Typical and atypical carcinoid tumors of lung: two distinct clinicomorphologic entities

Thirty-six cases of bronchopulmonary carcinoid tumor were reviewed in order to identify the clinicomorphologic criteria whereby typical and atypical carcinoids can be classified as two distinct entities. This study indicates that bronchial typical carcinoids are tumors with very low malignancy, more often centrally located and occurring in relatively young patients. The prognosis is good, with a five year-survival rate of about 73%, although regional nodal metastases may occasionally develop. Atypical carcinoids are more frequently peripheral tumors, occurring in comparatively old patients and differing from typical carcinoids by a less favourable prognosis, with a five year-survival rate of about 25% and a higher incidence of nodal metastases. The morphological study of these tumors reveals the following criteria as most reliable for distinguishing between the two types of bronchial carcinoid: increased mitotic activity, cellular pleomorphism and tumor necrosis, which are best correlated with the agressiveness of atypical carcinoids.