A case of multiple lung carcinoid tumors localized in the right lower lobe

Typical pulmonary carcinoid (TC) tumors are low-grade neuroendocrine tumors and usually detected as indolent solitary tumors. We herein report a case of multiple pulmonary carcinoid tumors and tumorlets localized in the right lower lobe with no underlying lung disorders suggesting diffuse idiopathic pulmonary neuroendocrine cell hyperplasia (DIPNECH). A 28-year-old man with multiple 1-to-8-mm pulmonary nodules in the peripheral pulmonary parenchyma of the right lower lobe was referred to our hospital. The patient underwent a surgical biopsy. Pathological examination revealed multiple nodules composed of spindle cells, and immunohistochemistry revealed staining for chromogranin A, synaptophysin, and CD56, suggesting neuroendocrine tumors. He was diagnosed as having multiple TC tumors and tumorlets. Neuroendocrine cell hyperplasia (NECH) was also observed on some bronchioles. A follow-up CT scan after 6 months showed no changes in the sizes of the nodules and no new lesions. The present case was histopathologically compatible with DIPNECH but it occurs mainly in elderly women. The patient might be in an early stage of DIPNECH before progression to symptomatic DIPNECH. In conclusion, clinicians should consider the possibility of carcinoid tumors and tumorlets in cases with multiple pulmonary nodules even if they are localized in one lobe.