Papillary endothelial hyperplasia presenting as a chest wall neoplasm.

Soft tissue hematomas generally resolve but may persist and develop into slow-growing, organized masses. These chronic expanding hematomas are characterized by a pseudocapsule and a predominantly necrotic central cavity, with foci of newly formed capillaries. These have been called chronic expanding hematomas or Masson's papillary endothelial hyperplasia. These lesions can mimic vascular neoplasms and must be considered in the evaluation of expanding soft tissue vascular malformations.