Myelolipoma mimicking osteosarcoma in the distal femur

Takao Sakai; Hisaki Aiba; Motoo Nakagawa; Hideo Hattori; Hideki Murakami; Hiroaki Kimura

doi:10.1016/j.ijscr.2021.105997

Myelolipoma mimicking osteosarcoma in the distal femur

Int J Surg Case Rep. 2021 Jun:83:105997. doi: 10.1016/j.ijscr.2021.105997. Epub 2021 May 21.

Authors

Takao Sakai¹, Hisaki Aiba², Motoo Nakagawa³, Hideo Hattori⁴, Hideki Murakami¹, Hiroaki Kimura¹

Affiliations

¹ Department of Orthopaedic Surgery, Nagoya City University, 1, Kawasumi, Mizuho-cho, Mizuho-ku, Nagoya, Aichi 467-8601, Japan.
² Department of Orthopaedic Surgery, Nagoya City University, 1, Kawasumi, Mizuho-cho, Mizuho-ku, Nagoya, Aichi 467-8601, Japan. Electronic address: h-aiba@med.nagoya-cu.ac.jp.
³ Department of Radiology, Nagoya City University, 1, Kawasumi, Mizuho-cho, Mizuho-ku, Nagoya, Aichi 467-8601, Japan.
⁴ Department of Pathology and Molecular Diagnostics, Nagoya City University, 1, Kawasumi, Mizuho-cho, Mizuho-ku, Nagoya, Aichi 467-8601, Japan.

Abstract

Introduction and importance: Periosteal reactions indicate malignant bone tumors, including osteosarcoma; establishing an accurate diagnosis is key to determining the most appropriate treatment strategy. We describe a rare case of myelolipoma in the distal femur metaphysis with massive extraskeletal lesions and periosteal reactions.

Case presentation: A 25-year-old woman was referred to our hospital to treat a gradually expanding mass around her knee that grew to the size of a baby's head. She had a history of hydrocephalus caused by congenital cytomegalovirus infection and was bedridden for life. Radiography showed a prominent osteoblastic rim and osteolytic lesion with a moth-eaten appearance. Osteosarcoma was suspected due to excessive extraskeletal invasion and periosteal reactions. T1- and T2-weighted magnetic resonance images showed a high-signal-intensity homologous lesion. Biopsy specimens contained adipose and hematopoietic tissues. A myelolipoma was diagnosed. Due to her fragility, surgical intervention was suspended. Two years after diagnosis, the tumor size did not change.

Clinical discussion: Myelolipomas are benign tumors that typically arise from the adrenal gland and rarely develop in the extremities. This type of tumor typically does not cause any tumor-related symptoms or endocrine disturbances and has been reported as a type of incidentaloma. To effectively manage myelolipoma patients, differential diagnosis of tumors mimicking malignant bone tumors is important.

Conclusion: We successfully managed a destructive ectopic myelolipoma in the distal femoral metaphysis, with massive extraskeletal lesions and periosteal reactions. Clinicians should appropriately differentiate myelolipoma from tumors mimicking malignant bone tumors.

Keywords: Extra-adrenal myelolipoma; Malignant bone tumor; Myelolipoma; Osteosarcoma.