] [PubMed]
9. Tang J, Liu F. Plexiform Fibromyxoma: A Rare Mesenchymal Tumor Found in the Esophagus. Am J Gastroenterol 2020;115:648. [Crossref] [PubMed]
10. Ellis J UJ, Gonzalez R, Yin T, et al. Plexiform Fibromyxoma of the Colon: A Case Report. Clin Surg 2021;6:3122.
11. Fassan M, Salmaso R, Saraggi D, et al. Plexiform fibromyxoma of the gallbladder. Pathologica 2015;107:181-4.
12. Lu B, Ye W, Liu H. A Rare Gastric Tumor in a Young Woman. Gastric Plexiform Angiomyxoid Myofibroblastic Tumor. Gastroenterology 2015;149:294-5.
13. Schulz T, Drgac J, Chmelar C, et al. Plexiform angiomyxoid myofibroblastic tumour of the stomach. Pathologe 2012;33:65-9. [Crossref] [PubMed]
14. Tajima S, Ohata A, Koda K, et al. Myxoid epithelioid gastrointestinal stromal tumor harboring an unreported PDGFRA mutation: report of a case and review of the literature. Int J Clin Exp Pathol 2015;8:5821-9.
15. Higashi M, Hamada T, Sasaki K, et al. Esophageal plexiform fibromyxoma: A case report with molecular analysis for MALAT1-GLI1 fusion. Pathol Res Pract 2022;233:153878. [Crossref] [PubMed]
16. Spans L, Fletcher CD, Antonescu CR, et al. Recurrent MALAT1-GLI1 oncogenic fusion and GLI1 up-regulation define a subset of plexiform fibromyxoma. J Pathol 2016;239:335-43. [Crossref] [PubMed]
17. Di Mauro A, Rega RA, Leongito M, et al. Plexiform Fibromyxoma in the Stomach: Immunohistochemical Profile and Comprehensive Genetic Characterization. Int J Mol Sci 2024;25:4847. [Crossref] [PubMed]
18. Calderon MG, Caivano VC, Bagnaresi S Jr, et al. A unique case of inflammatory fibroid polyp in the duodenum of a female adolescent: Case report and literature review. Medicine (Baltimore) 2017;96:e6131. [Crossref] [PubMed]
19. Manley PN, Abu-Abed S, Kirsch R, et al. Familial PDGFRA-mutation syndrome: somatic and gastrointestinal phenotype. Hum Pathol 2018;76:52-7. [Crossref] [PubMed]
20. Hodan R, Charville GW, Ladabaum U. Hereditary inflammatory fibroid polyps caused by germline pathogenic variants in PDGFRA: Refining PDGFRA-mutation syndrome. Cancer Genet 2021;256.
21. Billings SD, Hogendoorn PW. Leiomyoma. In: WHO Classification of Tumours Editorial Board, editor. Soft tissue and bone tumours. WHO classification of tumours series. 5 ed. Lyon (France): International Agency for Research on Cancer; 2020.
22. Wang QA, Wu RC, Lee CW, et al. Clinicopathological Features and Immunochemical Staining of Inflammatory Myofibroblastic Tumor: A Retrospective Study of 48 Cases. Anal Cell Pathol (Amst) 2025;2025:4948627. [Crossref] [PubMed]
23. Demicco EG, Wagner MJ, Maki RG, et al. Risk assessment in solitary fibrous tumors: validation and refinement of a risk stratification model. Mod Pathol 2017;30:1433-42. [Crossref] [PubMed]
24. Chmielecki J, Crago AM, Rosenberg M, et al. Whole-exome sequencing identifies a recurrent NAB2-STAT6 fusion in solitary fibrous tumors. Nat Genet 2013;45:131-2. [Crossref] [PubMed]
25. Demicco EG, Harms PW, Patel RM, et al. Extensive survey of STAT6 expression in a large series of mesenchymal tumors. Am J Clin Pathol 2015;143:672-82. [Crossref] [PubMed]
26. Garrett A, Loveday C, King L, et al. Quantifying evidence toward pathogenicity for rare phenotypes: The case of succinate dehydrogenase genes, SDHB and SDHD. Genet Med 2022;24:41-50. [Crossref] [PubMed]
27. Ibrahim A, Chopra S. Succinate Dehydrogenase-Deficient Gastrointestinal Stromal Tumors. Arch Pathol Lab Med 2020;144:655-60. [Crossref] [PubMed]
28. Riedel RF, Agulnik M. Evolving strategies for management of desmoid tumor. Cancer 2022;128:3027-40. [Crossref] [PubMed]
29. Kobori I, Katayama Y, Hayashi K, et al. Uninodular Fibromyxomatous Gastric Tumor Resected by Endoscopic Submucosal Dissection. Intern Med 2019;58:2015-8. [Crossref] [PubMed]
30. Hornick JL, Oda Y. Inflammatory myofibroblastic tumour. In: WHO Classification of Tumours Editorial Board, editor. Soft Tissue and Bone Tumours. WHO Classification of Tumours series. 5th ed. Lyon (France): International Agency for Research on Cancer; 2020.
31. Banerjee S, Corless CL, Miettinen MM, et al. Loss of the PTCH1 tumor suppressor defines a new subset of plexiform fibromyxoma. J Transl Med 2019;17:246. [Crossref] [PubMed]
32. Catteau X, Simon P, Noel JC. Myofibroblastic stromal reaction and lymph node status in invasive breast carcinoma: possible role of the TGF-beta1/TGF-betaR1 pathway. BMC Cancer 2014;14:499. [Crossref] [PubMed]
33. Scharenberg MA, Pippenger BE, Sack R, et al. TGF-beta-induced differentiation into myofibroblasts involves specific regulation of two MKL1 isoforms. J Cell Sci 2014;127:1079-91. [Crossref] [PubMed]
34. Yang MX, Zhao ZH, Yang JF, et al. Imaging findings of gastric plexiform fibromyxoma with a cystic change: A case report and review of literature. Medicine (Baltimore) 2017;96:e8967. [Crossref] [PubMed]
35. Arslan ME, Li H, Fu Z, et al. Plexiform fibromyxoma: Review of rare mesenchymal gastric neoplasm and its differential diagnosis. World J Gastrointest Oncol 2021;13:409-23. [Crossref] [PubMed]
36. Sakamoto K, Hirakawa M, Atsumi K, et al. A case of gastric plexiform fibromyxoma: radiological and pathological findings. Jpn J Radiol 2014;32:431-6. [Crossref] [PubMed]
37. Wu JD, Chen YX, Luo C, et al. Plexiform angiomyxoid myofibroblastic tumor treated by endoscopic submucosal dissection: A case report and review of the literature. World J Gastroenterol 2021;27:5288-96. [Crossref] [PubMed]