Plexiform fibromyxoma:Review of rare mesenchymal gastric neoplasm and its differential diagnosis

Plexiform fibromyxoma(PF)is a very rare mesenchymal neoplasm of the stomach that was first described in 2007 and was officially recognized as a subtype of gastric mesenchymal neoplasm by World Health Organization(WHO)in 2010.Histologically,PF is characterized by a plexiform growth of bland spindle to ovoid cells embedded in a myxoid stroma that is rich in small vessels.The lesion is usually paucicellular.While mucosal and vascular invasion have been documented,no metastasis or malignant transformation has been reported.Its pathogenesis is largely unknown and defining molecular alterations are not currently available.There are other mesenchymal tumors arising in the gastrointestinal tract that need to be differentiated from PF given their differing biologic behaviors and malignant potential.Histologic mimics with spindle cells include gastrointestinal stromal tumor,smooth muscle tumor,and nerve sheath tumor.Histologic mimics with myxoid stroma include myxoma and aggressive angiomyxoma.Molecular alterations that have been described in a subset of PF may be seen in gastroblastoma and malignant epithelioid tumor with gliomaassociated oncogene homologue 1(GLI1)rearrangement.The recent increase in publications on PF reflects growing recognition of this entity with expansion of clinical and pathologic findings in these cases.Herein we provide a review of PF in comparison to other mesenchymal tumors with histologic and molecular resemblance to raise the awareness of this enigmatic neoplasm.Also,we highlight the challenges pathologists face when the sample is small,or such rare entity is encountered intraoperatively.

Hepatic Langerhans cell histiocytosis:A review

Hepatic Langerhans cell histiocytosis(LCH)is characterized by proliferation and accumulation of Langerhans cells in the liver,causing liver dysfunction or forming a mass lesion.The liver can be involved in isolation,or be affected along with other organs.A common clinical hepatic presentation is cholestasis with pruritis,fatigue and direct hyperbilirubinemia.In late stages,there may be hypoalbuminemia.Liver biopsy may be required for the diagnosis of hepatic LCH.Histologic finding may be diverse,including lobular Langerhans cell infiltrate with mixed inflammatory background,primary biliary cholangitis-like pattern,sclerosing cholangitis-like pattern,and even cirrhosis at later stages.Because of its non-specific injury patterns with broad differential diagnosis,establishing a diagnosis of hepatic LCH can be challenging.Hepatic LCH can easily be missed unless this diagnosis is considered at the time of biopsy interpretation.A definitive diagnosis relies on positive staining with CD1a and S100 antigen.Liver involvement is a high risk feature in LCH.The overall prognosis of hepatic LCH is poor.Treating at an early stage may improve the outcome.Systemic chemotherapy is the mainstay of treatment and liver transplantation may be offered.New molecular markers involved in pathogenesis of LCH are being explored with a potential for targeted therapy.However,further studies are needed to improve outcome.

Differential diagnosis and management of immune checkpoint inhibitor-induced colitis: A comprehensive review

Immune checkpoint inhibitors(ICIs)are a new class of cancer pharmacotherapy consisting of antibodies that block inhibitory immune regulators such as cytotoxic T lymphocyte antigen 4,programmed cell death 1 and programmed death-ligand 1.Checkpoint blockade by ICIs reactivates a tumor-specific T cell response.Immune-related adverse events can occur in various organs including skin,liver,and gastrointestinal tract.Mild to severe colitis is the most common side effect with some experiencing rapid progression to more serious complications including bowel perforation and even death.Prompt diagnosis and management of ICI-induced colitis is crucial for optimal outcome.Unfortunately,its clinical,endoscopic and histopathologic presentations are non-specific and overlap with those of colitis caused by other etiologies,such as infection,medication,graftversus-host disease and inflammatory bowel disease.Thus,a definitive diagnosis can only be rendered after these other possible etiologies are excluded.Sometimes an extensive clinical,laboratory and radiologic workup is required,making it challenging to arrive at a prompt diagnosis.Most patients experience full resolution of symptoms with corticosteroids and/or infliximab.For ICI-induced colitis that is treatment-refractory,small scale studies offer alternative strategies,such as vedolizumab and fecal microbiota transplantation.In this review,we focus on the clinical features,differential diagnosis,and management of ICIinduced colitis with special attention to emerging treatment options for treatmentrefractory ICI-induced colitis.