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CASE REPORT Table of Contents  
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Two case reports of mixed epithelial and stromal renal tumor of kidney in children and literature review analysis

1 Department of Pathology, Anhui Provincial Children's Hospital, Hefei, China
2 Department of Pathology, Children's Hospital of Fudan University, Shanghai, China

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Date of Submission09-Feb-2022
Date of Decision03-Mar-2022
Date of Acceptance04-Mar-2022
Date of Web Publication06-Jun-2022


Mixed epithelial and stromal tumor of the kidney (MESTK) occurs almost exclusively in perimenopausal women while rarely in children. Only five pediatric patients have been described previously. Herein, we report a girl and a boy with MESTK, aged 3- and 4-years-old, respectively. The two patients presented with hematuria or an abdominal mass. Histologically, the tumors were both composed of epithelial and stromal elements. Immunohistochemical staining of tumor cells expressed epithelial and mesenchymal component markers. They were diagnosed with MESTK by histology and immunohistochemistry after surgery. The patients were at good condition after surgery. To our knowledge, these are the youngest reported cases of MESTK. And the glandular luminal structure formed by the epithelium was lined with urothelium, which expanded the histological map of MESTK.

Keywords: Children, kidney, mixed epithelial and stromal tumor, pathology, urothelium

How to cite this URL:
Wei X, Wang Y, Fang Y, Chen L. Two case reports of mixed epithelial and stromal renal tumor of kidney in children and literature review analysis. Indian J Pathol Microbiol [Epub ahead of print] [cited 2023 Jan 29]. Available from:

   Introduction Top

Mixed epithelial and stromal tumor of the kidney (MESTK) is a biphasic benign tumor composed of a mixture of stromal and epithelial structures reported firstly in 1998 by Michal and Syrucek.[1] It mainly occurs in middle-aged and elderly woman, and almost all patients have a history of long-term use of estrogen.[2] To date, there are only five MESTKs in children reported previously. Herein, we described two Chinese children with such a rare condition.

   Case Report Top

Patient 1 is a 3-year-old girl. The patient was admitted to a local hospital for hematuria. A mass was palpated in the upper left abdomen with a hard texture, clear boundaries, no tenderness, and poor mobility during physical examination. Laboratory examinations except for routine urine were all normal. A computed tomography (CT) imaging scan of the abdomen showed a huge well-circumscribed heterogeneous solid mass in the left kidney, measuring 6.0 × 9.4 × 10.2 cm [Figure 1]a. Patient 2 is a 4-year-old boy. The patient was admitted to a Children's Hospital of Fudan University for abdominal mass. His left abdomen was obviously swollen. Laboratory examination showed no significant abnormalities. CT revealed a huge and heterogeneous mass behind the left retroperitoneum, about 13.7 × 8.3 × 16.9 cm in size [Figure 1]b. No evidence of distant metastasis was present in both the patients.
Figure 1: (a and b) Abdominal CT scans showed a heterogeneous solid mass in the left kidney in both the patients

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As a consultation case for patient 1, the gross appearance of the tumor was not available. Microscopically, the tumor was composed of both epithelial and stromal elements. Stromal components were mainly comprised of non-specific spindle cells with invisible mitotic. The epithelium formed glandular cavity-like structure dispersed in the stromal, which was lined by the urothelium [Figure 2]a. Immunohistochemical staining of the epithelial component demonstrated reactions to cytokeratin (CK). Spindle cells were positive for vimentin, smooth muscle actin (SMA), muscle-specific actin (MSA), estrogen receptors (ER) [Figure 2]b, and negative for progesterone receptors (PR) [Figure 2]c. Ki-67 labeling index was 10%. The NTRK3 gene rearrangement was negative. Ultimately, the patient was diagnosed with MESTK.
Figure 2: (a) The tumor is composed of a mixture of epithelial and stromal components. The epithelium formed glandular cavity-like structure lined by the urothelium and the stroma is made up of spindle cells (HE × 100). (b) The tumor cells were positive for ER (IHC × 100). (c) The tumor cells were negative for PR (IHC × 100)

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For patient 2, the huge tumor was gray, sallow, and tough [Figure 3]a and [Figure 3]b. Microscopically, the tumor was mainly composed of spindle cells with flakelike and nodular distribution and some areas appeared epithelioid with renal tubule-like structures [Figure 3]c. Spindle cells in the stromal components expressed vimentin, desmin, SMA, and ER, but were not immunoreactive for PR. Ki-67 labeling index was 5%. The diagnosis of MESTK was established.
Figure 3: (a) Gross appearance of the tumor. (b) Section view of the tumor. (c) The tumor is mainly composed of stromal components and some areas appeared epithelioid with renal tubule-like structures (HE × 100)

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Both the patients had no history of abdominal surgery, trauma, estrogen use, or congenital defects. The two patients underwent surgery. Patient 1 received left radical nephrectomy and patient 2 underwent left nephron sparing surgery. The tumors were completely removed. The two patients were free of disease in 3–6 months after tumor excision and long-term follow-up was continued till now.

