Plexiform Fibromyxoma in the Stomach: Immunohistochemical Profile and Comprehensive Genetic Characterization.

Plexiform fibromyxoma (PF), also referred to as plexiform angiomyxoid myofibroblast tumor, is an exceedingly rare mesenchymal neoplasm primarily affecting the stomach. Herein, we present a case of PF diagnosed in a 71-year-old male with a history of lung cancer, initially suspected to have a gastrointestinal stromal tumor (GIST) of the stomach, who subsequently underwent subtotal gastrectomy. The histopathological and molecular features of the tumor, including mutations in ABL1, CCND1, CSF1R, FGFR4, KDR, and MALAT1-GLI1 fusion, are elucidated and discussed in the context of diagnostic, prognostic, and therapeutic considerations.

Viscus perforation as an initial presentation of plexiform fibromyxoma: A case report and review of the literature.

INTRODUCTION: Plexiform fibromyxoma (PF) is a rare benign mesenchymal neoplasm of stomach recognized by the WHO. The tumor often arises in the antrum and pyloric region of the stomach. Morphologically, PF tumors display bland spindle cells in myxoid or fibromyxoid stroma and can be misdiagnosed as gastrointestinal stromal tumor (GIST). PRESENTATION OF CASE: A-21-year old female presented to emergency department with peritonitis due gastric tumor leading to gastric perforation and pus collection in the abdomen. Partial gastrectomy was performed. Histopathology, immunohistochemical (IHC) and fluorescent in-situ hybridization assessment of the specimen confirmed the diagnosis of PF. One year postoperative, the patient remains symptoms free. CLINICAL DISCUSSION: A great majority of gastric mesenchymal tumors are GIST. Histopathologically, PF tumors display a multinodular and plexiform architecture with arborizing vasculature. Cytologically these tumors show bland spindle cells in myxoid or fibromyxoid stroma with a rare or no mitotic figures. Thus, PF may easily be under recognized or misinterpreted without the pathologists' knowledge of this entity. Misinterpreting PF as GIST can lead to inappropriate treatment including unnecessary surgery and/or chemotherapy, which is an expensive. Recommended treatment is surgical excision. Metastases and recurrence following complete excision have not been described. This case highlights unexpected presentation in a young female where other competing diagnoses were more plausible before considering PF diagnosis which could not have been established without advanced diagnostic techniques. CONCLUSION: PF is a rare mesenchymal tumor with nonspecific clinical characteristics. It is principally located in the gastric antrum and prepyloric regions, however other parts of the body may be affected. PF tumors should be separated from GIST, nerve sheath tumors, and other fibromyxoid neoplasms. The worth in writing lies in epidemiological custodianship for such a unique presentation of a rare gastric neoplasm.

MALAT1 functions as a transcriptional promoter of MALAT1::GLI1 fusion for truncated GLI1 protein expression in cancer.

BACKGROUND: The long non-coding RNA metastasis-associated lung adenocarcinoma transcript 1 (MALAT1) is a cancer biomarker. Furthermore, fusion of the MALAT1 gene with glioma-associated oncogene 1 (GLI1) is a diagnostic marker of plexiform fibromyxoma and gastroblastoma; however, the function of this fusion gene remains unexplored. METHOD: In this study, we elucidate the structure and function of the MALAT1::GLI1 fusion gene. To this end, we determined a transcriptional start site (TSS) and promoter region for truncated GLI1 expression using rapid amplification of the 5' cDNA end and a luciferase reporter assay in cultured cells transfected with a plasmid harboring the MALAT1::GLI1 fusion gene. RESULTS: We found that the TATA box, ETS1 motif, and TSS were located in MALAT1 and that MALAT1 exhibited transcriptional activity and induced expression of GLI1 from the MALAT1::GLI1 fusion gene. Truncated GLI1, lacking SUMOylation and SUFU binding sites and located in the nucleus, upregulated mRNA expression of GLI1 target genes in the hedgehog signaling pathway. CONCLUSIONS: We demonstrate a distinct and alternative function of MALAT1 as a transcriptional promoter for expression of the MALAT1::GLI1 fusion gene. Our findings will aid future research on MALAT1 and its fusion gene partners.

Endoscopic submucosal excavation for gastric plexiform fibromyxoma: A case report and systematic review of literature.

