{"paper_id":"9ce41ef8-4d57-4434-a60c-8392bfe3bd1a","body_text":"Review began\n 01/29/2024 \nReview ended\n 02/22/2024 \nPublished\n 02/29/2024\n© Copyright \n2024\nKatsikatsos et al. This is an open access\narticle distributed under the terms of the\nCreative Commons Attribution License CC-\nBY 4.0., which permits unrestricted use,\ndistribution, and reproduction in any\nmedium, provided the original author and\nsource are credited.\nRenal Endometriosis Mimics Renal Cell\nCarcinoma in a Hypoplastic Kidney: A Case\nReport\nPanagiotis Katsikatsos \n, \nKonstantinos Douroumis \n, \nDimitrios Goutas \n, \nHarikleia Gakiopoulou \n,\nPeriklis Anastasiou \n, \nIoannis Anastasiou \n1.\n Urology, Laiko General Hospital, Athens, GRC \n2.\n Pathology, National and Kapodistrian University of Athens School\nof Medicine, Athens, GRC \n3.\n Medicine, University Hospital of Ioannina, University of Ioannina, Ioannina, GRC\nCorresponding author: \nPanagiotis Katsikatsos, \npkatsikatsos@gmail.com\nAbstract\nRenal endometriosis\n is a rare disorder of cases of urinary tract endometriosis. A 42-year-old woman\npresented at our outpatient department with an incidental painless mass on her left hypoplastic kidney\nrevealed on an abdominal ultrasound. Abdominal and pelvic examinations revealed no abnormal findings. A\ncomputed tomography (CT) scan revealed an anterolateral slightly enhanced left renal mass that measured\n1.2 cm in diameter. Furthermore, CT did not reveal any evidence of abdominal or thoracic metastasis. There\nare a few case reports in the literature of tumors in specimens from patients who underwent nephrectomy\nfor hypoplastic kidneys, but discriminating between benign and malignant masses is difficult unless a\nnephrectomy is performed. Given the radiological findings and the impaired function of the hypoplastic\nkidney, laparoscopic radical nephrectomy was recommended. The procedure was performed under general\nanesthesia without intraoperative or postoperative complications. Microscopic examination revealed several\nfindings consistent with a diagnosis of renal endometriosis. The patient had no symptoms at her last follow-\nup visit. This case highlights that renal endometriosis can mimic renal cell carcinoma and awareness of this\nentity should be raised, as it can be asymptomatic, especially when located in a hypoplastic kidney.\nCategories:\n Urology\nKeywords:\n case report, renal endometriosis, renal hypoplasia, renal tumour, endometriosis\nIntroduction\nEndometriosis is a common gynecologic condition characterized by the implantation of endometrial tissue\nin extrauterine sites. It is broadly divided into endopelvic and extrapelvic diseases \n[1]\n. The incidence of\nendometriosis varies from approximately 6% to 10% in women of reproductive age, and it commonly\nmanifests as chronic pelvic pain \n[2]\n. Extrapelvic sites of endometriosis include the abdominal wall, thorax,\ngastrointestinal tract, and urinary tract. Endometriosis in the urinary tract is rare and accounts for 1-2% of\nall cases. The bladder and ureter are the most commonly affected organs, with a prevalence of 85% and 15%,\nrespectively, while the kidney and urethra account for less than 1% \n[3]\n. The most common presentations of\nrenal endometriosis are flank pain and gross haematuria, although many cases present with vague,\nnonspecific symptoms. Hypoplastic kidneys result from multiple contributing factors, such as congenital\nhypoplasia, chronic urinary tract infections, renovascular ischemia, urological interventions, and surgeries\n[4]\n. There are a few case reports in the literature of tumors in specimens from patients who underwent\nnephrectomy for hypoplastic kidneys. The incidence rate is low, varies among studies, and is associated with\npatient characteristics \n[5-7]\n. We report the case of a 42-year-old woman who underwent laparoscopic left\nradical nephrectomy for renal endometriosis that was preoperatively misinterpreted as a malignant renal\ntumor. This report aims to share our experience and raise awareness that pelvic pain in women of\nchildbearing age should be approached with a high level of suspicion to avoid misdiagnosis of renal\nendometriosis.