Parosteal lipoma of humerus with a medical history of 24 years: a case report

Parosteal lipoma is an extremely rare benign tumor, responsible for less than 0.1% of primary bone neoplasms and 0.3% of all lipomas, which mainly constitutes of mature adipose tissue with a bony component. Bony lesions are often discovered in patients with this tumor (59.2%), creating the significance of differential diagnosis of malignant tumors. The tumor is known to be related with underlying bony changes including focal cortical hyperostosis, pressure erosion of the underlying bone, and bowing malformation. Here we state a case of a parosteal lipoma appearing in the humerus with a bony excrescence in a 70-year-old male patient, which had the longest medical history (24 years) in documents of the last 50 years. Twenty-four years after the mass was found, he presented with complaints of night pain. MRI presented a large 11 cm x6 cm x5 cm well defined, lobulated mainly fat intensity lesion with a small part of chondroid component measuring 2.7 mm x1.9 mm x0.9 mm in proximal left humerus. The mass was excised, and the pathology demonstrated ossifying parosteal lipoma without features of malignancy. The patient had no recurrence and no complaints for 2 years after the operation. In conclusion, orthopedic surgeons should bear the diagnosis of parosteal lipoma in mind, thus providing appropriate treatment. Surgery is usually ideal treatment, which requires that any periosteal involvement is removed completely.