Rapidly growing mediastinal mature cystic teratoma with increased FDG uptake: challenging the paradigm of indolent growth.

BACKGROUND: Mature cystic teratomas of the mediastinum are typically germ cell tumors with indolent growth, with documented annual growth rates often less than 5 centimeters. We report a case with an abnormal growth rate (Average diameter growth rate 7.14 mm/month) and significant increased 18 F fluorodeoxyglucose (18 F FDG) uptake, which challenges conventional diagnostic concepts. CASE PRESENTATION: A 34-year-old female presented with progressive chest tightness. Serial CT imaging revealed a right anterior superior mediastinal mass that grew from approximately 1.5 cm in long diameter to 6.5 cm over 7 months (Average diameter growth rate 7.14 mm/month). 18 F fluorodeoxyglucose Positron Emission Tomography-Computed Tomography(18 F-FDG PET/CT) revealed the lesion with high metabolic heterogeneity, and the maximum standardized uptake value (SUVmax 6.9). Pathological examination after thoracoscopic-assisted complete resection confirmed the diagnosis of mature cystic teratoma with mature glial components. CONCLUSION: This case suggests that lesions with rapid growth and significantly increased FDG uptake do not necessarily indicate malignant transformation of teratoma. Multidisciplinary decision-making should be based on dynamic quantitative imaging and metabolic feature analysis.Categories: Pathology, Oncology, Pulmonology.