\nCase Presentation\nA 42-year-old woman presented to our outpatient clinic for a left kidney mass detected on an abdominal\nfollow-up ultrasound for the atrophic kidney. Her medical history included hypertension and depression, for\nwhich she was on medication. Her surgical history was notable for thyroidectomy for papillary thyroid\ncancer and cervical lymph node dissection for a metastatic lymph node five years ago. The gynecological\nhistory was uneventful, with a normal menstruation cycle and no symptoms of dysmenorrhea or\ndyspareunia. Her family history was remarkable for hypertension and diabetes mellitus from the paternal\nside and unremarkable on the maternal side. The patient’s medical history included an incidental diagnosis\nof left kidney hypoplasia 17 years ago on an abdominal ultrasound scan.\nA CT scan following the incidental renal hypoplasia finding did not reveal any pathological findings. A\ndimercaptosuccinic acid (DMSA) scan showed left kidney involvement in renal function of 8%. Patient\nfollow-up included a yearly ultrasound scan.\n1\n1\n2\n2\n3\n1\n \n Open Access Case\nReport\n \nDOI:\n 10.7759/cureus.55280\nHow to cite this article\nKatsikatsos P, Douroumis K, Goutas D, et al. (February 29, 2024) Renal Endometriosis Mimics Renal Cell Carcinoma in a Hypoplastic Kidney: A\nCase Report. Cureus 16(2): e55280. \nDOI 10.7759/cureus.55280\n\nIn the 2022 follow-up ultrasound, a small left renal mass with a diameter of 1 cm was observed. On\npresentation, the patient did not complain of haematuria, fever, or flank pain. Abdominal and pelvic\nexaminations (transvaginal ultrasound) revealed no abnormal findings from female reproductive organs.\nThe estimated glomerular filtration rate was 69 mL/min/1.73 m\n2\n. Chest and abdominal CT with an IV\ncontrast agent was ordered.\nThe CT scan showed an anterolateral slightly enhanced mass on the left hypoplastic kidney measuring\n~1.2×1.1×0.9 cm (Figures \n1\n-\n2\n). The mass was positioned in the renal midline. The central region was\nmeasured at 23 Hounsfield units (HU) and was enhanced to 94 HU in the arterial phase. The lesion was\ncategorized as Bosniak IV, according to the Bosniak classification system of renal cystic masses \n[8]\n.\nFurthermore, CT did not reveal any pathological findings from the ovaries and uterus or evidence of\nabdominal and thoracic metastasis.\nFIGURE\n 1: Computed tomography axial view shows a slightly enhanced\nmass of 1.2 × 1.1 × 0.9 cm on the left hypoplastic kidney, positioned in\nthe renal midline (arrow).\n2024 Katsikatsos et al. Cureus 16(2): e55280. DOI 10.7759/cureus.55280\n2\n of \n7\n\nFIGURE\n 2: Computed tomography coronal view showing the mass on\nthe left hypoplastic kidney (arrow)\nA review of the diagnostic findings was presented at a multidisciplinary tumor board meeting. Treatment\noptions included renal biopsy and partial and radical nephrectomy. Given the radiological findings and\nimpaired function of the hypoplastic kidney, laparoscopic radical nephrectomy was recommended.\nA laparoscopic left radical nephrectomy was performed under general anesthesia. The patient was placed in\na modified flank position, and standard left-sided laparoscopic kidney port placement was performed \n[9]\n.\nThe nephrectomy was performed without major intraoperative complications, and the kidney was excised\nalong with Gerota’s fascia. The operation time was 128 minutes. The total blood loss was 133 cc. The\nspecimen was sent for pathologic analysis without being incised intraoperatively. Furthermore, there were\nno signs of endometriosis in the abdominal cavity during surgery.