   Discussion Top

MESTK is a distinct renal neoplasm that develops from the mÜllerian-like stromal cells and occurs primarily in perimenopausal women, accounting for 0.2% of all renal tumors.[2],[3] MESTK is uncommon in children, with only five cases reported [Table 1].[3],[4],[5],[6],[7] MESTK mainly occurs in children before puberty (8–12 years old), and there is no significant difference between gender. Abdominal mass, abdominal pain, hematuria, and proteinuria are the common clinical manifestations. The age of the onset of tumor for the two patients we reported, 3- and 4-years–old, respectively, was younger than that reported in the literature. The clinical manifestations in our cases were hematuria or abdominal mass.
Table 1: Clinical data of five patients with MESTK

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Histologically, the vast majority of MESTK show benign morphological features and are usually composed of epithelial and stromal components. Stromal components were composed of bundles of spindle cells with various degrees of smooth muscle fibroblast/myofibroblast differentiation. Epithelium is scattered within the stroma and consisted of glandular lumen structures with or without cystic dilation. Glandular lumens are usually lined with flat or cubic epithelium. Nuclear mitosis, hemorrhage, and necrosis are rare in benign MESTK. For immunohistochemical staining, epithelial cells express CK, and spindle cells are positive for vimentin, desmin, SMA. Estrogen receptors have high expression in spindle cell nuclei while expression of PR is inconsistent. The histological morphology of patient 1 in this study was also consisted of epithelium elements and stroma components composed of spindle cells. But the glandular lumens that made up the epithelial components were lined by urothelial rather than flat or cubic epithelium. For patient 2, the tumor was mainly composed of stroma components, and the epithelial components were not obvious. The histological morphology of the two MESTK cases described in this paper was not as typical as that reported in the previous literature. Therefore, it is somewhat difficult for our pathologists to establish an exact diagnose.

The pathogenesis of MESTK is yet not clear in children. Long-term estrogen replacement therapy or exposure to the environment and the high expression of tumor sex hormone receptors may play an important role in the pathogenesis of MESTK in adults.[8] The two patients in this paper and those in the reported literature had no sexual hormone exposure history before onset. Therefore, it is speculated that the pathogenesis of MESTK in children is different from that in adults, and may not be closely related to the exposure of estrogen progesterone. The exact pathogenesis remains to be studied.

MESTK is a benign tumor, and most patients can survive for long term after surgical resection. Relapse and malignant transformation have been reported in adults and chemotherapy should be given when there is evidence of lymph node or distant metastasis.[9] Regular follow-up is essential to assess the long-term prognosis of patients, especially those who cannot undergo tumor resection.

   Conclusion Top

MESTK is infrequent in children. The two patients we reported were the youngest in the literature. Moreover, special note was made of urothelium lining the glandular luminal structure, which expands the histological map of MESTK in children. Although not common, MESTK should be considered as the differential diagnosis of renal tumors in children.

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.

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Conflicts of interest

There are no conflicts of interest.

   References Top

Michal M, Syrucek M. Benign mixed epithelial and stromal tumor of the kidney. Pathol Res Pract 1998;194:445-8.  Back to cited text no. 1
Caliò A, Eble JN, Grignon DJ, Delahunt B. Mixed epithelial and stromal tumor of the kidney: A clinicopathologic study of 53 cases. Am J Surg Pathol 2016;40:1538-49.  Back to cited text no. 2
Ferdjallah A, Gordon P, Kirankumar V, Dietz K, Bu L, Verghese P. Mixed epithelial and stromal tumor after pediatric kidney transplant. Pediatr Transplant 2019;23:e13575.  Back to cited text no. 3
Hara N, Kawaguchi M, Murayama S, Maruyama R, Tanikawa T, Takahashi K. Mixed epithelial and stromal tumor of the kidney in a 12-year-old girl. Pathol Int. 2005;55:670-6.  Back to cited text no. 4
Teklali Y, Piolat C, Durand C, Boillot B, Pasquier D, Jacquier C, et al. Mixed epithelial and stromal renal tumour in a 12-year-old boy. J Pediatr Urol 2010;6:320-3.  Back to cited text no. 5
Goszczyk A, Straz-Zebrowska E, Jung A. Kidney tumor in 12-year-old girl case study of the rare histopatologic form of neoplasm in children. Pol Merkur Lekarski 2008;24:10-11.  Back to cited text no. 6
Vergine G, Drudi F, Spreafico F, Barbisan F, Brachi S, Collini P, et al. Mixed epithelial and stromal tumor of kidney: An exceptional renal neoplasm in an 8-year-old prepubertal girl with isolated clitoral hypertrophy. Pediatr Hematol Oncol 2012;29:89-91.  Back to cited text no. 7
Mohanty SK, Parwani AV. Mixed epithelial and stromal tumors of the kidney: An overview. Arch Pathol Lab Med 2009;133:1483-6.  Back to cited text no. 8
Holkar PS, Jain T, Kavishwar V, Pandya JS. Metastasis in mixed epithelial stromal tumour of the kidney: A rare presentation. BMJ Case Rep 2019;12:e229293.  Back to cited text no. 9

Correspondence Address:
Lian Chen,
Department of Pathology, Children's Hospital of Fudan University, 399 Wanyuan Road, Shanghai - 201102
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/ijpm.ijpm_148_22


  [Figure 1], [Figure 2], [Figure 3]

  [Table 1]


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