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Edited by: Philippe Chanson, Université Paris-Sud, France

Reviewed by: Giovanni Vitale, Universitá Degli Studi di Milano, Italy; Arantzazu Sebastian-Ochoa, Virgen de la Victoria Hospital, Spain

*Correspondence: Antongiulio Faggiano, Istituto di Ricovero e Cura a Carattere Scientifico Fondazione SDN, 80131 Napoli, Italy. e-mail:

This article was submitted to Frontiers in Cancer Endocrinology, a specialty of Frontiers in Endocrinology.

This is an open-access article subject to a non-exclusive license between the authors and Frontiers Media SA, which permits use, distribution and reproduction in other forums, provided the original authors and source are credited and other Frontiers conditions are complied with.

Bronchopulmonary carcinoids are no more than 2% of lung primary tumors (Hurt and Bates,

The mitotic index (number of mitosis for 10 high-power fields) is one of the criteria used for the differential diagnosis between typical and atypical forms, but given the considerable inter-operators variability, the expression of Ki-67 was tested as a potentially more accurate tool for the assessment of tumor proliferative activity. Ki-67 is a nuclear antigen expressed by proliferating cells. In bronchopulmonary carcinoids Ki-67 score has been reported to be around 0.2–1.1% in TC and 0 .3–20.3% in AC. Several studies reported an association between high Ki-67 expression and a worse prognosis (el-Naggar et al.,

One hundred thirty consecutive cases of bronchopulmonary carcinoid treated at the University Hospitals of Udine (from 1990 to 2010) and at the Cardarelli Hospital of Naples (from 2000 to 2010) were histologically reviewed and independently assessed by two expert pathologists. Tumors treated with laser therapy (13 cases, 12 typical and 1 atypical carcinoid) or surgery without an adequate sampling of regional lymph nodes (10 cases, all typical carcinoid) were excluded. A further case was excluded because at histology it was consistent with multiple lesions less than 2 mm in diameter, thus having to be ascribed to the category of “tumorlets.” The patients finally included in the study were 106, all treated with radical surgical excision (confirmed by histological sections), and adequate sampling of the ilo-mediastinal lymph nodes (sampling lymphadenectomy). No patient underwent adjuvant therapy except in cases of disease relapse.

Tumor stage was established on the basis of the last TNM classification of lung tumors. The gross features of the tumor were derived from the original macroscopic report. The histological features of the tumor were obtained by new sections of the paraffin-embedded samples; these sections were then stained with hematoxylin and eosin and analyzed by two expert pathologists (Carlo Alberto Beltrami, Stefano Pizzolitto; not familiar with the original diagnosis or the details of the patient) who reviewed the whole series on the basis of the recent seventh WHO classification of lung tumors (Travis et al.,

The main outcome considered in this study was disease-free survival defined as a period of time (in years) elapsed between surgery and recurrence. First of all, we performed the univariate analysis of every prognostic factor using the Mann–Whitney, Fisher exact, and Spearman’s rho tests to determine statistical significance of correlation. To identify independent variables associated with outcome we used the multivariate Cox regression model. The analysis of ROC curves (Receiver Operating Characteristics) allowed us to identify the best cut-off of Ki-67 nuclear expression to stratify the patients according to the clinical outcome (relapse vs no relapse). The probability of disease-free survival was evaluated by the Kaplan–Meier curves stratifying patients according to the prognostic factors. The statistical significance of the difference between curves was evaluated by log-rank test.

Among the 106 patients included in the study the male/female ratio was 45/61 without a statistically significant difference between the group of TC and that of AC (30/45 and 15/16, respectively). The average age was 55.1 ± 14.9 years (range 21–82, median 57) without any significant difference between TC (average 53.3 ± 14.9; median 55.0) and AC (mean 59.4 ± 14.1; median 63.0). The mean follow-up was 8.3 ± 5.3 years with a range from 0 to 20 years and a median of 8 years. Recurrence occurred in 29 patients (27.4%), 14 of whom had a TC and 15 an AC, with a mean disease-free survival of 7.3 ± 5.2 years (8.5 ± 5.1 years among the patients with TC and 4.2 ± 4.2 years among those with AC). Twenty-two patients (20.8%) died during the follow-up, 11 of them because of recurrence/progression of disease (Table

