While not bearing immediate prognostic data, the homeobox gene HOXB13 (which is often seen in prostate cancer) has emerged as a useful immunohistochemical marker for distinguishing MPE from other spinal ependymomas, as shown in a study including 143 spinal neoplasms (54 MPE, 46 spinal ependymomas, and various other tumor types) [13]. The gene discussed is HOXB13; the disease is neoplasm.