PMC4681625_01
Needle biopsy of the mediastinal mass. A. The hypercellular tumor consists of sheets of small poorly differentiated cells with scanty cytoplasm and round to ovoid, finely granular nuclei containing inconspicuous nuclei. Karyorrhectic debris is evident in the left side of the field. Other fields showed frequent mitoses. (Hematoxylin and eosin stain; 200x). Immunohistochemical evaluation of the tumor cells showed positive staining with B. cytokeratins (here AE1/AE3; 200x), and with C. neuroendocrine markers (here neuron-specific enolase; 200x).
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F1
CT guided biopsy of the mediastinal mass revealed a poorly differentiated small round blue cell tumor (Figure 1A). However, epithelial (CK7, EMA) and neuroendocrine (NSE, CD56, chromogranin, synaptophysin) markers were positive, supporting a diagnosis of poorly differentiated neuroendocrine small cell carcinoma (Figure 1B and C).