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Pre-Sacral Masses
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Pre-Sacral Masses | ||
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Related narrative: Pre-Sacral Mass The variety of embryonic remnants found in the retrorectal/presacral space may give rise to a variety of congenital lesions. Most (2/3) presacral lesions are congenital. Other masses are neurogenic, osseous, inflammatory and miscellaneous lesions. Most presacral lesions occur in the pediatric age group and most in this group are benign. Adult masses have a higher incidence of malignancy. Solid masses are more likely to be malignant than cystic. Most such masses are asymptomatic and are discovered incidentally. Most are also palpable on rectal exam. Congenital lesions may be cystic or solid. Cystic lesions include developmental cysts, duplication cysts and anterior meningoceles. Developmental cysts are most common and are derived from all three germ layers. They may be dermoid or epidermoid and are more common in women. They are ectodermal derivatives and are lined with squamous epithelium with or without dermal appendages. They may be heralded by a skin dimple and are prone to infection. In those cases they may be mistaken for a perirectal abscess, pilonidal or fistula-in-ano. Recurrence after I&D may reveal an underlying cyst. Another cystic lesion, tailgut cysts may be enterogenous duplication cysts and/or remnants of the tail that fail to regress. Duplication cysts arise from sequestra of the primitive hindgut. They are thin-walled, may be multilocular and are lined with columnar epithelium. Rectal duplication cysts contain all layers of the rectal wall. Solid presacral masses include chroma, teratoma, adrenal rests, neurogenic and osseous lesions. Chordomas arise from notochord remnants and 30-50% arise in the presacral area. They are the most common malignant retrorectal tumor. They are slow-growing, locally invasive and cause local bone destruction. There is a high local recurrence rate after radical resection and about a 25% ten-year survival rate. Teratomas are true neoplasms derived from all three germ layers and may have cystic and solid components. They have a female and childhood predominance, and have the potential for malignant degeneration, more commonly in adults. Untreated teratomas have a 10% malignant transformation rate with time. They are commonly tightly attached to the coccyx and require en-block resection. Adrenal rests are rare congenital solid lesions and are treated as ectopic adrenal tumors when discovered. Ten percent of rectorectal masses are neurogenic, derived from peripheral nerve tissue. Ependymoma is the most common. These present with pain and neural dysfunction and require radical resection which results in neural deficit. Survival rates are good. Osseous lesions also represent 10% of presacral masses, are usually benign and have a high local recurrence rate. Miscellaneous conditions constitute the remainder of presacral processes. Complications of Crohn's and diverticulitis may present in this space. Metastases, lymphangiomas, demoed, leiomyoma, fibrosarcoma and endothelioma, may also be found. Diagnosis is usually incidental by rectal exam or imaging for other reasons. MRI is the most sensitive and specific modality. Biopsy is almost never indicated because of the possibility of spreading infection from cystic lesions, causing meningitis with meningocele and spreading malignancy (especially chordoma). Unresectable (for technical or comorbid reasons) lesions may be biopsied for therapeutic planning. Lesions extending above the S4 level do best with a transabdominal approach, while lower lesions whose upper limit can be palpated on rectal exam lend themselves to a trans-sacral approach. Larger lesions may do best with a combined approach. Rectal involvement should be ruled out by scope, and rectal resection included for invasive lesions. Sacrococcygeal resection is mandated for posterior invasion. A team approach depending on the nature of the lesion may include colorectal, neuro-, orthopedic and plastic surgeons. primary sacrococcygeal malignancies are radio and chemoresistant, but metastatic lesions may be responsive. References: Dunn KB, Retrorectal tumors, S. CL. NA. 90 (Feb. 2010)
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