\nThe postoperative course was uneventful. On postoperative day one, the Foley catheter and redon drainage\ntube were removed. The patient was discharged on postoperative day two. Microscopic examination of the\nspecimen revealed multiple nodular foci of endometrial glandular and cystic formations lined by a single\ncell layer of columnar cells and surrounded by endometrial stroma (Figure \n3\n). Immunohistochemical\nevaluation revealed diffuse and strong nuclear positivity for hormonal receptors (ER and PR) in the benign\nendometrial glandular epithelium and patchy positive staining in the endometrial stroma (Figure \n4\n), while\nCD10 staining revealed focal cytoplasmic staining in endometrial stromal cells (Figure \n5\n). These\nmorphologic and immunophenotypic findings were consistent with a diagnosis of renal endometriosis.\nAccording to the findings, the patient was subjected to a follow-up protocol, which included a physical\nexamination and an abdominal ultrasound every six months for the first year. At her last visit, the patient\nremained free of symptoms.\n2024 Katsikatsos et al. Cureus 16(2): e55280. DOI 10.7759/cureus.55280\n3\n of \n7\n\nFIGURE\n 3: a) Benign endometrial-type glands and stroma adjacent to\nthe renal cortex (H/E x100). b) The benign endometrial type gland is\nlined by a single layer of columnar cells and endometrial stroma with a\nfine capillary network (H/E x200)\nFIGURE\n 4: a) Oestrogen receptor (ER) and b) progesterone Receptor\n(PR) show strong nuclear staining in endometrial stroma and patchy\npositive staining in benign endometrial glands (x100).\n2024 Katsikatsos et al. Cureus 16(2): e55280. DOI 10.7759/cureus.55280\n4\n of \n7\n\nFIGURE\n 5: Focal cytoplasmic CD10 staining in endometrial stromal cells\n(x100)\nDiscussion\nThe pathogenesis of extrapelvic endometriosis remains controversial, and several hypotheses, including the\nectopic transplantation theory, metaplasia of the coelomic epithelium, autoimmunity, blood lymphatic\nembolism, and the embryonic theory, have been proposed \n[10]\n. The ectopic transplantation theory, as\nproposed by Sampson in 1927, is generally accepted as the main cause of endometriosis \n[11]\n, but in some\ncases such as Mayer-Rokitansky-Kuster-Hauser syndrome, ovarian endometrioma, and peritoneal\nendometriosis, the coelomic metaplasia theory may be a suitable explanation \n[10-12]\n. In the coelomic\nmetaplasia theory, the coelomic epithelium undergoes metaplasia and forms endometrial stroma and glands\n[13]\n. The case reported here is difficult to explain by any specific theory.\nThe presence of genitourinary symptomatology depends on the extent, depth, and location of the ectopic\nendometrium. Symptoms include the typical triad of renal cell carcinoma (RCC) symptoms, lumbar pain,\ngross haematuria, and palpable lumbodorsal mass; thus, misdiagnosis can occur in many cases. One specific\ncharacteristic of renal endometriosis is repeated periodic pain and haematuria in parallel with the patient’s\nmenstrual cycles \n[14]\n. In this case, the patient did not present with any symptoms because the mass was\nsmall and confined to the renal cortex with no involvement of the calyces.