Fig. 1

Histopathology and immunohistochemistry analysis of the primary neoplastic tissue. Sections of lung stained with hematoxylin and eosin (H&E) with a well-demarcated region of neoplastic cells replacing the normal pulmonary parenchyma. Neoplastic cells presented as a highly pleomorphic population of malignant histiocytic cells with marked anisocytosis and anisokaryosis. The cells contained large amounts of basophilic and typically mildly vacuolated cytoplasm. Multinucleation, megalocytosis and megalokaryosis were common features. One to several prominent nucleoli were present in most nuclei. Perimembranous expression of CD18 was strongly detected by immunohistochemistry