Plexiform fibromyxoma (PF) is a rare mesenchymal tumor of which the pathogenesis and molecular changes are still unclear. Histologically, it is characterized by a cluster of bland spindle or ovoid cells growing in the mucoid or fibromyxoid stroma rich in small blood vessels. At present, surgical resection is the primary treatment for PF.

Plexiform fibromyxoma of the stomach: An underrecognized entity!

Plexiform fibromyxoma (PF) is a recently described rare type of mesenchymal tumor of the stomach with only 123 cases reported in the literature. It is characterized by a peculiar plexiform growth pattern, myxoid stroma with arborizing microvasculature, and spindle-shaped myofibroblastic cells. We herein report a case of gastric PF in a 15-year-old boy, mimicking a gastrointestinal stromal tumor (GIST) due to overlapping clinicoradiological features. Distinct pathological and immunohistochemical features of PF do aid in distinction from GIST and other mesenchymal entities. Diagnosis is crucial as surgical resection is the mainstay of treatment unlike aggressive management in GIST. It is a benign entity with no local recurrence or distant metastasis reported so far, but confirmation of the same requires longitudinal observational studies with a larger sample size.

Gastric Plexiform Fibromyxoma Resected Using Nonexposed Endoscopic Wall-Inversion Surgery: A Case Report.

Gastric plexiform fibromyxoma is extremely rare. In our case, upper gastrointestinal endoscopy of a 41-year-old woman patient revealed a 1-cm submucosal tumor (SMT) in the greater curvature of the lower body of the stomach. On contrast-enhanced computed tomography, the tumor was hypervascular in the arterial phase with continuous enhancement in the post-venous phase. On endoscopic ultrasonography, it had a low echo pattern. The preoperative diagnosis was a gastric SMT with a rich vasculature; however because the biosy specimen did not contain tumor tissue, a malignant tumor could not be excluded. The patient underwent nonexposed endoscopic wall-inversion surgery (NEWS), and the tumor was completely resected. Immunohistochemical examination revealed that the tumor was positive for D2-40 and α-smooth muscle actin, but negative for c-kit, discovered on gastrointestinal stromal tumor-1, desmin, S100, Melan-A, signal transducer and activator of transcription 6, insulinoma-associated protein 1, CXCL13, ETS transcription factor, follicular dendritic cell, anaplastic lymphoma kinase, human melanoma black, h-caldesmon, and CD1a, 10, 21, 23, 31, 34, 68, and 163. Approximately, 1-2% of the tumor cell nuclei were Ki-67-positive. Finally, we diagnosed the tumor as a plexiform fibromyxoma. In conclusion, NEWS is an effective method for the treatment of SMTs with a diameter of <3 cm.

Esophageal plexiform fibromyxoma: A case report with molecular analysis for MALAT1-GLI1 fusion.

Plexiform fibromyxoma (PFM) is a rare gastrointestinal tract tumor that develops in the stomach in most cases. Here, we report an extremely rare case of esophageal PFM. A female in her mid-30 s presented with difficulty in swallowing and breathing. Endoscopic examination revealed a submucosal tumor measuring approximately 45 × 50 mm in the upper thoracic esophagus. The biopsied specimen did not show definite histological evidence of gastrointestinal stromal tumors (GISTs). Since imatinib administration based on a clinical diagnosis of GIST did not show a therapeutic effect for tumor reduction, tumor resection was performed. The resected tumor exhibited proliferation of spindle tumor cells with abundant myxoid and vascular stroma separated by a muscular layer, indicating a plexiform arrangement. Immunohistochemical analysis demonstrated that the tumor cells diffusely expressed vimentin and alpha-smooth muscle actin, but not desmin, c-kit, DOG1, and CD34. MALAT1-GLI1 fusion was detected in formalin-fixed paraffin-embedded tissue using RT-PCR and Sanger sequencing. The results suggested that a fibromyxoid tumor can develop in the esophagus, showing an identical histology and MALAT1-GLI1 fusion to gastric PFM.

Huge gastric plexiform fibromyxoma presenting as pyemia by rupture of tumor: A case report.

