Subcutaneous Sacrococcygeal Myxopapillary Ependymoma

54-year-old woman with subcutaneous sacrococcygeal myxopapillary ependymoma.

A, Plain radiograph of the pelvis shows a well-defined ovoid radiopaque mass (arrows) with flocculent and punctate calcifications (arrowheads).

B, Sagittal turbo spin-echo T1-weighted (600/12/4 [TR/TE/excitations]) MR image shows a well-defined, lobulated, partially septated mass in the subcutaneous tissue of the sacrococcygeal region that is heterogeneous in signal intensity. Fibrous capsule (solid arrows) and septa (arrowheads) are of low signal intensity. There are calcifications along the posterior portion (open arrows).

C, Sagittal contrast-enhanced fat-suppressed turbo spin-echo (500/15/3) MR image shows heterogeneous enhancement at the periphery (arrows). The enhancing areas correspond to the areas of high signal intensity on T1-weighted images.

D and E, Sagittal (D) and axial (E) turbo spin-echo T2-weighted (4000/112/3) MR images show markedly heterogeneous signal intensity, suggestive of necrosis, blood degradation products, and/or hemorrhage. Mass is divided into lobules by septa (arrowheads). Note calcifications in posterior portion (open arrows, D). Gm indicates gluteus maximus muscle.

F, Cut surface of the gross specimen shows a well-encapsulated solid mass that is partially divided into lobules by septa (arrowheads). Note hemorrhage (solid arrows) and calcifications (open arrows).

G, The viable tumor cells are noted at periphery, and become attenuated by a predominance of mucoid globules, which were not found in central portion. Hemorrhage (H) and necrosis (N) are noted in center (hematoxylin and eosin, original magnification × 40).

H, Photomicrograph shows collars of cuboidal cells (arrowheads) surrounding a neck of mucin with a centrally located blood vessel (arrows), characteristic findings of myxopapillary ependymoma (hematoxylin and eosin, original magnification × 200). Inset: Immunohistochemical stain for glial fibrillary acidic protein shows diffuse positivity of the tumor cells (original magnification × 200).