Teratoid Wilms' tumor of kidney with neural tissue predominant: Case report with review of literature.

Wilms' tumor is most common pediatric renal tumor. Teratoid Wilms' tumor is a variant of Wilms' tumor, in which heterologous tissue predominates. Most commonly, epithelial and mesenchymal tissue present as heterologous component. Biological behavior of this tumor is very different from usual Wilms' tumor. They do not respond to chemotherapy and radiotherapy. We are presenting another case of teratoid Wilms' tumor in a 4-year female child with a review of literature. Copyright:

Introduction

Wilms’ tumor is the most common primary renal tumor of the pediatric age group. Histologically, it shows triphasic pattern of blastemal, stromal, and epithelial cell types.[1] The first case report of teratoid Wilms’ tumor was given by Variend et al. in 1984.[2] Later on, Fernandas et al. defined teratoid Wilms’ tumor in which heterologous component should be present at least 50% of tumor.[3] The heterologous component should be present in the form of adipose, muscle, cartilage, and glaial tissue. Beckwith further laid down criteria to define teratoid Wilms tumor, in which, he proposed that the tumor should lie entirely within the renal capsule and there should be a clear evidence of renal component and tumor tissue.[4] Until date, only 34 cases of teratoid Wilms tumor have been reported in English literature.[5] We are presenting another case of teratoid Wilms tumor, in a 4-year-old female child having neural tissue as predominant heterologous component through a review of literature.

Case Report

A 4 year female child presented with a complaint of having a right-sided abdominal mass since two months. This was palpable upon physical examination of the right lumbar area. Ultrasonography examination of the abdomen showed a large, sharply demarcated, and predominantly hyperechoic mass of 8 cm × 5 cm × 4 cm in the right paravertebral region of the normal kidney with areas of hypoechogenicity. No normal kidney tissue was identified on the right side. No calcification was noted. No intravascular echogenic focus was identified using a color Doppler sonography. The left kidney was normal in position and echo texture. A contrast-enhanced computed tomography (CT) scan showed heterogeneous mass in mid and lower pole of the right kidney and measured 8 × 5 × 4 cm in dimension. There was no enlargement of para-aortic lymph node (PAN). The preoperative routine investigations, including the serum urea, creatinine, and blood urea nitrogen were normal. Serum alpha fetoprotein levels were within normal limits. As a provisional diagnosis of the Wilms’ tumor, a right-sided nephrectomy was done and the specimen was sent for histopathological examination. On gross examination, the tumor measured 7 cm × 5 cm × 4 cm and was weighing 300 g. It was well-circumscribed and encapsulated. Cut sections presented homogenous gray white tumor tissue, which had a soft and granular texture [Figure 1]. Ureter and renal veins were free of tumor. Microscopically, multiple sections examined from different areas showed classic triphasic combination of blastemal, stromal, and epithelial cell types [Figure 2]. Histopathology did not show capsular invasion and vascular invasion. There was no anaplastic element. The heterologous elements are predominant and composed of ganglion cell as neural component, [Figure 3] and they constituted about 75% of the area from where the sections were examined. Considering the above histopathological features, a diagnosis of teratoid Wilms’ tumor was confirmed. The patient referred to the medical oncology department at a higher center. No postoperative chemotherapy was advised, considering the diagnosis of teratoid Wilms’ tumor. The patient was doing well 1-year post surgery. After that, the patient was lost to further follow-up.

Figure 1

Cut sections presented homogenous soft and granular textured gray white tumor tissue

Figure 2

Classic triphasic combination of blastemal, stromal, and epithelial cell types (×10)

Figure 3

The heterologous elements are predominant and composed of ganglion cell as neural component (×20)

Discussion

Wilms’ tumor is an embryonic tumor of mesodermal origin. This is the most common pediatric renal tumor and classically shows epithelial, mesenchymal, and blastemal components. Due to the totipotential nature of this tumor, sometimes, it shows different heterologous tissues in the form of skeletal muscle, smooth muscle, cartilage, bone, neural, and adipose tissue. Teratoid Wilms’ tumor is a rare variant of Wilms’ tumor. This entity was first described by Variend et al. in 1984,[2] Fernandes et al. further defined the teratoid Wilms’ tumor as triphasic tumor in which heterologous elements constituted more than 50% of the mass.[3] This tumor has been reported mainly in pediatric patients.[5] Literature search revealed 34 cases of teratoid Wilms’ tumor in children.[5] Till date, three cases of adult teratiod Wilms’ tumor have been reported.[6] Most cases, diagnosed between 2 to 4 years of age and six bilateral cases were observed. Raised Alfa-fetoprotein levels were reported in occasional cases.[7] In the present case, the tumor was unilateral and the opposite kidney was normal. The Alfa-fetoprotein levels were normal in the present case.

The most important differential diagnosis for teratoid Wilms’ tumor is intrarenal teratoma and metastasis from a germ cell tumor arising in another location or retroperitoneal teratomas secondarily invading the kidney. Although teratomas and teratoid Wilms’ tumor may have similar histology, teratomas display unequivocal organogenesis, such as stratified squamous epithelium associated with skin adnexa.[5] In the present case, both ovaries were normal and on histology, there was no attempt to organ formation like skin adnexa. In difficult cases, the WT1 gene was useful for confirmation.

Biological behavior of teratoid Wilms’ tumor is mostly nonaggressive with a favorable outcome. In comparison with classical Wilms tumor, the teratiod variant was reported to be resistant to chemotherapy and radiotherapy due to the well-differentiated nature of the teratomatous element.[8910] Hence, surgery is treatment of choice. However, in these cases, a few researchers recommended chemotherapy, regardless of tumor size, stage, age at diagnosis, and histological appearance. According to one of the case series report in literature, out of every 15 reported cases of teratoid Wilms’ tumor, chemotherapy was given in nine cases and only one case showed a cytoreductive response.[5] Due to mature teratoid element, there is resistance to chemotherapy. In the present case, tumor belonged to stage 1 category with favorable histology (lack of anaplasia). Tumor excised completely and postoperative chemotherapy was not given.

For teratoid Wilms’ tumor due to its rarity and heterologous element, there is no fix line of treatment. In these cases, further research should be carried out regarding the treatment protocol.

Conclusion

Teratoid Wilm's tumor of kidney is a rare entity, and this tumor shows resistance to chemotherapy due to its mature heterologous elements. It responds best to surgery. Hence, oncologists should avoid the use of chemotherapy in such patient to avoid unwanted complications of chemotherapy.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.