BACKGROUND: Plexiform fibromyxoma (PF) is a rare mesenchymal tumor, with limited case reports worldwide. Common clinical symptoms are abdominal discomfort and bleeding signs, which frequently present slow-onset in reported cases. Herein, we report a case of gastric PF presenting as acute onset and with pyemia accom-panying tumor rupture. We resected the tumor as well as the distal gastric, bulbus duodeni and gallbladder for treatment in emergency surgery. Notably, before the onset of the disease, the patient received coronavirus disease 2019 (COVID-19) vaccines. CASE SUMMARY: A 26-year-old man was admitted to our hospital, due to abdominal pain and fever after having received COVID-19 vaccines. Laboratory examination indicated severe sepsis. Computed tomography scan revealed a large mass in the abdomen. Deformation of the gastrointestinal tract was seen during gastroscopy. After failure of anti-infective treatment and symptoms of shock developed, he received an emergency surgery. We found a huge and partly ruptured mass, with thick purulence. Microscopically, the mass was composed of spindle cells with clarified cytoplasm, accompanied by myxoid stroma and arborizing blood vessels. Immunohistochemistry showed the tumor cells as positive for smooth muscle actin and succinate dehydrogenase subunit B but negative for DOG-1 and CD117. Finally, the patient was diagnosed with gastric PF and discharged from the hospital. CONCLUSION: Gastric PF manifesting as tumor rupture combined with pyemia is rare. Timely surgery is critical for optimal prognosis.

Spontaneous hemoperitoneum as a rare presentation of gastric lesions: Two case reports.

INTRODUCTION: Spontaneous hemoperitoneum is a rare but life-threatening condition. Clinical presentation is usually nonspecific. The aim of this report is to document a rare clinical presentation of two different intramural stomach tumors. CLINICAL CASES: A 40-year-old patient with 24 h epigastric pain was admitted to the emergency, pale, with signs of peritoneal irritation. Computed tomography showed an hemoperitoneum with active bleeding in the posterior wall of the stomach. A wedge resection was performed. Histological report revealed a plexiform fibromyxoma (PF). The second case presents a 79-year-old patient with 24 h abdominal pain, fullness and dizziness, pale and with signs of peritoneal irritation. A voluminous exophytic lesion on gastric wall with active bleeding was diagnosed. Wedge resection was performed and histological report demonstrated a gastrointestinal stromal tumor (GIST). DISCUSSION: Imaging plays a role in the diagnosis of spontaneous hemoperitoneum, in elucidating a cause and detecting active hemorrhage. Tumor hemorrhage may be the first presentation of an underlying mass. The presence of a bleeding gastric mass of uncertain nature may result in a challenging situation for the surgeon, who is forced to perform a gastric resection without knowing the exact nature of the tumor and hence the extent of gastric resection required. To our knowledge, our case is the first of PF presenting as hemoperitoneum. Hemoperitoneum is rare as first presentation of GIST, with few cases reported in literature. CONCLUSION: We report two extremely rare cases of spontaneous hemoperitoneum as first presentation of gastric tumor. For the diagnosis a high level of suspicion is required.

Plexiform fibromyxoma: a clinicopathological and immunohistochemical analysis of two cases with a literature review.

OBJECTIVE: This article aimed to study the clinicopathological features, immunophenotypes, and differential diagnoses of plexiform fibromyxoma (PF). METHODS: We searched clinical and pathology databases of our hospital for patients with histologically confirmed PF from 2007 to 2020 and reviewed the relevant English and Chinese language literature. RESULTS: Two cases of PF were identified, a 67-year-old woman and a 23-year-old man. Both patients presented with melena and anemia and underwent partial gastrectomy. Histologically, the tumors exhibited a plexiform growth pattern in the gastric submucosa and the presence of bland-looking spindle cells in the fibromyxoid stroma with the formation of small blood vessels. Immunohistochemically, the two cases were strongly positive for vimentin, smooth muscle actin, and muscle-specific actin and negative for CD117, discovered on gastrointestinal stromal tumors protein 1, CD34, CD10, S100, desmin, H-caldesmon, estrogen receptor, progesterone receptor, ß-catenin, and cytokeratin. CONCLUSIONS: PF is a rare mesenchymal tumor of the stomach that can be distinguished from other gastrointestinal mesenchymal tumors based on its distinctive morphology and immunophenotype.

Gastric Plexiform Fibromyxoma with Two Different Growth Patterns on Histological Images: a Case Report.

