title: Diagnostic utility of FOSB immunohistochemistry in pseudomyogenic hemangioendothelioma and its histological mimics.
abstract: BACKGROUND
  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. 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.
  
  
  METHODS
  We 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.
  
  
  RESULTS
  IHC 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.
  
  
  CONCLUSIONS
  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. Moreover, the combination of FOSB and CAMTA1 IHC is useful for distinguishing PHE from EHE.
authors: Department of Surgical Pathology, Sapporo Medical University, School of Medicine, South 1, West 16, Chuo-ku, Sapporo, Hokkaido, 060-8543, Japan.
authors: Shintaro
authors: S
authors: Sugita
authors: Department of Surgical Pathology, Sapporo Medical University, School of Medicine, South 1, West 16, Chuo-ku, Sapporo, Hokkaido, 060-8543, Japan.
authors: Hiroshi
authors: H
authors: Hirano
authors: Department of Surgical Pathology, Sapporo Medical University, School of Medicine, South 1, West 16, Chuo-ku, Sapporo, Hokkaido, 060-8543, Japan.
authors: Noriaki
authors: N
authors: Kikuchi
authors: Department of Surgical Pathology, Sapporo Medical University, School of Medicine, South 1, West 16, Chuo-ku, Sapporo, Hokkaido, 060-8543, Japan.
authors: Terufumi
authors: T
authors: Kubo
authors: Department of Surgical Pathology, Sapporo Medical University, School of Medicine, South 1, West 16, Chuo-ku, Sapporo, Hokkaido, 060-8543, Japan.
authors: Hiroko
authors: H
authors: Asanuma
authors: Department of Surgical Pathology, Sapporo Medical University, School of Medicine, South 1, West 16, Chuo-ku, Sapporo, Hokkaido, 060-8543, Japan.
authors: Tomoyuki
authors: T
authors: Aoyama
authors: Department of Orthopedic Surgery, Sapporo Medical University, School of Medicine, South 1, West 16, Chuo-ku, Sapporo, Hokkaido, 060-8543, Japan.
authors: Makoto
authors: M
authors: Emori
authors: Department of Surgical Pathology, Sapporo Medical University, School of Medicine, South 1, West 16, Chuo-ku, Sapporo, Hokkaido, 060-8543, Japan. hasetada@sapmed.ac.jp.
authors: Tadashi
authors: T
authors: Hasegawa
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D014408:Biomarkers, Tumor / Q000032:analysis*; D002135:Calcium-Binding Proteins / Q000032:analysis; D003937:Diagnosis, Differential; D005260:Female; D006390:Hemangioendothelioma / Q000737:chemistry* / Q000145:classification / Q000473:pathology; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D016760:Proto-Oncogene Proteins c-fos / Q000032:analysis*; D012983:Soft Tissue Neoplasms / Q000737:chemistry* / Q000145:classification / Q000473:pathology; D015534:Trans-Activators / Q000032:analysis; D055815:Young Adult
chemical_list: D014408:Biomarkers, Tumor; C487554:CAMTA1 protein, human; D002135:Calcium-Binding Proteins; C064269:FOSB protein, human; D016760:Proto-Oncogene Proteins c-fos; D015534:Trans-Activators
keywords: Angiosarcoma; CAMTA1; Epithelioid hemangioendothelioma; Epithelioid sarcoma; FOSB; Immunohistochemistry; Kaposi sarcoma; Pseudomyogenic hemangioendothelioma