Fig. 4

Histopathologic findings. Atypical cell nests with large nuclei are seen with lung invasion (a). Tumor cells form nests showing a palisading or organoid pattern (b). Cells with bizarre or multiple nuclei are also seen (c). Immunohistochemistry shows positive staining for CD56 (d), chromogranin A (e), synaptophysin (f), and TTF-1 and negative staining for CD5 and p40. The pathologic diagnosis is large cell neuroendocrine carcinoma of the thymus