Malignant transformation of perianal tailgut cyst: A case report

BACKGROUND: Tailgut cyst is a congenital enterogenous cyst that rarely undergoes malignant transformation. Its clinical manifestations mainly correlate to the mass effect caused by the development of cysts and the infections that originate from these. Furthermore, the complete resection of this cyst is curative. We report our diagnostic and treatment experience with one case of malignant transformation of a perianal tailgut cyst, which was initially misdiagnosed as perianal abscess. CASE SUMMARY: A 72-year-old woman visited our institution with complaints of a refractory nonhealing lesion on the right hip, which repeatedly broke and suppurated for more than 70 years, and aggravated in 4 mo. The patient was given a diagnosis of refractory perianal abscess with repeated incision and drainage procedures. Computed tomography of the pelvic cavity revealed a giant perianal cyst. Subsequent biopsy revealed a tumor with moderate-to-severe glandular epithelial dysplasia, and suggested that this was derived from the developmental cysts in the posterior rectal space. After further clarifying the nature and extent of the tumor by magnetic resonance imaging, total cystic resection was performed. Postoperative histopathological examination confirmed the malignancy, dictating the investigators to add postoperative chemotherapy to the treatment regimen. CONCLUSION: The malignant transformation of perianal tailgut cysts is very uncommon, and this should be differentiated from perianal abscess. Complete surgical removal is curative, and postoperative pathology may determine the necessity of additional postoperative chemotherapy or radiotherapy, which may be beneficial for preventing local recurrence and metastasis.