This report describes a patient with a rare huge epithelioid malignant peripheral nerve sheath tumor (MPNST) in the left axilla. A male in his 70s was admitted to our hospital for evaluation of a growing tumor in his left axilla. The tumor was solid and immovable. Examination of a biopsy specimen resulted in a diagnosis of epithelioid MPNST. Two weeks after the biopsy was performed, the tumor grew to 20 cm and became painful, and the patient was unable to feel pressure on his upper arm. Immediately before surgery to remove the tumor, computed tomography suggested the presence of lung metastases. The patient and his family were informed of his disease state, and they elected surgical treatment to ease the symptoms associated with tumor enlargement. Systemic metastases appeared soon after the surgery, and the patient died within 11 weeks. Comparative genomic hybridization (CGH) analysis showed that this tumor was chromosomally unstable, with impairments in gene expression.