The specimen is labeled as"mediastinal mass"and consists of a 16.0 x 10.0 x 5.0 cm portion of soft tissue with an attached 2.0 x 1.0 x 1.0 cm portion of lung closed by staples. Upon sectioning, there is an 11.0 x 7.2 x 3.0 cm well-circumscribed, yellow-tan, mass with an apparent pseudocapsule. This mass is actually separated into three discrete tan, firm, focally hemorrhagic and calcified lobules, up to 8.5 cm in greatest dimension, separated by connective tissue and a small amount of fat. There are also occasional cystic spaces up to 0.2 cm containing serous fluid. Also receive was a portion of the enlarged ectopic parathyroid gland.
Sections demonstrate an inflitrating tumor composed of lobules of round blue cells separated by bands of fibrous connective tissue. Cytologically, the cells demonstrate a "salt and pepper" nucleus, with a relatively dispersed chromatin pattern and inconspicuous nucleoli. Some cells also demonstrate nuclear folds and grooves. The cells have a moderate amount of homogeneous eosinophilic cytoplasm and distinct cell borders. Mitotic figures are not prominent and necrosis is not a feature. The tumor shows vascular invasion and is extending outside of the capsule into the surrounding soft tissue.
Immunoperoxidase stains for cytokeratin (AE1/AE3), neuron-specific enolase (NSE) and synaptophysin are positive. Stains for chromogranin and adrenal corticotropic hormone (ACTH) are negative.