Lymphomas presenting and mimicking soft-tissue masses are important to recognize, to avoid unnecessary treatment delays or extensive surgery. We describe a case of primary anaplastic large cell lymphoma (ALCL) arising from a deep skeletal muscle in a middle-aged male. He presented with a two-month history of swelling of his right thigh and mild fever, which led to a diagnosis of abscess formation. Antibiotics were prescribed for two weeks, with little improvement of symptoms. Subsequently, an exploratory surgery, with excision of the mass, demonstrated a ALCL of the psoas muscle, ALK-1 positive.