Solitary fibrous tumors are uncommon spindle cell
neoplasms originally thought to be restricted to the pleura. We describe a 62-year-old woman who presented with
stridor and an anterior mediastinal mass. At
thoracotomy, a 10.5 x 6.5 x 5.5 cm, circumscribed, firm mediastinal mass demonstrated no direct cardiac or pulmonary involvement. The
tumor consisted of spindle cells organized in a patternless pattern with collagenous stroma and
hemangiopericytoma-like vessels. Spindle cells were immunoreactive for CD34, CD99,
desmin,
vimentin and bcl-2
protein and a diagnosis of mediastinal
solitary fibrous tumor was confirmed. The differential diagnosis of mediastinal
solitary fibrous tumors is extensive and includes spindle cell
thymoma, sarcomatoid
carcinoma,
malignant mesothelioma, inflammatory myofibroblastic
tumor, peripheral nerve sheath
tumors and various
sarcomas. Despite their rarity in the mediastinum,
solitary fibrous tumors can be recognized by their classic patternless morphology and immunophenotypic pattern. Their accurate classification is important, as
solitary fibrous tumors are intermediate (rarely metastasizing)
neoplasms that require complete surgical excision and long-term clinical follow-up for optimum
therapy.