\nThe diagnosis of endometriosis is often complicated by the lack of characteristic features on CT and\nmagnetic resonance imaging (MRI), as it shares many similarities with cystic malignancies \n[13]\n. According to\na literature review by Yang et al. \n[14]\n published in 2021, in 16 case reports of renal endometriosis, the\npreoperative diagnosis ranged from pyelonephritis, hematoma, and renal cyst to renal mass. Clinicians were\nunable to make a diagnosis in any of these cases without histopathology, revealing the difficulty in\nidentifying this rare entity purely with clinical and imaging criteria \n[13-30]\n. In our case, CT failed to\ndistinguish the lesion and showed slight enhancement in the central parts of the lesion. Renal endometriosis\nshould be suspected in young women of reproductive age with incidental masses who present with\nsymptoms that change during the menstrual cycle. In patients with a high clinical suspicion of renal\nendometriosis, a biopsy via fine-needle aspiration can be performed to alter treatment decisions, with the\npotential risk of tumor seeding via needle tracks \n[31]\n.\nClose active surveillance can be pursued in patients without symptoms diagnosed via biopsy \n[15]\n. For\nsymptomatic endometriosis, medical or surgical treatment is needed to alleviate symptoms. Medical\ntreatment seems to be the best option for patients of reproductive age and reduces pain. The agents that can\nbe used are oral contraceptives and GnRH agonists \n[20,23,26]\n. Definitive treatments for renal endometriosis\ninclude ablation or partial nephrectomy to alleviate symptoms \n[16]\n. In this case, the patient was\nasymptomatic, and thus, renal endometriosis was not suspected. Due to the high suspicion of renal tumor\non the CT scan and the hypoplastic left kidney with minimal participation in renal function, laparoscopic\nradical nephrectomy was proposed. Discriminating between a benign mass and a malignancy is difficult\n2024 Katsikatsos et al. Cureus 16(2): e55280. DOI 10.7759/cureus.55280\n5\n of \n7\n\nunless a nephrectomy is performed. A definitive diagnosis was made after the histopathological\nexamination, as in all the abovementioned cases.\nAfter surgical treatment, a follow-up protocol should be established. According to several cases of urinary\ntract endometriosis \n[32,33]\n, long-term surveillance with physical examination and abdominal ultrasound\nshould be pursued to evaluate symptom recurrence or anatomic relapse. In our case, we performed a\nphysical examination and abdominal ultrasound every six months for the first year and subsequently every\n12 months for the next two years.\nRenal endometriosis is a challenging diagnosis that should be suspected in women of childbearing age who\nexhibit symptoms that change with the menstrual cycle. Radiologic findings are not definitive in the\ndifferential diagnosis, and a biopsy should be performed if there is a high suspicion. Especially in cases of\nhematuria, a suspicion of urothelial carcinoma or a coexistence of RCC with urothelial carcinoma should be\nsuspected \n[34]\n. Nephron-sparing techniques, such as ablation and partial nephrectomy, should be performed\nin these patients, as most of these patients are young, and renal endometriosis is a benign disease.\nConclusions\nWe report the case of a woman who presented with a cystic mass in her left hypoplastic kidney that was\ndetermined to be renal endometriosis. As imaging fails to diagnose renal endometriosis effectively, the final\ndiagnosis requires histological confirmation. This case shows that renal endometriosis can mimic renal cell\ncarcinoma and awareness of this entity should be raised, as it can be asymptomatic, especially when located\non a hypoplastic kidney.\nAdditional Information\nAuthor Contributions\nAll authors have reviewed the final version to be published and agreed to be accountable for all aspects of the\nwork.