Benign Presacral Tumor Mimicking a Pilonidal Abscess: A Diagnostic Pitfall

Presacral tumors are rare and heterogeneous neoplasms that develop in the space between the rectum and sacrum. Their low prevalence and diverse embryologic origins often complicate diagnosis and management. We present the case of a 43-year-old woman who was initially misdiagnosed with a pilonidal abscess, later identified as a benign presacral tumor. PATIENT DESCRIPTION A 43-year-old woman presented with a gradually enlarging mass in the pilonidal region over the course of several months. She was referred to our colorectal clinic with a presumptive diagnosis of a pilonidal abscess made by her primary care physician. The patient was otherwise healthy, with no complaints of pain, fever, chills, or unintentional weight loss. On physical examination, a non-tender mass was palpated over the coccygeal region. Notably, there were no midline pits or visible hair [Figure 1A]. Given the atypical presentation, a magnetic resonance imaging (MRI) was performed, which revealed a well-defined, large presacral bilobular thin-walled cystic mass, posterior to the rectum, without any post contrast ring-enhancement or intramural solid nodule [Figure 1B]. Due to the low anatomical position of the mass relative to the sacrum, a Kraske approach was selected for surgical excision. Under general anesthesia, the patient was placed in the prone jackknife position. A vertical midline incision was made 7 cm cephalad to the anal verge, over the coccyx. This position exposed a well-encapsulated, large presacral tumor [Figure 1C], which was excised en-bloc along with the tip of the coccyx [Figure 1D, Figure 1E]. The specimen was sent for pathological evaluation, which revealed a retrorectal epidermal cyst. The patient's postoperative course was uneventful, and she was discharged on postoperative day one. Informed consent was obtained from the patient.