A Rare Case of Giant Hypothenar Lipoma with Intermuscular Extension Causing Ulnar Nerve Irritation

Background: Lipomas are the most common benign mesenchymal tumors of soft tissue but are rare in the hand and exceptionally uncommon in the hypothenar region. We report a 45-year-old female with a gradually progressive swelling in the right hypothenar eminence over three years, accompanied by occasional tingling along the ulnar side of the hand. Clinical examination revealed a firm, mildly mobile mass with reduced grip strength and positive Tinel’s sign. MRI demonstrated a well-defined, fat-signal lesion extending into intermuscular plane consistent with lipoma. Fine-needle aspiration cytology was inconclusive, suggesting granulomatous inflammation, highlighting the diagnostic limitations of FNAC in deep-seated lipomas. The patient underwent complete surgical excision, revealing a well-encapsulated lipoma displacing but not infiltrating the digital branch of the ulnar nerve. Histopathology confirmed benign lipoma without granulomatous features. Postoperative recovery was uneventful with full functional restoration. This case underscores keeping lipoma as an important differential diagnosis in hand swellings and highlights the importance of clinico-radiological correlation when FNAC findings do not align with imaging and clinical impressions.

Keywords: ulnar nerve entrapment, benign hand swelling, peripheral nerve tumor, mri of lipoma, benign soft tissue tumor, hand tumor case report, ulnar tunnel syndrome, giant palmar lipoma, intermuscular lipoma, hypothenar lipoma.