\nConcept and design:\n  \nPanagiotis Katsikatsos, Konstantinos Douroumis, Dimitrios Goutas, Harikleia\nGakiopoulou, Ioannis Anastasiou\nAcquisition, analysis, or interpretation of data:\n  \nPanagiotis Katsikatsos, Konstantinos Douroumis,\nPeriklis Anastasiou\nDrafting of the manuscript:\n  \nPanagiotis Katsikatsos, Konstantinos Douroumis, Periklis Anastasiou\nCritical review of the manuscript for important intellectual content:\n  \nPanagiotis Katsikatsos,\nKonstantinos Douroumis, Dimitrios Goutas, Harikleia Gakiopoulou, Ioannis Anastasiou\nSupervision:\n  \nPanagiotis Katsikatsos, Ioannis Anastasiou\nDisclosures\nHuman subjects:\n Consent was obtained or waived by all participants in this study. \nConflicts of interest:\n In\ncompliance with the ICMJE uniform disclosure form, all authors declare the following: \nPayment/services\ninfo:\n All authors have declared that no financial support was received from any organization for the\nsubmitted work. \nFinancial relationships:\n All authors have declared that they have no financial\nrelationships at present or within the previous three years with any organizations that might have an\ninterest in the submitted work. \nOther relationships:\n All authors have declared that there are no other\nrelationships or activities that could appear to have influenced the submitted work.\nReferences\n1\n. \nMachairiotis N, Stylianaki A, Dryllis G, et al.: \nExtrapelvic endometriosis: A rare entity or an under diagnosed\ncondition?\n. Diagn Pathol. 2013, 8:194. \n10.1186/1746-1596-8-194\n2\n. \nSimoglou C, Zarogoulidis P, Machairiotis N, et al.: \nAbdominal wall endometrioma mimicking an\nincarcerated hernia: A case report\n. Int J Gen Med. 2012, 5:569-71. \n10.2147/IJGM.S32904\n3\n. \nAcién P, Velasco I: \nEndometriosis: A disease that remains enigmatic\n. ISRN Obstet Gynecol. 2013,\n2013:242149. \n10.1155/2013/242149\n4\n. \nGadelkareem RA, Mohammed N: \nUnilateral hypoplastic kidney in adults: An experience of a tertiary-level\nurology center\n. World J Nephrol. 2022, 11:30-8. \n10.5527/wjn.v11.i1.30\n5\n. \nZengin K, Tanik S, Sener NC, et al.: \nIncidence of renal carcinoma in non-functioning kidney due to renal\npelvic stone disease\n. Mol Clin Oncol. 2015, 3:941-3. \n10.3892/mco.2015.550\n6\n. \nVaudreuil L, Bessede T, Boissier R, et al.: \nDe novo renal carcinoma arising in non-functional kidney graft: A\nnational retrospective study\n. Int Urol Nephrol. 2020, 52:1235-41. \n10.1007/s11255-020-02422-0\n7\n. \nYeh CC, Lin TH, Wu HC, Chang CH, Chen CC, Chen WC: \nA high association of upper urinary tract\ntransitional cell carcinoma with nonfunctioning kidney caused by stone disease in Taiwan\n. Urol Int. 2007,\n2024 Katsikatsos et al. Cureus 16(2): e55280. DOI 10.7759/cureus.55280\n6\n of \n7\n\n79:19-23. \n10.1159/000102907\n8\n. \nde Miranda CM, Maranhão CP, Dos Santos CJ, Padilha IG, de Farias LPG, da Rocha MS: \nBosniak classification\nof renal cystic lesions according to multidetector computed tomography findings\n. Radiol Bras. 2014, 47:115-\n21. \n10.1590/S0100-39842014000200015\n9\n. \nJindal T, Mukherjee S, Koju R, S N, Phom D: \nSimplifying laparoscopic nephrectomy for beginners: Double\nwindow technique with en bloc hilar stapling\n. Cureus. 2021, 13:e16090. \n10.7759/cureus.16090\n10\n. \nSignorile PG, Baldi A: \nEndometriosis: New concepts in the pathogenesis\n. Int J Biochem Cell Biol. 2010,\n42:778-80. \n10.1016/j.biocel.2010.03.008\n11\n. \nKonrad L, Dietze R, Kudipudi PK, Horné F, Meinhold-Heerlein I: \nEndometriosis in MRKH cases as a proof for\nthe coelomic metaplasia hypothesis?\n. Reproduction. 2019, 158:R41-7. \n10.1530/REP-19-0106\n12\n. \nLamceva J, Uljanovs R, Strumfa I: \nThe main theories on the pathogenesis of endometriosis\n. Int J Mol Sci.\n2023, 24:4254. \n10.3390/ijms24054254\n13\n. \nSignorile PG, Baldi A, Viceconte R, Ronchi A, Montella M: \nPathogenesis of endometriosis: Focus on\nadenogenesis-related factors\n. In Vivo. 2023, 37:1922-30. \n10.21873/invivo.13288\n14\n. \nYang J, Song RJ, Xu C, Zhang SQ, Zhang W: \nRenal endometriosis tends to be misdiagnosed as renal tumor: A\nrare case report\n. Int Surg. 2015, 100:376-80. \n10.9738/INTSURG-D-13-00190.1\n15\n. \nYang Y, Zhao X, Huang Y: \nRenal endometriosis mimicking cystic renal tumor: Case report and literature\nreview\n. Front Med (Lausanne). 