The chronic
oral administration of nitrosomorpholine (NM) and
nitrosopiperidine (NP) to 360 adult Syrian golden hamsters of both sexes resulted in the induction of a high incidence of laryngo-tracheal
tumors, which in the group treated with 0.01%
solution of NM affected up to 80% of the males. A total of 232 different laryngo-tracheal
tumors were found. 36 of these were located within the supraglottic and glottic larynx, 62 were within the subglottic and glottic larynx, and 134 arose within the trachea. Among the laryngeal supraglottic and glottic
tumors there were 18
squamous cell carcinomas, 16
squamous cell papillomas and only 2 mixed cell mucoepidermoid
papillomas. All the subglottic laryngeal
tumors and tracheal
tumors were mixed cell mucoepidermoid
papillomas. In this study, the
squamous cell carcinomas observed within the larynx of hamsters bear morphological and
biological similarities to their
tumor counterpart found in the larynx of adult man. The laryngeal squamous
papillomas observed in this experiment are not similar to the squamous
papillomas occurring in man during infancy and childhood. The mixed cell mucoepidermoid
papillomas of the hamster trachea and subglottis are a peculiar
neoplasm of this species, which morphologically and biologically differs from the cases of tracheal
papillomatosis described in man, as well as from the
mucoepidermoid tumors of major and minor salivary gland origin also seen in this latter species.