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An unexpected mass of the urachus: a case report

2014; Elsevier BV; Volume: 211; Issue: 4 Linguagem: Inglês

10.1016/j.ajog.2014.06.011

1097-6868

Monica C. Pasternak, Jonathan D. Black, Natália Buza, Masoud Azodi, Aileen M. Gariepy,

Urological Disorders and Treatments

The urachus is a remnant of the urogenital sinus and allantois, which persists after antenatal involution. Despite its rudimentary postnatal presence, it can undergo metaplasia and tumor formation. Malignant transformation of the urachus is rare. However, these tumors can recur and develop pseudomyxoma peritonei. Thus, they should remain on the differential for any female patient with a pelvic mass. A 28-year old G9P2062 presented at 8 weeks' gestation requesting pregnancy termination. On ultrasound, a single live intrauterine pregnancy was visualized. Also identified was a left-sided 8- × 7- × 6-cm complex echogenic mass with thickened septations, heterogeneous appearance, and fluid-fluid levels suspicious for a mature cystic teratoma. Surgical termination of pregnancy and diagnostic laparoscopy was planned. Intraoperatively a multiloculated midline mass was identified and excised. Final pathology identified a mucinous urachal neoplasm of low malignant potential. The patient followed up with urology and underwent surgical staging. Midline location is a key feature that helps distinguish ovarian masses from urachal or bladder masses. Many urachal and bladder neoplasms are managed with complete surgical excision and staging, illustrating the importance of preoperative identification. If laterality of a mass is unclear, further imaging is recommended to characterize the mass preoperatively. This case also reveals the feasibility of a minimally invasive abdominal wall mass resection. The urachus is a remnant of the urogenital sinus and allantois, which persists after antenatal involution. Despite its rudimentary postnatal presence, it can undergo metaplasia and tumor formation. Malignant transformation of the urachus is rare. However, these tumors can recur and develop pseudomyxoma peritonei. Thus, they should remain on the differential for any female patient with a pelvic mass. A 28-year old G9P2062 presented at 8 weeks' gestation requesting pregnancy termination. On ultrasound, a single live intrauterine pregnancy was visualized. Also identified was a left-sided 8- × 7- × 6-cm complex echogenic mass with thickened septations, heterogeneous appearance, and fluid-fluid levels suspicious for a mature cystic teratoma. Surgical termination of pregnancy and diagnostic laparoscopy was planned. Intraoperatively a multiloculated midline mass was identified and excised. Final pathology identified a mucinous urachal neoplasm of low malignant potential. The patient followed up with urology and underwent surgical staging. Midline location is a key feature that helps distinguish ovarian masses from urachal or bladder masses. Many urachal and bladder neoplasms are managed with complete surgical excision and staging, illustrating the importance of preoperative identification. If laterality of a mass is unclear, further imaging is recommended to characterize the mass preoperatively. This case also reveals the feasibility of a minimally invasive abdominal wall mass resection. The urachus is a fibrous remnant of the urogenital sinus and allantois, a structure connecting the urinary bladder to the umbilicus during embryogenesis.1Hoffman B.L. Williams J.W. Williams gynecology.2nd ed. McGraw-Hill Medical, New York2012Google Scholar The involution of the urachus usually transpires antenatally, and it subsequently becomes a vestigial remnant that can undergo metaplasia and subsequent tumor formation.2Schell A.J. Nickel C.J. Isotalo P.A. Complex mucinous cystadenoma of undetermined malignant potential of the urachus.Can Urol Assoc J. 2009; 3: E39-E41PubMed Google Scholar A patent urachus is found in 1 in 200,000 live births and 1 in 5000 adults have an urachal cyst at autopsy.3Gore R.M. Levine M.S. High-yield imaging: gastrointestinal. Saunders/Elsevier, Philadephia, PA2010Google Scholar Malignant transformation of the urachus to urachal adenocarcinoma is rare, represents <1% of all bladder tumors,4Siefker-Radtke A. Urachal adenocarcinoma: a clinician's guide for treatment.Semin Oncol. 2012; 39: 619-624Abstract Full Text Full Text PDF PubMed Scopus (89) Google Scholar and occurs annually in 20 per 100,000 women and men.5National Cancer Institute. Surveillance, Epidemiology, and End Results Program. SEER Stat Fact Sheets: Bladder Cancer. Available at: http://seer.cancer.gov/statfacts/html/urinb.html. Accessed May 22, 2014.Google Scholar Primary mucinous urachal neoplasms of low malignant potential are exceedingly rare, and are subject to recurrence and pseudomyxoma peritonei.2Schell A.J. Nickel C.J. Isotalo P.A. Complex mucinous cystadenoma of undetermined malignant potential of the urachus.Can Urol Assoc J. 2009; 3: E39-E41PubMed Google Scholar, 6Carr N.J. McLean A.D. A mucinous tumour of the urachus: adenoma or low grade mucinous cystic tumor of uncertain malignant potential?.Adv Clin Pathol. 