2021, 8:684474. \n10.3389/fmed.2021.684474\n16\n. \nGiambelluca D, Albano D, Giambelluca E, et al.: \nRenal endometriosis mimicking complicated cysts of\nkidney: Report of two cases\n. G Chir. 2017, 38:250-255.\n17\n. \nBadri AV, Jennings R, Patel P, Eun DD: \nRenal endometriosis: The case of an endometrial implant mimicking\na renal mass\n. J Endourol Case Rep. 2018, 4:176-8. \n10.1089/cren.2018.0070\n18\n. \nHajdu SI, Koss LG: \nEndometriosis of the kidney\n. Am J Obstet Gynecol. 1970, 106:314-315. \n10.1016/0002-\n9378(70)90284-x\n19\n. \nGauperaa T, Stalsberg H: \nRenal endometriosis. A case report\n. Scand J Urol Nephrol. 1977, 11:189-91.\n10.3109/00365597709179714\n20\n. \nBazaz-Malik G, Saraf V, Rana BS: \nEndometrioma of the kidney: Case report\n. J Urol. 1980, 123:422-423.\n10.1016/s0022-5347(17)55965-0\n21\n. \nHellberg D, Fors B, Bergqvist C: \nRenal endometriosis treated with a gonadotrophin releasing hormone\nagonist. Case report\n. Br J Obstet Gynaecol. 1991, 98:406-7. \n10.1111/j.1471-0528.1991.tb13434.x\n22\n. \nBenchekroun A, Nouini Y, Zennoud M, et al.: \nRenal endometriosis. Case report [Article in French]\n. Ann Urol.\n2001, 35:266-269. \n10.1016/s0003-4401(01)00041-9\n23\n. \nGupta K, Rajwanshi A, Srinivasan R: \nEndometriosis of the kidney: Diagnosis by fine-needle aspiration\ncytology\n. Diagn Cytopathol. 2005, 33:60-1. \n10.1002/dc.20228\n24\n. \nDutta P, Bhat MH, Bhansali A, Kumar V: \nA young woman with endometriosis of kidney\n. Saudi Med J. 2006,\n27:244-6.\n25\n. \nYaqub U, Hassan SE, Yusaf Z, Yusuf AW: \nEndometriosis in the renal area\n. J Coll Physicians Surg Pak. 2008,\n18:174-5.\n26\n. \nDirim A, Celikkaya S, Aygun C, Caylak B: \nRenal endometriosis presenting with a giant subcapsular\nhematoma: Case report\n. Fertil Steril. 2009, 92:391.e5-7. \n10.1016/j.fertnstert.2009.04.013\n27\n. \nJiang YH, Kuo HC, Hsu YH: \nRenal endometriosis mimicking an angiomyolipoma\n. Urol Sci. 2013, 24:24-26.\n10.1016/j.urols.2013.01.001\n28\n. \nCheng CH, Kuo HC, Su B: \nEndometriosis in a kidney with focal xanthogranulomatous pyelonephritis and a\nperinephric abscess\n. BMC Res Notes. 2015, 8:591. \n10.1186/s13104-015-1574-1\n29\n. \nUmair M, Nawaz M, Murtaza B, Ali A, Khan FB, Wahab AU: \nRenal endometriosis mimicking a renal tumor in\na pregnant patient\n. Urol Case Rep. 2020, 33:101374. \n10.1016/j.eucr.2020.101374\n30\n. \nBolze PA, Paparel P, Golfier F: \nUrinary tract involvement by endometriosis. Techniques and outcomes of\nsurgical management: CNGOF-HAS endometriosis guidelines [Article in French]\n. Gynecol Obstet Fertil\nSenol. 2018, 46:301-8. \n10.1016/j.gofs.2018.02.016\n31\n. \nMacklin PS, Sullivan ME, Tapping CR, et al.: \nTumour seeding in the tract of percutaneous renal tumour\nbiopsy: A report on seven cases from a UK tertiary referral centre\n. Eur Urol. 2019, 75:861-7.\n10.1016/j.eururo.2018.12.011\n32\n. \nSeracchioli R, Mabrouk M, Montanari G, Manuzzi L, Concetti S, Venturoli S: \nConservative laparoscopic\nmanagement of urinary tract endometriosis (UTE): Surgical outcome and long-term follow-up\n. Fertil Steril.\n2010, 94:856-61. \n10.1016/j.fertnstert.2009.04.019\n33\n. \nSaavalainen L, Heikinheimo O, Tiitinen A, Härkki P: \nDeep infiltrating endometriosis affecting the urinary\ntract-surgical treatment and fertility outcomes in 2004-2013\n. Gynecol Surg. 2016, 13:435-44.\n10.1007/s10397-016-0958-0\n34\n. \nSymeonidis A, Tsikopoulos I, Symeonidis EN, et al.: \nMore than meets the eye: A case of synchronous\nipsilateral clear cell renal cell carcinoma and urothelial carcinoma of the pelvicalyceal system and literature\nreview\n. Acta Biomed. 2022, 92:e2021380. \n10.23750/abm.v92i6.11768\n2024 Katsikatsos et al. Cureus 16(2): e55280. DOI 10.7759/cureus.55280\n7\n of \n7","source_license":"CC0","license_restricted":false}