Plexiform fibromyxoma (PF) of the stomach is a very rare mesenchymal tumor of the gastrointestinal tract. We report the first case of PF with 2 different growth patterns pathologically confirmed after surgical resection. The tumor was characterized microscopically as infiltrative; it demonstrated diffuse growth into the smooth muscle bundles of the muscularis propria and was also multinodular and plexiform within the myxoid stroma. Immunohistochemical analysis revealed that the tumor cells were positive or weakly positive for smooth muscle actin, vimentin, and H-caldesmon and negative for desmin, CD117, CD34, CK-20, Pan-CK, Dog1, S100, ER, PR, and CD10. No mutations of C-kit and platelet-derived growth factor receptor alpha were detected. No genetic disruption of glioma-associated oncogene homolog 1 was detected by fluorescence in situ hybridization. The final diagnosis of PF was mainly based on the morphological and immunohistochemical findings.

Gastric plexiform fibromyxoma: A case report.

BACKGROUND: Plexiform fibromyxoma (PF) is a rare mesenchymal tumor of the stomach. The clinical features of PF frequently include upper abdominal pain, abdominal discomfort, hematemesis, melena, pyloric obstruction and an upper abdominal mass. We herein report a case of PF resected by laparoscopic radical distal gastrectomy plus Roux-en-Y gastrojejunostomy. CASE SUMMARY: The patient was admitted to hospital, due to a 1-wk history of an abdominal space-occupying lesion identified during a health examination. He underwent complete resection by laparoscopic radical distal gastrectomy plus Roux-en-Y gastrojejunostomy. During the operation, the tumor was located in the anterior wall of the gastric antrum (approximately 7 cm × 6 cm × 5.5 cm) and did not show evidence of invasion of the serosa. Histology showed that the tumor cells were oval fibroblast-like and spindle-shaped cells, with numerous thin-walled blood vessels and abundant myxoid stroma. Cellular atypia and mitosis were both rare. Immunohistochemistry showed that the tumor cells were immunoreactive for smooth muscle actin, S-100 and CD-10, but were negative for CD-117, CD-34, DOG-1, and ALK. In this case, S-100 was positive and no significant disease was observed during the follow-up period. CONCLUSION: The fact that PF is a rare tumor with only a few cases in this region can lead to misdiagnosis of this entity and pose a real diagnostic challenge for general surgeons and pathologists when encountering such patients and differentiating PF from other primary tumors of gastric mesenchymal origin. Our report may help increase awareness of this rare, but important new disease entity.

A rare case of plexiform fibromyxoma in stomach: FNA diagnosis with histological correlation and differential diagnoses.

Plexiform angiomyxoma (PF) is a rare benign mesenchymal neoplasm that arises in the antrum and pyloric region of the stomach. To the best of our knowledge, there are only two prior endoscopic ultrasound guided fine needle aspiration cytology examples have been reported. We report a case of PF which was diagnosed via EUS FNA and later confirmed on resection specimen. Differential diagnoses of this tumor are discussed. Although diagnosis of plexiform fibromyxoma on FNA specimen is difficult, a good FNA specimen with subsequent careful morphological evaluation and immunohistochemical staining work-up makes this task possible.

Rare mesenchymal antral gastric tumors: Case reports of glomus tumor and plexiform fibromyxoma.

Gastrointestinal stromal tumors account for the majority of the mesenchymal neoplasms of the gastric antrum, but other entities should also be considered. We present the case of a 70-year-old man with an ulcerated well-circumscribed polypoid submucosal mass in the gastric antrum which was proven to be a glomus tumor. CT showed progressive contrast enhancement. Magnetic resonance imaging showed a high T2 signal intensity and heterogeneous arterial contrast enhancement which became more homogeneous in later phases. We also present the case of a 50-year-old woman with a large polypoid mass occupying half the circumference of the distal gastric antrum that was proven to be a plexiform fibromyxoma. Contrast-enhanced CT and magnetic resonance imaging revealed a pattern of progressive and heterogeneous enhancement. Although gastrointestinal stromal tumors are the most frequent gastric mesenchymal neoplasms, other rare mesenchymal tumors such as glomus tumor and plexiform fibromyxoma may arise in the gastric antrum.

Gastric Plexiform Fibromyxoma: A Great Mimic of Gastrointestinal Stromal Tumor (GIST) and Diagnostic Pitfalls.

