Small cell neuroendocrine carcinoma (Thymus)

This is a low power view of a rare tumor which is identical histologically and biologically to small cell carcinoma  of the lung (oat cell carcinoma). Both thymic and lung primaries are rapidly growing tumors which metastasize early in their course. 

The component cells are small and have hyperchromatic nuclei and small amounts of cytoplasm. Some of these  tumors may be associated with the paraneoplastic (ectopic) production of ACTH (adrenocorticotrophic hormone).

From the slide collection of the late Dr. Charles Kuhn; Legend contributed by Dr. Ron DeLellis