Lateral Abdominal Wall Hibernoma: A Rare Case From the Maldives

Hibernoma is a rare, benign soft tissue tumor originating from residual fetal brown adipose tissue and derives its name from its histological resemblance to brown fat in hibernating animals. These tumors most commonly occur in adults during the third and fourth decades of life, typically in the thigh, though other sites include the axilla, shoulder, back, neck, and retroperitoneum. Complete surgical excision is the treatment of choice and carries an excellent prognosis. We report a case of symptomatic hibernoma arising in the lateral abdominal wall of a 35-year-old Maldivian woman who presented with an eight-month history of a progressively enlarging, dull aching mass in the right lumbar region. Magnetic resonance imaging (MRI) revealed a well-defined 9.7 × 6.6 × 5.7 cm soft tissue mass within the myofascial plane between the external and internal oblique muscles. The mass was completely excised, and histopathological examination confirmed hibernoma, showing a well-circumscribed, lobulated mass with a tan-yellow to reddish-brown cut surface. Microscopically, sheets of polygonal cells with multivacuolated granular cytoplasm and small central nuclei were observed, with no atypia, necrosis, or mitotic figures. The patient remained asymptomatic at one-month follow-up. To the best of our knowledge, this is the first reported case of hibernoma from the Maldives and one of the few cases arising from the abdominal wall musculature, with the unique feature of originating from the internal oblique muscle. This case highlights the importance of considering hibernoma in the differential diagnosis of deep-seated soft tissue tumors, particularly when imaging reveals a well-defined, heterogeneous mass with benign characteristics.