Through a multicenter study, we collected seven cases of gastric plexiform fibromyxoma including four females and three males, 21 to 79 y old (46.1 ± 10.1). All cases showed a unilocular lesion measuring 0.3 to 17 cm (5.3 ± 2.4), arising from antrum (5/7) or body (2/7). Six of the seven cases had intraoperative frozen sections and/or endoscopic ultrasound fine needle aspiration (EUS-FNA), and all of them were preoperatively or intraoperatively diagnosed as gastrointestinal stromal tumor (GIST). EUS-FNA material showed markedly elongated spindle cells with streaming oval to elongated nuclei with rounded ends. Histologically, the tumors exhibited a plexiform growth pattern and were composed of a rich myxoid stroma and cytologically bland uniform spindle cells without mitotic figures, with the exception of one case which displayed nuclear pleomorphism and increased mitosis. Immunostains showed the tumor cells to be focally positive for SMA (6/6), focally and weakly positive for desmin (3/6) and caldesmon (2/3), negative for CD117 (0/7), CD34 (0/7), DOG1 (0/4), and S100 (0/5). No mutations were identified on Next-Generation Sequencing test, and no loss of SDHB immunoreactivity was identified in the tumor with nuclear pleomorphism. One case was treated with Gleevec because of the initial diagnosis of GIST. All patients had a follow-up for up to 11 y, with no tumor recurrence or metastasis reported. Our results suggest that gastric plexiform fibromyxoma is rare and may be underrecognized and misinterpreted as GIST during intraoperative frozen section or preoperative EUS-FNA diagnosis without immunostains leading to inappropriate treatment.

Plexiform fibromyxoma of the small bowel: A case report.

BACKGROUND: Plexiform fibromyxoma is a rare, special type of mesenchymal tumor. The most common presenting symptoms are anemia, hematemesis, and hematochezia, without sex or age predilection. The reported cases have mainly occurred in the gastric antrum and pylorus region, with some cases in the duodenum. CASE SUMMARY: We report here a case of plexiform fibromyxoma in the upper segment of the jejunum, which was continuously followed up for 3 years after surgical removal. Plexiform fibromyxoma showed multinodular or plexiform growth. The cells in the tumor node were spindle-shaped but few in number and mitotic figures. Small blood vessels and mucous matrix were found among the tumor cells. Immunohistochemistry revealed that the plexiform fibromyxoma cells were positive for smooth muscle actin, focally positive for CD10, and negative for cytokeratin, CD117, DOG-1 (discovered on GIST-1) desmin, S-100, epithelial membrane antigen, and CD34. Ki-67 labeling index was < 5%. Plexiform fibromyxoma showed benign biological behavior. After 3 years of consecutive postoperative follow-up, no obvious signs of metastasis or recurrence were found by imaging examination. CONCLUSION: Plexiform fibromyxoma is a rare type of mesenchymal tumor. The diagnosis mainly depends on pathological examination, and it should be distinguished from other gastrointestinal mesenchymal tumors.

Endoscopic ultrasound FNA: An illustrated review of spindle cell neoplasms of the upper gastrointestinal tract including a novel case of gastric plexiform fibromyxoma.

Plexiform fibromyxoma (PF) is a recently-described and rare mesenchymal neoplasm of the gastric wall. A few small case series reports of this spindle cell entity exist in the surgical pathology literature, but to our knowledge no prior endoscopic ultrasound guided fine needle aspiration cytology examples have been reported. In clinical practice, mural gastrointestinal (GI) lesions are often initially evaluated by endoscopic ultrasound guided (EUS) fine needle aspiration (FNA). In addition, newer EUS fine needle biopsy techniques also allow for reliable retrieval of core tissue samples with intact cellular architecture, making EUS histopathologic analyses possible. We report a combined EUS FNA and core biopsy case of PF and correlate the findings with imaging results. The cytomorphology of PF is described and illustrated, and important entities in the differential diagnosis of upper GI spindle cell lesions (including GI stromal tumor, leiomyoma, schwannoma, carcinoid tumor, desmoid-type fibromatosis, and inflammatory fibroid polyp) are reviewed. Illustrated examples of relevant cytomorphologic, cell block histomorphologic and immunohistochemical characteristics are emphasized.