Abstract
BackgroundPseudomyogenic hemangioendothelioma (PHE) is an unusual vascular tumor of intermediate malignancy that rarely metastasizes and tends to arise in the lower limbs of young adults and children. Histologically, PHE shows fascicular proliferation of eosinophilic spindle cells and/or epithelioid cells showing “pseudomyogenic” morphology. Immunohistochemically, PHE is usually positive for vimentin, cytokeratin, CD31 and ERG.MethodWe examined FOSB immunohistochemistry (IHC) in 27 cases consisting of 4 PHE and its histologic mimics including 6 epithelioid hemangioendotheliomas (EHE), 8 angiosarcomas (AS), 4 Kaposi sarcomas (KS) and 5 epithelioid sarcomas (ES). In addition, we performed IHC of CAMTA1 which has recently been established as a useful marker of EHE. We elucidated the diagnostic utility of FOSB IHC in the differential diagnosis of PHE and its histological mimics and also examined the usefulness of FOSB and CAMTA1 IHC combination in the differential diagnosis of the tumors.ResultsIHC revealed diffuse and strong FOSB expression in all PHE cases, while the other tumor types demonstrated limited, weak or no FOSB expression. All EHE cases exhibited diffuse and moderate to strong expression of CAMTA1. All tumor types except for EHE showed limited, weak or no CAMTA1 reactivity.ConclusionsDiffuse and strong FOSB expression was specific for PHE in the current series and FOSB IHC is an effective tool for differentiating between PHE and its histological mimics. Moreover, the combination of FOSB and CAMTA1 IHC is useful for distinguishing PHE from EHE.
Highlights
Pseudomyogenic hemangioendothelioma (PHE) is an unusual vascular tumor of intermediate malignancy that rarely metastasizes and tends to arise in the lower limbs of young adults and children
Diffuse and strong FOSB expression was specific for PHE in the current series and FOSB IHC is an effective tool for differentiating between PHE and its histological mimics
The combination of FOSB and CAMTA1 IHC is useful for distinguishing PHE from epithelioid hemangioendothelioma (EHE)
Summary
Pseudomyogenic hemangioendothelioma (PHE) is an unusual vascular tumor of intermediate malignancy that rarely metastasizes and tends to arise in the lower limbs of young adults and children. PHE tends to arise in the lower limbs, Sugita et al Diagnostic Pathology (2016) 11:75 They described this peculiar vascular tumor as a variant of hemangoendothelioma, showing solid sheet and nest proliferation of round to slightly spindle cells with prominent eosinophilic cytoplasm. EHE is the most important tumor in the differential diagnosis of PHE, because its histological findings and clinical presentation are similar to those of PHE. Both of them usually show a fascicular proliferation of relatively bland spindle and/or epithelioid cells with eosinophilic cytoplasm. PHE tends to emerge with multiple musculoskeletal lesions, often involving skeletal bones [3] and EHE has a tendency to form multifocal lesions in the bone
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