Bone marrow metastatic neuroendocrine carcinoma with unknown primary site: A case report and review of the literature

Figure 2 Bone marrow biopsy. A: Hematoxylin and eosin staining showed nest-like distributions of small cells with less cytoplasm, round or irregular nuclei and dark stained chromatin in the stroma (× 400); B: Reticulin staining was positive (+++) (× 400); C and D: Immunohistochemical staining exhibited that the tumor cells were positive for CD56 (C) (× 400) and synaptophysin (D) (× 400).