Primary and metastatic lesions from a fibroxanthosarcoma (FXS) originating in the neck of a 29‐year‐old Caucasian woman are reported. Light and electron microscopic observations are correlated to define the various types of cells constituting this neoplasm. Ultrastructural examination verified that several types of cells can act as facultative fibroblasts. Since a malignant potentiality cannot be predicted solely from the histopathology of fibroxanthomas, an attempt was made to categorize certain ultrastructural nuclear and cytoplasmic organelles associated with FXS cells. This was done in order to further define the malignant neoplastic cells of the FXS, so that distinguishing the malignant from benign forms of this neoplasm may become more feasible.

A rare malignant blue nevus resected from the back of a 34‐year‐old Caucasian woman is reported. Histopathologic examination showed the presence of a CBN as well as MBN. The CBN elements of this lesion showed the characteristic prominent neural type fascicles intertwined with melanocytes. The deeper regions of this skin neoplasm showed considerable variation in histopathologic patterns. Metastascs to the axillary lymph nodes and multiple subdermal soft tissue sites, invasion of the underlying skeletal muscle, and several recurrences in the chest wall indicate that this neoplasm is malignant, though of a lower order than a malignant melanoma. The ultrastructural characteristics of neoplastic cells indicate that this neoplasm is of Schwann cell origin.

Control mice and those treated with cortisone were exposed to aerosols of viable spores of Aspergillus flavus. Fifteen to 20 minutes later, animals were killed, and alveolar macrophages were obtained by tracheobronchial lavage. Electron-microscopic examination of these cells revealed that, whereas the lysosomes of control macrophages showed extensive attraction and fusion with the phagocytic membranes surrounding spores, the lysosomes of macrophages from animals treated with cortisone revealed little, if any, interaction. This diminished lysosomal response in forming phagocytic vacuoles may be important in the subsequent development of hyphal bronchopneumonia which frequently, occurs in cortisonetreated mice exposed to spores of A. flavus.

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