2001; 5: 93-97PubMed Google Scholar, 7Choi J.W. Lee J.H. Kim Y.S. Urachal mucinous tumor of uncertain malignant potential: a case report.Korean J Pathol. 2012; 46: 83-86Crossref PubMed Scopus (6) Google Scholar These neoplasms are often managed with complete surgical excision, making preoperative identification important to facilitate proper surgical management.2Schell A.J. Nickel C.J. Isotalo P.A. Complex mucinous cystadenoma of undetermined malignant potential of the urachus.Can Urol Assoc J. 2009; 3: E39-E41PubMed Google Scholar Consequently, urachal tumors should be considered for any female patient with a pelvic mass. A 28-year old G9P2062 presented requesting pregnancy termination. On transvaginal ultrasound, a single live 8-week size intrauterine pregnancy was visualized. Additionally, an 8- × 7- × 6-cm complex echogenic mass, thought to arise from the left adnexa, was visualized superior to the bladder. The mass demonstrated thickened septations, heterogenous appearance, and fluid-fluid levels, findings suspicious for a mature cystic teratoma (MCT) (Figure 1). Surgical termination of pregnancy, intrauterine device placement, and diagnostic laparoscopy was planned. Intraoperatively, a multiloculated, cystic, midline mass was noted arising from the anterior abdominal wall in close proximity to the bladder (Figure 2). Surgical consultation with general surgery and gynecology oncology was obtained. The peritoneum was undermined and omentum was dissected from the mass. The mass was noted to be independent of bladder, ureters, and surrounding vasculature, and was dissected away from the peritoneum and excised with at least 1-cm margins. The appendix appeared normal and no gastrointestinal tract involvement was identified. The remainder of the pelvis including the adnexa appeared normal. A 6-cm posterior colpotomy was made under direct and laparoscopic visualization. The mass was removed en-bloc through the colpotomy, which was closed in a running locked fashion with 2-0 polyglactin suture. While urachal mass was now part of the differential diagnosis, the patient was not preoperatively consented for staging. Therefore, no further investigation, including frozen section, was performed. Postoperatively the patient did well and was discharged on postoperative day 1.Figure 2Intraoperative image of pelvic massShow full captionIntraoperative image depicting adherence of peritoneum and omentum to pelvic mass and relationship of pelvic mass to patient's uterus.Pasternak. Unexpected urachal mass. Am J Obstet Gynecol 2014.View Large Image Figure ViewerDownload Hi-res image Download (PPT) Intraoperative image depicting adherence of peritoneum and omentum to pelvic mass and relationship of pelvic mass to patient's uterus. Pasternak. Unexpected urachal mass. Am J Obstet Gynecol 2014. Pathology revealed a mucin-filled cyst (Figure 3) lined by intestinal-type mucinous epithelium with mild cytological atypia and areas of villous and undulating epithelial proliferation. Significant mucin extravasation with focal clusters of tumor cells into the cyst wall and surrounding fibroadipose tissue and smooth muscle were present. The tumor cells were diffusely positive for CDX2 and CK20. Immunostain was negative for CK7. Final pathologic diagnosis was mucinous urachal neoplasm of low malignant potential. The patient was referred to urology for further treatment. Given the tumor's rarity, it was treated as an urachal adenocarcinoma and the patient underwent a radical umbilectomy, urachal excision, partial cystectomy, omentectomy, and bilateral pelvic lymphadenectomy. There was no evidence of carcinoma in any of the specimens. The patient received no additional therapy and is currently disease free. We describe the case of a 28-year-old woman presenting with an undesired pregnancy and a mass suspicious for a left-sided MCT incidentally found on transvaginal ultrasound. A midline mass was encountered intraoperatively and excised, and postoperative pathologic examination revealed an urachal mucinous neoplasm of low malignant potential. Our patient was referred to the urology service for appropriate staging. MCT is the most common germ cell tumor. It accounts for 10-20% of all ovarian masses and is most common during childbearing years. The incidence of MCT ranges from 1.2-14.2 cases per 100,000 per year.8Hackethal A. Brueggmann D. Bohlmann M.K. Franke F.E. Tinneberg H.R. Munstedt K. Squamous-cell carcinoma in mature cystic teratoma of the ovary: systematic review and analysis of published data.Lancet Oncol. 2008; 9: 1173-1180Abstract Full Text Full Text PDF PubMed Scopus (226) Google Scholar MCTs demonstrate a broad spectrum of findings on any imaging modality, ranging from purely cystic with a densely echogenic tubercle (Rokitansky nodule), to complex with components of all 3 germ cell layers, to noncystic and composed predominantly of fat and sebaceous material.9Outwater E.K. Siegelman E.S. Hunt J.L. Ovarian teratomas: tumor types and imaging characteristics.Radiographics. 