BACKGROUND: Although pulmonary carcinoid tumors are generally considered to represent a low-grade malignancy, atypical carcinoids are more aggressive than typical carcinoids, metastasizing more commonly to both regional lymph nodes and distant sites. The treatment of choice for localized disease is surgery. In cases of advanced or metastatic disease, medical treatments, including chemotherapy, have not been proven to be very successful. Therefore, providing careful follow-up is extremely important. In general, tumor markers, such as the level of CYFLA21-1, are often useful for monitoring lung cancer. However, there are currently no sensitive tumor markers for carcinoid tumors. We herein report a rare case of an atypical carcinoid of the lung with the elevation of the serum ProGRP level.

CASE REPORT: A 67-year-old female was referred to our hospital for an abnormal chest X-ray. CT revealed an 18×13 mm nodule in the right middle lobe with no significant mediastinal lymphadenopathy. The serum tumor marker, the ProGRP level, was significantly elevated (161 ng/ml). We performed a right middle lobectomy, because the pathological diagnosis of lung cancer was confirmed according to the results of a rapid frozen section biopsy of the lesion, although the pathological type could not be precisely determined by the frozen section alone. The final pathological diagnosis was atypical carcinoid. The level of ProGRP decreased (69 ng/ml) within 1 month after the surgery.

CONCLUSIONS: The ProGRP level may be useful for monitoring carcinoid tumors, although no serum tumor markers are highly specific or sensitive for detecting recurrences and/or distant metastasis of pulmonary carcinoid tumors. In conclusion, ProGRP should be further evaluated as biomarker in a larger series of patients to determine whether it demonstrates any significant correlation with cancer recurrence.

Keywords: Biopsy, Carcinoid Tumor - surgery, Follow-Up Studies, Lung Neoplasms - surgery, Peptide Fragments - blood, Pneumonectomy, Recombinant Proteins - blood, Tomography, X-Ray Computed, Tumor Markers, Biological - blood