Large Retroperitoneal Teratoma Presenting with Unilateral Hydronephrosis in an Infant: A Case Report and Review of the Literature

Teratoma is a type of germ cell tumor containing an embryonic germ cell layer that appears in the gonadal and sacrococcygeal, mediastinal, intracranial, cervical, and retroperitoneal regions [1]. Primary retroperitoneal teratoma is rare, accounting for 4% of all primary teratomas, and is usually asymptomatic [2, 3]. However, in some cases, it can present with different symptoms based on the mass pressure effect on neighboring organs. Because of this mass effect of tumors in patients with teratoma, there is a risk of urologic comorbidities, such as bladder dysfunction or hydronephrosis [4]. These types of germ cell tumors may be cystic or solid, mature or immature, or mixed germ cell tumors [5, 6].

Retroperitoneal cystic immature teratoma rarely occurs in children (less than one percent of all childhood tumors) and is histopathologically composed of mainly immature neural tissue [7]. These tumors be an issue in the differential diagnosis of a mass in the abdominal cavity of children to distinguish between Wilms’ tumor, neuroblastoma, and other intra-abdominal lesions [8]. Here, we will discuss a rare case of huge retroperitoneal immature teratoma in a 6-month-old infant that presented with abdominal mass and hydronephrosis. The CARE Checklist has been completed by the authors for this case report, attached as supplementary material, available online at https://doi.org/10.1159/000533829.

The patient was a 6-month and 29-day old boy without any significant past medical disease who presented with irritation and protrusion of the left upper quadrant of the abdomen. Also, an abdominal mass was palpated by his mother, which had progressively become enlarged. So, the patient was referred to a pediatrician, and abdominopelvic ultrasonography was requested. Abdominopelvic ultrasonography showed hydronephrosis of the left kidney due to the pressure effect of a large septate cystic lesion (91 × 72 mm) without a solid part on the left side of the abdomen. He was referred to our hospital for further evaluation.

He was afebrile with stable vital signs during the physical examination. In the abdominal examination, a left-sided abdominal mass was palpated. Laboratory data showed elevated C-reactive protein and erythrocyte sedimentation rate (C-reactive protein = 67 mg/dL, erythrocyte sedimentation rate = 21 mm/h) and mild leukocytosis (white blood cells = 13,000 per μL). The kidney function tests, such as blood urea nitrogen and creatinine, were in the reference range, and the urine analysis showed alkaline urine with a specific gravity of 1.005.

An abdominal computed tomography (CT) scan revealed a large cystic, solid mass (90 × 88 × 118 mm) on the left side of the abdominal cavity arising from the retroperitoneum causing anterior deviation of the pancreas and lateral deviation of the left kidney. The mass caused pressure on the left ureter, and moderate hydronephrosis of the left kidney was seen with a decreased enhancement of the left kidney due to obstruction uropathy. Also, internal calcification and fat density in the lesion were seen. The mass was reported to be in favor of retroperitoneal teratoma. Besides, the left adrenal gland could not be delineated because of the pressure effect of the mentioned mass. The deviation of the abdominal aorta to the right side was also present due to the mass (shown in Fig. 1).

The patient underwent exploratory laparotomy, and excision of the huge retroperitoneal mass was done. Intraoperative findings showed a solid cystic mass on the left side of the abdominal cavity from the upper to lower quadrant with transposition of the small bowel, large bowel, and major vessels to the right side. However, the left ureter and left kidney were transposed to the posterolateral, leading to hydronephrosis (shown in Fig. 2).

An oval mass with a size of 12 × 8 × 7.5 cm was received in the macroscopic examination. The external surface was bosselated and creamy pink in color. Cut sections showed multicystic areas filled with clear fluid, mucinous material, and some nodularity and bony areas (shown in Fig. 3). The final diagnosis was an immature teratoma grade 3 (20% of teratoma composed of immature elements).

The patient was discharged in good condition 6 days after the surgery with suspensions of cefixime and metronidazole. The patient was visited at our clinic postoperatively 1 week later, with no signs and symptoms presented. Also, the patient was referred to a pediatric hematologist-oncologist for possible chemotherapy sessions. The pediatric hematologist-oncologist evaluated the patient following the operation. After performing chest and abdominopelvic CT scans, whole-body bone scans, and laboratory factors, including alpha-fetoprotein and beta-human chorionic gonadotropin, and consultation with the patient’s parents, it was decided that the patient could be followed with routine imaging and laboratory data (with no need for chemotherapy) due to no sign of metastasis and normal imaging and laboratory factors. The patient had been visited in an outpatient setting every 4 months in the first year of post-operation, and, currently, he is being followed every 6 months as we are in the second year of the follow-up (current follow-up: 1.5 years). The patient is well with no signs and symptoms or metastasis/recurrence.

