Primary pseudomyogenic hemangioendothelioma of right maxilla: a case with immunohistochemistry and FOSB rearrangement study

Objective Primary pseudomyogenic hemangioendothelioma (PMH) of bone is an extremely rare vascular neoplasm. We present here a case of primary PMH occurring in the maxilla. Study Design A 34-year-old man was referred to our hospital for treatment because of possible recurrence after surgery and chemotherapy of a right maxillary malignant tumor. Morphologic features, immunophenotypes, and FOSB gene rearrangement status of the surgically sectioned sample were assessed by hematoxylin-eosin staining, immunohistochemistry, and fluorescence in situ hybridization, respectively. Results Morphologically, the tumor cells were arranged in a loose fascicular and sheet-like manner, with a large number of reactive woven bones forming. The most striking feature was the presence of epithelioid cells with abundant brightly eosinophilic cytoplasm, which resembled the rhabdomyoblast in appearance. The tumor was diffusely positive for AE1/AE3, CD31, erythroblast transformation-specific transcription factor, and Friend leukemia integration 1; negative for CD34, CAM5.2, epithelial membrane antigen, and desmin; and had retained expression of integrase interactor 1. The tumor harbored FOSB rearrangement. No distant metastasis was found during the follow-up period (18 months). Conclusions To the best of our knowledge, this case represents the first report of PMH arising in the maxilla. The distinct morphologic features, immunophenotypes, and FOSB rearrangement could help achieve precise diagnosis and prevent misdiagnosis of mimics with overlapping features. Primary pseudomyogenic hemangioendothelioma (PMH) of bone is an extremely rare vascular neoplasm. We present here a case of primary PMH occurring in the maxilla. A 34-year-old man was referred to our hospital for treatment because of possible recurrence after surgery and chemotherapy of a right maxillary malignant tumor. Morphologic features, immunophenotypes, and FOSB gene rearrangement status of the surgically sectioned sample were assessed by hematoxylin-eosin staining, immunohistochemistry, and fluorescence in situ hybridization, respectively. Morphologically, the tumor cells were arranged in a loose fascicular and sheet-like manner, with a large number of reactive woven bones forming. The most striking feature was the presence of epithelioid cells with abundant brightly eosinophilic cytoplasm, which resembled the rhabdomyoblast in appearance. The tumor was diffusely positive for AE1/AE3, CD31, erythroblast transformation-specific transcription factor, and Friend leukemia integration 1; negative for CD34, CAM5.2, epithelial membrane antigen, and desmin; and had retained expression of integrase interactor 1. The tumor harbored FOSB rearrangement. No distant metastasis was found during the follow-up period (18 months). To the best of our knowledge, this case represents the first report of PMH arising in the maxilla. The distinct morphologic features, immunophenotypes, and FOSB rearrangement could help achieve precise diagnosis and prevent misdiagnosis of mimics with overlapping features.