A case of salivary gland-type mixed tumor of the lung differentiating toward type II alveolar epithelial cells in glandular components with a literature review.

Salivary gland-type mixed tumor primarily arising in the lung is extremely rare. We report here a case of this type of tumor that occurred in the periphery of S4 of the right middle lobe in a 74-year-old man. Light-microscopically, this lung tumor, 15x9mm in size, exhibited almost the same features as those of mixed tumor of the salivary gland intermingled with chondromyxoid stroma, glandular component, solid growth pattern of myoepithelial components and well-developed cartilage formation, exhibiting a sharp margin. Immunohistochemical study revealed that the glandular components in the tumor was positive for thyroid transcription factor-1, TTF-1, a marker of epithelial cells of the thyroid as well as the lung. Furthermore, surface lining cells of the glandular components and luminal contents were positive for surfactant apoprotein A, PE-10, used as a marker of type II alveolar epithelial cells. These findings clearly demonstrate for the first time that glandular epithelial cells in the present salivary gland-type mixed tumor exhibited differentiation toward type II alveolar epithelial cells.

[A case of pulmonary actinomycosis with a unique finding in the chest MR image].

A 57-year old man, who was complaining of a productive cough and right shoulder pain, was admitted to our hospital because of an irregularly shaped mass located at rt. S1 on a chest radiograph. Bronchoscopy revealed no evidence suggesting lung cancer or any specific infection, either pathologically or microbiologically. CT-guided biopsy revealed changes resembling lymphocytic or plasmocytic interstitial pneumonitis with thickening of the alveolar septum and with accumulations of mononuclear cells and plasma cells, indicating the proliferation of bronchus-associated lymphoid tissue (BALT system). Since no definitive diagnosis was considered possible, a right upper lobectomy was performed. Histopathologic examination of tissue from the right upper lobe revealed sulfur granules and branching Gram-positive filamentous bacteria, and the condition was pathologically diagnosed as pulmonary actinomycosis. In the center of the mass lesion, the patient's chest MRI showed a very small area with a low signal intensity in T1- and a high signal in T2-weighted images, which suggested an accumulation of fluid in the actinomycotic abscess. As detailed MR findings in this condition have not been well described in the literature, the MRI evidence seen in this case may be useful for the diagnosis of actinomycosis.

Ultrastructural study of nuclear inclusions immunohistochemically positive for surfactant protein A in pulmonary adenocarcinoma with special reference to their morphogenesis.

To investigate the fine-structural nature of nuclear inclusions immunopositive for surfactant protein A (SP-A) antibody staining, a detailed ultrastructural study was performed, as well as immunohistochemical examination of pulmonary adenocarcinomas. Surgically resected tumor specimens from 31 patients were examined by immunohistochemistry focused on reactivity to SP-A and thyroid transcription factor 1 (TTF-1) antibodies. Only cases with >5% positive nuclear inclusions in cancer cells were considered positive, some of which were examined by electron microscopy. Immunohistochemically, 6 of 31 cases were doubly positive for SP-A and TTF-1 antibodies. On electron microscopy, SP-A-positive nuclei contained diffuse or globular fine granular substance as inclusions. Both types of globular and diffuse inclusions were sometimes connected to the inner nuclear membrane, in association with fragmented or stacked membranous structures. The findings of this study suggested that nuclear inclusions positive for SP-A antibody staining in adenocarcinomas of the lung were derived from accumulated content in the perinuclear cistern resembling pseudoinclusion processes and composed of proteins antigenically cross-reactive with SP-A.