The most common type of germ cell tumor is teratoma, divided into three types: mature, immature (or malignant type), and monodermal. The mature type of teratoma is the most common type, which is a benign solid or cystic tumor [9]. While most teratomas are present in the gonadal region, the extragonadal teratomas are in the sacrococcygeal area, mediastinum, intracranial, and retroperitoneal area. Retroperitoneal teratomas, after Wilms tumor and neuroblastoma, are the most common retroperitoneal tumors in children accounting for about 3.4–4% of all germ cell tumors in children. About 4–6% of all teratomas are primary retroperitoneal teratomas, usually occurring in the suprarenal area and are more commonly present on the left side [10]. One of the problems of these tumors is differentiating them from Wilms tumors and neuroblastomas or other intra-abdominal tumors [8]. Our case describes a giant immature retroperitoneal teratoma, which is rare in this size in children under 1 year of age. Besides, this tumor was large enough to lead to a mass effect on the left ureter in a way that the patient developed hydronephrosis.

Teratoma in children usually has no specific characteristic signs or symptoms. There are different clinical presentations based on the size and location of the tumor, but their main presentation is abdominal distension or a palpable abdominal mass [11]. To the best of our literature search, there are only a few cases of retroperitoneal teratoma in children, large enough to cause hydronephrosis by the pressure effect of the mass [12‒15] (Table 1). In our case, the tumor had a pressure effect on the internal organs and caused a lateral deviation of the left kidney and pressure on the left ureter, so the patient developed moderate left hydronephrosis. Also, the enhancement of the left kidney decreased due to obstruction uropathy of tumor effect. Of note, while the previous cases of retroperitoneal teratoma causing hydronephrosis were mostly mature teratomas (Table 1), our case had an immature teratoma grade 3.

Wilms and neuroblastoma are the most important differential diagnosis of retroperitoneal teratoma. Also, they can be mistaken for ovarian and adrenal tumors, renal cysts, or sarcomas [16]. However, most retroperitoneal teratomas have typical radiological features. CT and magnetic resonance imaging are reliable modalities that show the tumor and vessels well. CT is the most reliable imaging modality for diagnosing and evaluating retroperitoneal teratomas. A large complex mass with well-defined cystic components, fat, and areas of calcification represents the typical radiologic CT appearance of a teratoma [10]. In our case, before further evaluation and because of hydronephrosis reported in the ultrasonography, we suspected Wilms tumor and performed a CT scan, which plays an important role in diagnosing retroperitoneal teratoma. By CT scan and histopathologic diagnosis after resection, the definite diagnosis of teratoma was taken, and an immature teratoma grade 3 was diagnosed in our case.

In conclusion, retroperitoneal teratomas are rare tumors in infants that are generally asymptomatic and can be found incidentally or due to the mass effect of the huge tumors on the other organs. However, they should be considered as a differential diagnosis of intra-abdominal tumors in children. Hydronephrosis and obstructive uropathy can be rare consequences of the mass effect of teratomas resulting from very large-sized masses. Our case highlights two important issues.

• 1. Although immature retroperitoneal teratoma under 1 year of age is rare, it should be considered as a differential diagnosis of retroperitoneal masses in this age group.

• 2. This mass can be large enough to cause obstructive uropathy and hydronephrosis.

This retrospective review of patient data did not require ethical approval in accordance with local/national guidelines. Written informed consent was obtained from the patient’s parents for publication of this case report and any accompanying images. A copy of the written consent is available for review by the editor of this journal.

The authors have no conflicts of interest to declare.

The study was not funded.

M.F. performed the surgery, supervised the work, and contributed to data gathering. N.S. drafted the manuscript and contributed to data gathering. H.K. contributed to data gathering and revising the manuscript. M.H.A. provided the pathology images. O.R.Z. and M.B. contributed to revising the manuscript. All authors have read and approved the final version of the work.

All data generated or analyzed during this study are included in this article. Further inquiries can be directed to the corresponding author.