Disseminated Nocardia farcinica Infection Presenting as Multiple Intramuscular Abscesses Mimicking Skeletal Muscle Metastases in a Patient With Hepatocellular Carcinoma.

A 67-year-old man with hepatocellular carcinoma and a previously resected pulmonary metastasis was receiving prednisolone for immune-related interstitial nephritis. Two months after pulmonary metastasectomy, multiple pulmonary nodules and painful intramuscular masses developed in the right forearm, left gluteus medius, and left obturator internus. The lesions were initially interpreted as metastases, and palliative radiotherapy was initiated. At the initial radiation oncology consultation, the patient was afebrile but had right forearm edema, neutrophilic leukocytosis, and an elevated C-reactive protein level. After 21 Gy in seven fractions to the right forearm, rapidly progressive swelling and pain led to emergency decompression for acute compartment syndrome. A purulent collection was identified; blood culture grew Nocardia farcinica, and direct smear examination of aspirated fluid showed branching filamentous Gram-positive bacteria consistent with Nocardia species. Subsequent brain magnetic resonance imaging demonstrated multiple cerebral abscesses. Radiotherapy was discontinued, and the patient improved after drainage and prolonged combination antimicrobial therapy. This case demonstrates that multifocal nocardial infection may be mistaken for metastatic disease in a corticosteroid-treated patient with cancer and emphasizes the need to integrate physical examination, laboratory abnormalities, and imaging findings before treating unbiopsied soft-tissue lesions.