Clinicopathological indicators of survival among patients with pulmonary carcinoid tumor

Pulmonary carcinoids (PC) are rare malignant neoplasms that cover approximately 1% of all lung cancers. PCs are classified by histological criteria as either typical (TC) or atypical (AC). Histological subtype is the most studied prognostic factor. The aim of this study was to evaluate if other tissue or clinical features are associated with patient outcomes.

We retrospectively reviewed clinical records of 133 PC patients who underwent operation in the Helsinki University Hospital between 1990 and 2013. Tissue specimens were re-evaluated, processed into tissue microarray format and stained immunohistochemically with serotonin, calcitonin, adrenocorticotropic hormone (ACTH), thyroid transcription factor-1 (TTF-1) and Ki-67. Survival and risk analyses were performed.

Based on histology, 75% (n = 100) of the tumors were TCs and 25% (n = 33) ACs. TCs had higher 10-year disease-specific survival (DSS) rate than ACs (99% (95% CI, 93-100%) for TCs vs. 82% (95% CI, 61-92%) for ACs). Hormonally active tumors expressing serotonin, calcitonin or ACTH were noted in 53% of the specimens but hormonal expression was not associated with DSS. TTF-1 was positive in 78% of the specimens but was not associated with DSS. Ki-67 index varied between <1% and 15%. Ki-67 ≥ 2.5% was associated with shorter DSS (p = .004). The presence of metastatic disease (p = .001), tumor size ≥30 mm (p = .021) and atypical histology (p = .011) were also associated with disease-specific mortality.

We conclude that PCs are uncommon tumors. When resected, the long-term survival is in general favorable. In this consecutive, single-institution cohort of patients, presence of metastatic disease, tumor size, histological subtype and Ki-67 index were associated with shorter disease-specific survival. As TC and AC have different clinical behaviors, the correct tumor classification at the time of diagnosis is a necessity.