Clear cell “sugar” tumor of the lung: Diagnostic characteristics of a rare pulmonary tumor: A case report and review of literature

Abstract

Introduction: Clear cell tumors of the lung (CCTLs), also known as “sugar tumors” for an abundant cellular glycogen concentration, are an extremely rare type pulmonary neoplasm. Often, they are incidentally found on chest roentgenogram or computed tomography scan during routine examination. CCTLs usually present with nonspecific symptoms that pose a diagnostic challenge to clinicians. Accordingly, histopathology remains the gold standard for diagnosing. Moreover, some of them can present with either appearances or histopathological features similar to other pulmonary neoplasms under the light microscope, including pulmonary malignancy, thereby causing misdiagnosis prior to or after surgery. Accordingly, herein, we describe a rare case of CCTL, review the literature has been published, and then discuss the benign versus malignant nature of this rare tumor. Patient concerns: A 59-year-old man presented due to a high-density chest nodule in the left diaphragm. The patient’s medical history was unremarkable and he also denied smoking in the past. Diagnosis: Physical examination, there were no noted signs. A new chest contrast-enhanced computed tomography revealed a 3.2 × 2.5 cm, solitary, circular nodule with a smooth edge located in the beside of the left thoracic aorta. Postoperative pathological and immunohistochemical examinations of the surgical specimens revealed a final diagnosis of CCTLs. Interventions: The patient underwent video-assisted thoracoscopic surgery. A wedge resection of left lower lung lobe was carried out and the tumor node was successfully removed alongside normal surrounding parenchyma. Outcomes: The operation was successful. Then the patient recovered completely and continued to do well on postsurgical thoracic surgical clinic visits. The tumor was a benign tumor, and the patient did not require any additional treatment. The patient had been followed-up regularly for 4 years after surgery; she did not experience any complications and remained disease-free. Conclusion: CCTLs should be considered in the differential diagnosis if a patient shows a solitary, circular chest nodule with a smooth edge. They are extremely rare lung tumors that must be differentiated from other lung tumors, especially the malignant tumors. Although pathological and immunohistochemical findings are important for making the diagnosis, the varying histopathological features on microscope make diagnosis difficult. The current case highlights the importance of physicians being aware of and suspecting CCTLs in similar cases, along with knowing the characteristics of CCTLs for the diagnosis and differential diagnosis.