Metastatic Neuroendocrine Tumor: Given the patient's history of a neuroendocrine tumor, the lung nodule could represent a metastasis from the primary tumor. Neuroendocrine tumors have a propensity to metastasize to the lungs, among other sites.

Primary Lung Cancer: The presence of a lung nodule in a patient with a history of neuroendocrine tumor does not exclude the possibility of a primary lung malignancy, especially if the patient has risk factors such as smoking.
Benign Lung Nodule: Not all lung nodules are malignant. The nodule could be a benign lesion such as a hamartoma, granuloma, or an infectious process.
Carcinoid Tumor: If the neuroendocrine tumor was a carcinoid, there's a possibility that the lung nodule could be a primary carcinoid tumor of the lung, which is a type of neuroendocrine tumor.

Small Cell Lung Cancer (SCLC): Although less likely, SCLC can present with a solitary lung nodule and has a strong association with paraneoplastic syndromes, which can sometimes mimic the presentation of neuroendocrine tumors.
Pulmonary Metastasis from Another Primary Site: If the patient has a history of another malignancy, the lung nodule could represent a metastasis from that site, emphasizing the need for a thorough review of the patient's oncologic history.

Multiple Endocrine Neoplasia (MEN) Syndromes: If the patient's neuroendocrine tumor was part of a MEN syndrome, there could be multiple primary tumors, including in the lungs, although this would be less common.
Other Rare Neuroendocrine Tumors: Such as a pulmonary neuroendocrine tumor like a typical or atypical carcinoid, or even a large cell neuroendocrine carcinoma, though these are less common than metastasis or primary lung cancer in this context.