Thymic Poorly Differentiated Neuroendocrine Carcinoma
Definition
- High grade carcinoma of the thymus demonstrating neuroendocrine differentiation
Diagnostic Criteria
- Due to their rarity, diagnostic criteria are not clearly defined; use of pulmonary criteria is probably appropriate
- Small cell (undifferentiated) carcinoma
- Scant cytoplasm, very high nucleus/cytoplasm ratio
- Finely granular, stippled chromatin
- Nucleoli small to absent
- Nuclear molding
- Immunohistochemical demonstration of neuroendocrine differentiation not required
- Large cell neuroendocrine carcinoma requires both morphologic and immunohistologic (or ultrastructural) evidence of neuroendocrine differentiation
- Morphologic features suggestive of endocrine differentiation (not all are seen in each case)
- Generally uniform polygonal/cuboidal cells
- Nesting and/or broad trabeculae with nuclear palisading
- Rosettes and rosette like structures
- Demonstration of endocrine differentiation is required
- Percent of cells required to stain not defined
- Synaptophysin and chromogranin are the most specific
- Morphologic features suggestive of endocrine differentiation (not all are seen in each case)
- Areas of carcinoid may be seen in both
- Small cell (undifferentiated) carcinoma
Robert V Rouse MD
Department of Pathology
Stanford University School of Medicine
Stanford CA 94305-5342