Parosteal lipomas associated with an underlying osteochondroma originating from the metatarsal and cuneiform bones: a rare case report.

Introduction and importance: Parosteal lipoma is an uncommon benign tumor that can arise in various parts of the body. Although cases of solitary parosteal lipoma combined with osteochondroma have been occasionally reported, this report describes a unique case in which parosteal lipoma and osteochondroma occurred simultaneously on the metatarsal and cuneiform bones. Case presentation: A 36-year-old female presented with a subcutaneous mass on the dorsum of the left foot. A computed tomography scan revealed bony protrusions on the first metatarsal and medial cuneiform bones, which were considered exostoses. She underwent surgical resection. Notably, lipomas adjacent to the two exostoses were identified intraoperatively, and these lipomas were interconnected. Histopathological examination confirmed the diagnosis of a lipoma combined with osteochondroma. The patient achieved an uneventful recovery. Clinical discussion: In previous literature, cases involving the synchronous occurrence of two or more parosteal lipomas have not been reported. Accurate diagnosis relies on a combination of thorough physical examination and imaging evaluation. Given the reported risk of malignant transformation of bony lesions, the relevant lesions and their surrounding periosteum should be completely resected during surgery, and long-term follow-up should be conducted postoperatively to prevent lesion recurrence. Conclusion: Parosteal lipomas may arise synchronously at separate small osseous regions. Complete resection of the lesion and adjacent periosteum is recommended to minimize the risk of local recurrence. Long-term follow-up, adhering to the surveillance criteria for malignant tumors, is clinically imperative.