Malignant Myoepithelioma Arising from the Upper Arm With Brachial Plexus Involvement: A Rare Case

Malignant myoepitheliomas (MMs) are infrequent, and the site of upper arm is extremely rare. To our knowledge, only two cases occurred in the upper arms according to previous reports.

A 73-year-old male presented with a growing mass in his left upper arm one year prior to surgery. After a needle biopsy, histopathological analysis revealed the mass to be a myxoid sarcoma but did not reach to definite diagnosis. The tumor was excised from the brachial plexus. The brachial artery and vein were preserved. The radial nerve was strongly adherent to the tumor, however, the radial nerve, the median, ulnar, and radial nerves could be preserved. Histopathological examination and fusion gene analysis of the resected specimen revealed MM. As adjuvant therapy, postoperative intensity-modulated radiation therapy (IMRT) was administered. At the current follow-up, for four years after surgery, no local recurrence or metastasis has been observed, and the patient has good limb function.

We report on an extremely rare case of MM located in upper arm. Resection with radiation therapy may be contributing to a better prognosis and function, although further studies are required regarding treatment validity.