Adenocarcinoma of unknown primary site (ACUPS) presenting as a psoas abscess

The presentation of a psoas abscess is commonly seen in conjunction with infection, especially tuberculous. Involvement of the psoas muscles with tumour, however, is extremely rare. We present a case in which adenocarcinoma of unknown primary site infiltrated the psoas muscle, thus mimicking a psoas abscess. A review of this unusual tumour type is discussed.