All 106 | TC 75 (70.8%) | AC 31 (29.2%) | ||
---|---|---|---|---|

Sex (male) | 45 (42.5%) | 30 (40%) | 15 (48.4%) | |

Age (years) | 55.1 ± 14.9 | 53.3 ± 14.9 | 59.4 ± 14.1 | |

Size (cm) | 2.6 ± 1.4 | 2.3 ± 1.4 | 3.2 ± 1.4 | |

Central Location (%) | 55 (51.9%) | 41 (54.7%) | 14 (45.2%) | |

Mitosis upon 10 HPF | 1.4 ± 1.8 | 0.6 ± 0.9 | 3.4 ± 2.0 | |

Presence of necrosis (%) | 18 (17.0%) | 0 | 18 (58.1%) | |

Nodal metastasis (%) | 21 (19.8%) | 12 (16.0%) | 9 (29.0%) | |

pN1 (%) | 14 (13.2%) | 9 (12.0%) | 5 (16.1%) | |

pN2 (%) | 7 (6.6%) | 3 (4.0%) | 4 (12.9%) | |

Ki-67 (%) | 5.0 ± 10.0 | 2.9 ± 3.2 | 9.5 ± 16.6 | |

Recurrence (%) | 29 (27.4%) | 14 (18.7%) | 15 (48.4%) | |

DFS (years) | 7.3 ± 5.2 | 8.5 ± 5.1 | 4.2 ± 4.2 | |

Death (%) | 22 (20.8%) | 9 (12.0%) | 13 (41.9%) | |

Tumor related death (%) | 11 (10.4%) | 0 | 11 (35.5%) | |

OS (years) | 8.3 ± 5.2 | 9.4 ± 5.1 | 5.8 ± 4.6 |

The tumor size ranged from a minimum of 1 cm to a maximum of 10.0 cm with an average of 2.6 ± 1.4 cm and a median of 2.2 cm. In 55 cases (51.9%) the tumor was centrally located (main, lobar, or segmental bronchus), while in 51 cases (48.1%) it was peripherally located. The exact location of tumors within the lungs is shown in Figure

Original diagnosis | Revision | |
---|---|---|

TC | AC | |

“Neuroendocrine tumor” | 3 | 4 |

TC | / | 2 |

AC | 6 | / |

Total | 9 (60.0%) | 6 (40.0%) |

Nodal metastasis (%) | 0 | 1 (6.7%) |

Relapse (%) | 0 | 4 (26.7%) |

Overall mitotic index was found to be an average of 1.4 ± 1.8 mitosis with a statistically significant difference (Mann–Whitney

At univariate analysis, the recurrence of disease was significantly correlated to histotype (Fisher test

Univariate analysis. Correlation between recurrence and: | Multivariate analysis (Cox regression model) | |||
---|---|---|---|---|

Risk ratio | 95% CI | |||

Age | / | / | / | |

Sex | / | / | / | |

Size | 1.0 | 0.9–1.1 | 0.502 | |

Histotype (TC vs AC) | 3.4 | 1.1–10.7 | 0.061 | |

Mitotic index | 0.9 | 0.7–1.3 | 0.585 | |

Nodal metastasis | 2.3 | 0.8–6.6 | 0.110 | |

N stage | 0.9 | 0.2–3.1 | 0.822 | |

pTNM stage | / | / | / | |

Ki-67 | 20.5 | 2.1–201.3 | 0.009 | |

Ki-67 > 0.04 | / | / | / |

All possible prognostic factors identified by univariate analysis were tested at the multivariate analysis according to Cox regression model which showed that the best independent variable being able to predict recurrence of disease was Ki-67 score (risk ratio 20.5; 95% CI: 2.1–201.3%;

According to the recent classification of lung tumors developed by the World Health Organization (Travis et al.,

The ratio between central and peripheral forms (55:51) is instead consistent with data reported in the literature (Soga and Yakuwa,

The univariate analysis identified factors that are related with the risk of relapse (histological diagnosis, mitotic index, lymph node metastases, size of primary tumor, TNM stage, and expression of Ki-67), but their prognostic potential disappeared when the expression of Ki-67 was added in Cox’s multivariate regression model. The relationship between tumor proliferative activity and outcome is a given, but there are still doubts as to what is the best method to determine the proliferative activity of tumor, what is the most appropriate cut-off in predicting the outcome and whether the proliferative rate constitutes an independent variable in predicting the outcome.

Travis et al. (

In the present study the evaluation of Ki-67 was made by counting the percentage of positive nuclei upon 2000 cells. At the moment the operator counting is the gold standard, however there are increasing evidences about the effectiveness of computerized counting systems that in the future can be used in order to decrease inter-operator variability and analysis time. (Fasanella et al.,

In conclusion this study has shown that the expression of Ki-67 could be an optimal prognostic factor for bronchopulmonary carcinoids, and therefore, Ki-67 score may be a crucial factor to decide the postoperative follow-up strategies.

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

This study was partially supported by a grant from the Italian Minister of Research and University in Rome (no. 2008LFK7J5).