Microscopic Description -- Anterior Mediastinal Mass


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 focal 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 extends 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.



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