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.

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.

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.

Plexiform fibromyxoma of the stomach: a clinicopathological study of 10 cases

Plexiform fibromyxoma (PF) is a unique mesenchymal tumor of the stomach. The molecular characteristics of these tumors remain unclear. Here, we report 10 cases of PF with clinicopathological features and molecular features in detail. The patients ranged in age from 26 to 72 years (mean, 49 y) and most commonly presented with abdominal pain and distension, black stool, and anemia. Eight tumors were located at the antrum while two in the fundus of stomach. Histologically, tumor cells exhibited a plexiform growth pattern with multiple nodules in the muscularis propria of stomach wall and infiltrative borders. Immunohistochemically, all tumors were strongly positive for vimentin and smooth muscle actin (SMA), some were staining for CD10 (5/10), desmin (5/10), H-caldesmon (6/10) and progesterone receptor (PR, 6/10), however, CD34, S-100, Estrogen Receptor (ER), ALK, CD117 and DOG-1 were all negative in our cases. The glioma-associated oncogene homologue 1 (GLI1) gene translocation was detected in eight cases by FISH with three positive and five negative. Mutation analyses of C-KIT and platelet-derived growth factor receptor alpha (PDGFRA) genes were performed on five cases and all of which were wild-type for mutation. Our follow-up indicated that all of the patients made an uneventful recovery at 24 to 95 months after diagnosis. In summary, the distinctively histological features and immunohistochemical positivity of SMA, CD10 and PR can help differentiate PF from other gastrointestinal mesenchymal tumors. GLI1 gene translocation offers an additional molecular instrument for the diagnosis. The expression of PR and the existence of GLI1 gene translocation in PF highlights of our article.

Rarity among benign gastric tumors: Plexiform fibromyxoma - Report of two cases

Plexiform fibromyxoma is a very rare mesenchymal tumor of the stomach, found almost exclusively in the antrum/pylorus region. The most common presenting symptoms are anemia, hematemesis, nausea and unintentional weight loss, without sex or age predilection. We describe here two cases of plexiform fibromyxoma, involving a 16-year-old female and a 34-year-old male. Both patients underwent complete resection (R0) by distal gastrectomy and retrocolic gastrojejunostomy (according to Billroth 2); for both, the postoperative course was uneventful. Histology showed multiple intramural and subserosal nodules with characteristic plexiform growth, featuring bland spindle cells situated in an abundant myxoid stroma with low mitotic activity. Immunohistochemistry showed α-smooth muscle actin-positive spindle cells, focal positivity for CD10, and negative staining for KIT, DOG1, CD34, S100, β-catenin, STAT-6 and anaplastic lymphoma kinase. One of the cases showed focal positivity for h-caldesmon and desmin. Upon follow-up, no sign of disease was found. In the differential diagnosis of plexiform fibromyxoma, it is important to exclude the more common gastrointestinal stromal tumors as they have greater potential for aggressive behavior. Other lesions, like neuronal and vascular tumors, inflammatory fibroid polyps, abdominal desmoid-type fibromatosis, solitary fibrous tumors and smooth muscle tumors, must also be excluded.

Gastric plexiform fibromyxoma resected by endoscopic submucosal dissection after observation of chronological changes: A case report

A 66-year-old man was diagnosed with a gastric submucosal tumor. Endoscopic ultrasound (EUS) revealed an iso/hypoechoic mass in the third layer. No malignant cells were detected in a histological examination. Yearly follow-up endoscopy and EUS showed the slow growth of the tumor. Endoscopic submucosal dissection (ESD) was performed and a glistening tumor was resected. The lesion showed a multinodular plexiform growth pattern consisting of spindle cells with an abundant fibromyxoid stroma that was rich in small vessels. The tumor was diagnosed as plexiform fibromyxoma (PF) by immunohistochemistry. Although difficulties are associated with reaching a diagnosis preoperatively, chronological changes on EUS may contribute to the diagnosis of PF. ESD may also be useful in the diagnosis and treatment of PF.

Plexiform fibromyxoma of the stomach: Report of one case and review of the literature

Plexiform fibromyxoma (PF) of the stomach is a recently described rare mesenchymal neoplasm of the gastrointestinal tract. Its main clinical features include a peculiar plexiform pattern, bland spindle cells and a myxoid stroma rich in arborizing blood vessels. However, the epidemiology, etiology, pathogenesis, diagnosis and treatment of PF are still not very clear. Here we report a case of plexiform fibromyxoma of the stomach, and we also performed a literature review.

Plexiform angiomyxoid myofibroblastic tumor of the stomach

Plexiform angiomyxoid myofibroblastic tumor of the stomach is a unique mesenchymal tumor that we first described in 2007. The tumor is very rare, and to date, only 18 cases confirmed by immunohistochemistry have been reported in the literature. The patients’ ages ranged from 7 to 75 years (mean, 43 years), and the male-to-female ratio was approximately 1:1. Representative clinical symptoms are ulceration, associated upper gastrointestinal bleeding (hematemesis), and anemia. The tumors are located at the antrum in all cases, and grossly, the tumor is whitish to brownish or reddish, and forms a lobulated submucosal or transmural mass. Microscopically, the tumor is characterized by a plexiform growth pattern, the proliferation of cytologically bland spindle cells, and a myxoid stroma that is rich in small vessels and positive for Alcian blue stain. Immunohistochemically, the tumor cells are positive for α-smooth muscle actin and negative for KIT and CD34. Differential diagnoses include gastrointestinal stromal tumor and other mesenchymal tumors of the gastrointestinal tract. Some authors proposed that this tumor should be designated as “plexiform fibromyxoma”, but this designation might cause confusion. The tumor is probably benign and thus far, neither recurrence nor metastasis has been reported.