Plexiform angiomyxoid myofibroblastic tumor treated by endoscopic submucosal dissection:A case report and review of the literature

BACKGROUND Plexiform angiomyxoid myofibroblastic tumor(PAMT)is a rare mesenchymal tumor characterized by multiple nodular plexiform growth patterns and an immunophenotype with myofibroblasts.The pathological characteristics,immunohistochemistry,diagnostic criteria,differential diagnosis,and gene-level changes of PAMT have been reported in many studies.At present,the main treatment for PAMT in the reported cases is surgery;only eight cases were treated via endoscopy(excluding 1 thoracoscopic resection),and the lesions were all smaller than 5 cm.There are no reports on the prognosis and follow-up of young patients with lesion sizes reaching 5 cm who undergo endoscopic submucosal dissection(ESD).Herein,we present the first case of a young patient with a lesion size reaching 5 cm who was diagnosed with PAMT via endoscopic submucosal dissection.CASE SUMMARY A 15-year-old young man with upper abdominal pain for 2 years presented to the Gastroenterology Department of our hospital.Painless gastroscopy showed a semicircular bulge approximately 5 cm in size in the lesser curvature near the cardia of the fundus;the surface was eroded,and shallow ulcers had formed.The pathological manifestations of the biopsy were spindle cell proliferative lesions with interstitial mucinous changes,and the surface mucosa showed chronic inflammatory changes with active lesions;immunohistochemistry showed smooth muscle actin(SMA)(+),CD117(-),CD34(-),DOG-1(-),S-100(-),and Ki67(LI:<1%).We performed ESD on the patient.The lesion that we removed was 5 cm×4 cm×2 cm in size.Pathologically,the resected tissue displayed typical manifestations,such as fat spindle-shaped fibroblasts and myofibroblast-like cells showing irregular nodular hyperplasia.Immunohistochemistry staining of the tumor cells revealed the following:CD34(partially+),SMA(weakly+),CD117(-),DOG-1(-),S-100(-),SDHB(+),PCK(-),and Ki67(labelling index:2%).There was no recurrence or metastasis during the 3-mo follow-up after the operation,and the treatment effect was good.We also performed a review of the literature on the clinical manifestations,pathological features,immunohistochemistry,and differential diagnosis of PAMT.CONCLUSION At present,the diagnostic criteria for PAMT are relatively clear,but the pathogenesis and genetic changes require further study.PAMT is benign in nature,and these patients are less likely to experience local or metastatic recurrence.The main treatment is still surgery if the lesion is in the stomach.Partial gastrectomy and distal gastrectomy are the most frequently performed surgical treatments for PAMT,followed by local resection,subtotal gastrectomy,and wedge resection.But for comprehensive evaluation of the disease,ESD can be considered a suitable method to avoid excessive treatment.

A rare case of plexiform angiomyxoid myofibroblastic tumor in the stomach which was diagnosed at the earliest stage in the literature

Plexiformangiomyxoid myofibroblastic tumor(PAMT)is a rare gastric mesenchymal entity with a peculiar plexiform pattern,bland spindle cells and myxoid stroma rich in arborizing blood vessels.Here we report a 44-year-old Chinese woman with PAMT.Initially she was admitted for removal of a gastric antral‘polyp’found on a routine examination 5 months previously.Our gastroscopy showed a 0.80.8cm polyp-like mass in the antrum which protruded into the lumen.Endoscopic submucosal dissection(ESD)was performed to remove this mass en bloc.The specimen was carefully examined by pathologists,and the correct diagnosis of PAMT was finally made.The tumor in this case depicted typical histopathological and immunohistochemical features of gastric PAMT.This PAMT was not only the smallest on endoscopic examination in the literature but also—unlike the already reported PAMTs—exhibited a focal hyperechogenic lesion on endoscopic ultrasonography(EUS).This information highlights its value on how to identify a PAMT at its early stage.

Plexiform angiomyxoid myofi broblastic 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.

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 followup, 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 aggressivebehavior. 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.