Tumor-to-Tumor Metastasis: Pulmonary Carcinoid Metastasizing to Solitary Fibrous Tumor

Abstract

Patient: Female, 81Final Diagnosis: Pulmonary carcinoid tumor • solitary fibrous tumorSymptoms: DiaphoresisMedication: —Clinical Procedure: SurgerySpecialty: OncologyObjective:Rare diseaseBackground:Tumor-to-tumor metastasis is an uncommon phenomenon in which a primary tumor metastasizes into another tumor.Case Report:An 81-year-old Asian woman was referred to our hospital for evaluation and treatment of a solid mass in the right middle lung lobe that had rapidly enlarged for 1.5 years compared to that observed over the last 5 years. On computed tomography (CT), the mass was 68×60 mm, and 2 different tumors appeared to exist in the upper portion of the mass. Blood examination findings revealed high serum levels of progastrin-releasing peptide and neuron-specific enolase. Based on the radiographic course of the tumor and elevated levels of tumor markers, we suspected that a new malignant tumor, such as a neuroendocrine tumor, had developed dorsally adjacent to the benign tumor. CT-guided percutaneous needle biopsy of the lung indicated a solitary fibrous tumor (SFT), which did not lead to the diagnosis of another tumor adjacent to the original tumor. Therefore, a right middle lobectomy was performed. The resected specimen contained 2 different tumors: an SFT and a typical carcinoid without mitosis or necrosis. On microscopic examination, they were separated from each other by normal alveolar tissue. In addition, a typical carcinoid was also observed inside the SFT lesion, completely enclosed by the SFT tissue. These findings suggested that the carcinoid metastasized to the SFT in the same lung lobe.Conclusions:To the best of our knowledge, this is the first case of a pulmonary typical carcinoid metastasizing to an intraparenchymal SFT.