Extraspinal sacrococcygeal myxopapillary ependymoma mimicking pilonidal disease in an adolescent: a case report

Abstract Background: Extraspinal sacrococcygeal myxopapillary ependymoma (MPE) can mimic pilonidal disease and present to colorectal surgeons before its neoplastic nature is recognized. Case presentation: We report a 15-year-old boy with a progressively enlarging natal-cleft mass present for more than 3 years, without recurrent infection, drainage, a midline pit, or a visible sinus opening. Ultrasonography showed a 4.8 × 3.1 × 2.3 cm solid hypoechoic lesion with heterogeneous echoes and appreciable internal vascularity. Pilonidal disease remained the working diagnosis, and preoperative magnetic resonance imaging (MRI) was not performed. Surgery revealed an encapsulated solid tumor without hair, a sinus tract, or an abscess. The lesion was excised en bloc without visible capsular rupture. Histological examination and positivity for glial fibrillary acidic protein and S-100 supported MPE, CNS WHO grade 2. Microscopic margin status was not documented. Postoperative whole-spine MRI identified no intraspinal lesion. At approximately 2 months, the wound had healed and no new local mass or neurological symptoms were detected clinically. Conclusions: This case highlights the need to reconsider pilonidal disease when clinical findings and ultrasonography are discordant. For colorectal surgeons, further evaluation should clarify the relationship of an atypical mass to the anal sphincter complex, rectum, coccyx, and spinal canal before definitive surgery. An unexpected solid tumor warrants intraoperative reassessment rather than automatic continuation of a sinus-directed procedure. The short follow-up and undocumented margins preclude conclusions about durable oncological control.