Hemangiopericytoma/solitary fibrous tumor of pectoralis major muscle mimicking a breast mass

INTRODUCTIONHemangiopericytoma (HPC)/solitary fibrous tumor (SFT) is a very uncommon tumor of uncertain malignant behavior. In 1942, Stout and Murray first characterized these neoplasms as “vascular tumors arising from Zimmerman's pericytes” and till now hemangiopericytomas and solitary fibrous tumors of the soft tissues are regarded as features of the same entity in the soft tissue fascicle.PRESENTATION OF CASEWe present a case of hemangiopericytoma/solitary fibrous tumor of the pectoralis major muscle in a 33-year-old female. She first noticed a painless mass in her right breast. Ultrasound of the breast revealed a large heterogeneously hypoechoic lesion within the pectoralis major muscle. Fine needle aspiration of the tumor did not produce any meaningful result. The lesion was completely removed by surgical resection. Histologically, the tumor had staghorn-like vasculature and immunohistochemistry for CD34 was positive, whereas desmin, smooth-muscle actin, S-100 protein, cytokeratins (AE1/AE3) and epithelial membrane antigen (EMA) were all negative. A diagnosis of hemangiopericytoma/solitary fibrous tumor was rendered.DISCUSSIONTumors comprising the HPC/SFT spectrum represent a small subset of soft tissue sarcomas and are found virtually at any site in the body. Wide surgical resection can achieve favorable long-term survival.CONCLUSIONDue to the rarity and unpredictable biological potential of these tumors, long-term follow-up is mandatory even after radical resection, because recurrence or development of metastasis may be delayed many years.