2001; 21: 475-490Crossref PubMed Scopus (437) Google Scholar Fluid-fluid levels are characteristic and represent sebum floating above echogenic aqueous fluid. On computed tomography (CT) and magnetic resonance imaging (MRI), fat attenuation within an adnexal cyst, with or without wall calcification, is diagnostic for MCT. Mais et al10Mais V. Guerriero S. Ajossa S. Angiolucci M. Paoletti A.M. Melis G.B. Transvaginal ultrasonography in the diagnosis of cystic teratoma.Obstet Gynecol. 1995; 85: 48-52Crossref PubMed Scopus (102) Google Scholar conducted a prospective study in which ultrasound screening showed 58% sensitivity and 99% specificity for MCTs, and transvaginal ultrasound showed 85% sensitivity and 98% specificity for differentiating MCTs from other masses. However, CT and MRI are more sensitive for fat. Overall MRI has improved sensitivity of 92-100% and similar specificity (99-100%) for diagnosing MCTs.11Heuck A. Abdominal and pelvic MRI. New York, NY: Springer Berlin Heidelberg; 2012.Google Scholar There is no evidence about how often MCTs appear in the midline. In our case, given the prevalence of MCTs, the ultrasound appearance of the mass, including the presumed left-sided origin, the preoperative suspicion for MCT seemed reasonable. Urachal masses are characterized by midline supravesical location, adjacent to the anterior abdominal wall in the space of Retzius, and include neoplastic, benign, and infectious causes. When suspected preoperatively, urachal lesions are best imaged by cross-sectional techniques, which enhance and differentiate their nature, size, and location. While ultrasonography can delineate the tumor as a complex midline mass cephalad to the bladder, multiplanar CT or MRI imaging can better demonstrate the tumor's anatomic relationships to other structures. Additionally, ultrasound is limited by technical ability and the patient's body habitus. Ultimately, MRI offers superior imaging for the sagittally oriented urachus, as its oblique anatomic orientation makes coronal and sagittal MRI views particularly edifying. MRI also highlights local disease extension or systemic metastases.12Roy C. Tumour pathology of the bladder: the role of MRI.Diagn Interv Imaging. 2012; 93: 297-309Crossref PubMed Scopus (8) Google Scholar Urachal carcinomas may be solid, cystic, or a combination, and often have mucinous content. Additional characteristic findings include psammomatous calcification, which occurs in 50-70% of urachal carcinomas.13Krysiewicz S. Diagnosis of urachal carcinoma by computed tomography and magnetic resonance imaging.Clin Imaging. 1990; 14: 251-254Abstract Full Text PDF PubMed Scopus (15) Google Scholar Therefore, if laterality of a pelvic mass is unclear, MRI should be considered. Only 2 cases of urachal mucinous neoplasms of low malignant potential are reported in the English-language literature.2Schell A.J. Nickel C.J. Isotalo P.A. Complex mucinous cystadenoma of undetermined malignant potential of the urachus.Can Urol Assoc J. 2009; 3: E39-E41PubMed Google Scholar, 6Carr N.J. McLean A.D. A mucinous tumour of the urachus: adenoma or low grade mucinous cystic tumor of uncertain malignant potential?.Adv Clin Pathol. 2001; 5: 93-97PubMed Google Scholar, 7Choi J.W. Lee J.H. Kim Y.S. Urachal mucinous tumor of uncertain malignant potential: a case report.Korean J Pathol. 2012; 46: 83-86Crossref PubMed Scopus (6) Google Scholar These tumors are similar to the more common appendiceal low-grade mucinous neoplasms and thus may be associated with pseudomyxoma peritonei, and have potential for local recurrence.6Carr N.J. McLean A.D. A mucinous tumour of the urachus: adenoma or low grade mucinous cystic tumor of uncertain malignant potential?.Adv Clin Pathol. 2001; 5: 93-97PubMed Google Scholar, 14Vargas H.A. Barrett T. Sala E. MRI of ovarian masses.J Magn Reson Imaging. 2013; 37: 265-281Crossref PubMed Scopus (37) Google Scholar Therefore, complete surgical excision is paramount. If intraoperative excision is attempted, a patent urachal cyst should also be considered as inadvertent resection could lead to uremia and peritoneal irritation. Midline location is one of the key features that can distinguish an ovarian mass from an urachal or bladder mass. If suspected preoperatively, an MRI should be considered as it is highly specific and sensitive for identifying MCTs9Outwater E.K. Siegelman E.S. Hunt J.L. Ovarian teratomas: tumor types and imaging characteristics.Radiographics. 2001; 21: 475-490Crossref PubMed Scopus (437) Google Scholar, 14Vargas H.A. Barrett T. Sala E. MRI of ovarian masses.J Magn Reson Imaging. 2013; 37: 265-281Crossref PubMed Scopus (37) Google Scholar and visualizing the topography of the urachus.12Roy C. Tumour pathology of the bladder: the role of MRI.Diagn Interv Imaging. 2012; 93: 297-309Crossref PubMed Scopus (8) Google Scholar When a midline mass is encountered intraoperatively, an urachal mass should be considered and urology consultation obtained. This case also reveals the feasibility of a minimally invasive abdominal wall mass resection.