A80-4-47 Incidental Pleural Well-differentiated Liposarcoma in a Patient With History of Papillary Thyroid Carcinoma: A Case Report

Primary pleural well-differentiated liposarcoma is a rare mesenchymal tumor, typically discovered incidentally due to its indolent growth. Management is challenging because of the tumor’s slow progression, nonspecific symptoms, and resemblance to other thoracic diseases. In contrast, papillary thyroid carcinoma is a prevalent endocrine malignancy with a well-established clinical course. The coexistence of both conditions in a single patient is rare, and few case reports underscore the importance of comprehensive long-term surveillance and multidisciplinary management.A 47-year-old woman with Stage II papillary thyroid carcinoma underwent partial, then total, thyroidectomy followed by radioactive iodine therapy in 2004. In 2016, routine imaging incidentally identified a right pleural mass. CT-guided biopsy established the diagnosis of primary well-differentiated liposarcoma of the pleura. Although surgical intervention was recommended, the patient declined due to the absence of symptoms. Follow-up imaging in 2018 revealed only fibrous tissue changes without evidence of tumor progression. The patient was lost to follow-up until 2025. A PET scan in June 2025 demonstrated a stable pleural mass (8.4 x 5.4 x 7.8 cm) with mild FDG uptake (SUV 2.2), without invasion or pleural effusion. Additional findings included a non-FDG-avid spiculated lesion and a rounded prevascular lymph node with low metabolic activity. A possible recurrent focus of papillary thyroid carcinoma near the right thyroid bed was also detected, prompting recommendations for serum thyroglobulin measurement and a whole-body iodine scan. Despite these findings, the patient remained asymptomatic with normal vital signs and physical examination. Following a comprehensive cardiopulmonary assessment, including pulmonary function testing, the pleural mass was surgically excised. Postoperative recovery was uneventful.This case illustrates the exceptional rarity of concurrent primary pleural well-differentiated liposarcoma and papillary thyroid carcinoma. It underscores the necessity of individualized assessment of tumor behavior and recurrence risk. The prolonged stability and low metabolic activity of the liposarcoma support basing surgical decisions on the patient’s overall clinical status rather than solely on tumor growth kinetics. Additionally, the case highlights the importance of multimodal imaging and multidisciplinary collaboration in managing complex presentations. This abstract is funded by: none