It has been emphasized recently by many authors the importance of retention the inhaled dusts to the carcinogenesis of pulmonary carcinoma.This experiment carriedout to observe the effect of carcinogenic activity of Benzo (a) pyrene with mixed dusts (Alumina, Silica) as well as the localisation patterns of tritium labelled Benzopyrene and the dusts in lung. Syrian golden hamsters were given 10 intratracheal injections of the mixed dusts suspended in 0.2ml saline and divided into 4 groups according to the experimental design as follows: 1.BP alone 2.BP with 20 mg of Alumina and 2 mg of Silica 3.Alumina alone 4.untreated control.
Of 15 hamsters is group 1 surviving 450 experimental days, 33.3% developed a lung cancer, while the group 2 given the same carcinogen with mixed dusts developed lung cancers with a larger rate of occurrence. These cancers were much more adenocarcinomas originating from terminal bronchi where persist the considerable amount of the dusts as well as the silver grains in microautoradiographic study by 3, 4. BP. There were also some squamous carcinomas originating from metaplastic foci of large bronchi.No tumorous change was observed in group 3 and none treatedcontrol.
The author suggess that the prolonged contact between the mixed dust which might to adsorb BP and the tissue seems to arise the cancerous change in the epithelium of the respiratory tract.
In this point of view, the author discussed the role of scar tissue in the lung carcinogenesis, adding the some results of experimental scar cancer.

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Thirty-three histologically proven cases of oat-cell carcinoma were examined to find morphological characteristics of the exfoliated tumor cells in sputum and in specimens obtained by bronchoscopy and by the TV-burshing method.
Sputum cytology proved in 77.4%, cytology of specimens obtained by bronchos copy and by the TV-brushing method proved in 85.1% and 100%, respectively.
Tumor cells were usually small, but occasionally larger than 11 microns in diameter. Large tumor cells were observed more in cases of a central type tumor than in cases of a peripheral type tumor. The nuclei were usually round, polygonal, orirregular.
Tumor cells with the light stained nuclei were often mixed with those with the dark stained nuclei in the same smear.Many finely granular chromatin and a few coarsely granular or coarsely reticular chromatin were seen in the light stained nuclei and coarsely granular or coarsely reticular chromatin were rather numerously seen in the dark stained nuclei.It is suggested that the light stained nuclei quickly degenerated from finely granular chromatin to india-ink spots while the dark stained nuclei slowly degenerated to coarse chromatin and remained in that state.Chromatin of fresh cancer cells obtained by bronchoscopy or by the TV-brushing method was mostly finely reticular or granular, but occasionally coarsely reticular or granular. As coarsely reticular or granular chromatin was considered to belong to degenerative nuclei, it is suggested that even in living cancer tissue, some degenerative changes of cancer cells were in progress.
A cytological comparison was made of oat cell carcinoma, bronchial carcinoid and neuroblastoma on their imprinted smear following resection or autopsy. It was assumed that these tumors might have a similar origin because of their morphological likeness.

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Characteristics of clinical and radiological findings of primary lung cancer with cavity were studied on 23 cases admitted to our clinic in the past 10 years.
Incidence was higher in the fifth and sixth decades and more common in male than female (2.3:1). Histological types of these 23 cases were squamous cell carcinoma (15 cases), adenocarcinoma (5 cases) and undifferentiated carcinoma (3 cases).
The mechanism of cavity formation seemed to be different among these histological types of lung cancer.The size of cavity was over 4cm in diameter in 10 out of 15 cases of squamous cell carcinoma and one half of the cases had distinct clinical and laboratorical evidences of concomitant infection. Contrarily, no such inflammatory findings were seen in the other 5 cases of squamous cell carcinoma where tumor was under 4cm in diameter.All of the 3 cases of undifferentiated carcinoma (tumor was over 8 cm in 2 cases and 4cm in 1 case in diameter) showed definite evidence of inflammation.These findings indicated a possible mechanism of cavity formation in these two histological types of lung cancer, that necrosis would occur in consequence of ischemic changes which would appear when the size of tumor became larger than 4cm in diameter, and in addition to this, infection of the part would accelerate the formation of the cavity.
On the other hand, the cavity was observed in all cases of adenocarcinoma in spite of the size of tumor being about 4cm in diameter or less: From these histological findings, it was thought that the main factor of cavity formation in this type of lung cancer would be the ischemic necrosis in the tumor.

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