Unusual presentation of mixed epithelial and stromal tumor of ureter posing diagnostic dilemma

Gaurvi Piplani; Kishan H L. Prasad; K Sajitha; TP Rajeev; Shubha Bhat; Suraj Hegde

doi:10.4103/UROS.UROS_69_20

CASE REPORT

Year : 2021 | Volume : 32 | Issue : 2 | Page : 89-92

Unusual presentation of mixed epithelial and stromal tumor of ureter posing diagnostic dilemma

Gaurvi Piplani¹, Kishan H L. Prasad¹, K Sajitha¹, TP Rajeev², Shubha Bhat¹, Suraj Hegde²
¹ Department of Pathology, K S Hegde Medical Academy of Nitte (Deemed to be University), Mangaluru, Karnataka, India
² Department of Urology, K S Hegde Medical Academy of Nitte (Deemed to be University), Mangaluru, Karnataka, India

Date of Submission	24-Apr-2020
Date of Decision	26-Jul-2020
Date of Acceptance	13-Aug-2020
Date of Web Publication	22-Jun-2021

Correspondence Address:
Kishan H L. Prasad
Department of Pathology, K S Hegde Medical Academy of Nitte (Deemed to be University), Mangaluru - 575 018, Karnataka
India

Source of Support: None, Conflict of Interest: None

DOI: 10.4103/UROS.UROS_69_20

Abstract

The mixed epithelial and stromal tumor (MEST) family comprises a spectrum of tumors varying from predominantly cystic tumors such as adult cystic nephroma, to variably solid tumors such as MESTs. These rare renal tumors typically affect women in their perimenopausal age. Most of these tumors are benign; however, at some rare occasions, they are associated with malignant transformation. The current article reports a rare case of MEST arising from the proximal ureter in a perimenopausal woman, manifested as a cord-like structure in the ureter, and posing the diagnostic dilemma.

How to cite this article:
Piplani G, L. Prasad KH, Sajitha K, Rajeev T P, Bhat S, Hegde S. Unusual presentation of mixed epithelial and stromal tumor of ureter posing diagnostic dilemma. Urol Sci 2021;32:89-92

How to cite this URL:
Piplani G, L. Prasad KH, Sajitha K, Rajeev T P, Bhat S, Hegde S. Unusual presentation of mixed epithelial and stromal tumor of ureter posing diagnostic dilemma. Urol Sci [serial online] 2021 [cited 2022 Sep 25];32:89-92. Available from: https://www.e-urol-sci.com/text.asp?2021/32/2/89/318999

Introduction

Mixed epithelial and stromal tumor (MEST) is a very rare benign adult renal tumor that contains biphasic epithelial and stromal components with spindle stroma, glands, and cysts.^[1] This tumor typically affects perimenopausal women, with a female-to-male ratio of 7:1.^[1],[2],[3] Patients usually present with hematuria, flank pain, abdominal or flank mass, and urinary tract infection-like symptoms.^{[1],[2],[3],[4],[5]} These tumors involve the medulla, bulging into the renal pelvis or centered within the renal pelvis or the cortex and the medulla.^[1],[5] Microscopically, they contain biphasic epithelial and stromal components with spindle stroma with glands and cysts.^[1],[2] Smooth muscle and lipomatous metaplasia are rarely seen.^[1] Malignant transformation rarely occurs.^[1] The current article reports an unusual case of MEST arising from the proximal ureter in a 50-year-old female with a cord-like extension in the ureter, posing diagnostic dilemma.

Case report

A 50-year-old female presented with right-sided loin pain for 6 months. There was no palpable abdominal mass. An X-ray kidney, ureter, and bladder showed ill-defined renal shadows without any abnormal calcific densities. Ultrasonography of the abdomen and pelvis showed an endophytic, pedunculated enhancing lesion in the posterior wall of the urinary bladder with extension to the lower two-third of the right ureter, likely suggestive of urothelial carcinoma with contracted right kidney and hydroureteronephrosis. Magnetic resonance imaging (MRI) of the pelvis showed heterogeneously enhancing intensity lesion arising from the posterior wall of the urinary bladder in the right paramedian region with extension into the lower two-third of the right ureter, suggestive of a malignant growth, likely urothelial carcinoma [as illustrated in [Figure 1]. Her routine hematological, biochemical, and microbiological findings were unremarkable. Urine cytology was unexceptional. Hence, diagnostic cystoscopy was done, which showed a cord-like growth arising from the right renal pelvis/proximal ureter extending up to the bladder opening. The patient underwent right radical nephroureterectomy with bladder cuff incision. On gross examination, a shrunken right kidney along with a dilated ureter and polypoidal growth with bladder cuff was noted. The cut surface of the kidney showed a dilated pelvicalyceal system filled with hemorrhage and thinned cortex at the periphery. The cut surface of the ureter showed a dilated lumen, with the middle and distal portions of the ureter showing pale white, cylindrical, endophytic growth measuring 16 cm in length, which is a continuation of the polypoidal growth seen on the outer surface [as shown in [Figure 2]a. Histopathology of the growth showed an ulcerated surface with residual urothelium with leaf-like pattern with cystitis cystica changes and focal squamous metaplasia [as shown in [Figure 2]b and [Figure 2]c]. At places, epithelial cells were arranged in nests and focal tubules. Some of the tubules were cystically dilated. The stroma appeared loose and fibromyxoid [as demonstrated in [Figure 2]d]. The bladder cuff showed a thickened wall with an ulcerated epithelium, and the ureter showed a thinned wall with an attenuated epithelium. The right kidney showed hydronephrotic changes and chronic pyelonephritis. Extensive sampling revealed no evidence of malignancy in any of the tissue studied. Immunohistochemistry was performed which showed cytokeratin positivity in the overlying epithelium, and the stroma showed immunoreactivity for vimentin, estrogen receptor (ER), and desmin and weak positivity for progesterone receptor (PR) [as illustrated in [Figure 3]a, [Figure 3]b, [Figure 3]c, [Figure 3]b, [Figure 3]e. Hence, the final diagnosis of a MEST of the proximal ureter with tumor extension to the distal ureter and chronic pyelonephritis with hydroureteronephrosis of the right kidney was made. She was closely followed up and was doing well in her last visit.

Figure 1: Magnetic resonance imaging pelvis showing endophytic growth in the ureter with polypoidal projections in the bladder (shown in the arrow)

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Figure 2: (a) Gross specimen showing cord-like exophytic growth in the ureter extending up to the bladder cuff with shrunken right kidney. (b) Histopathology showing tumor with leaf-like growth pattern with ulcerated epithelium (H and E, ×100). (c) Histopathology showing cystitis cystica areas lined by urothelium (H and E, ×100). (d) Histopathology showing loose fibromyxoid stroma with surface epithelium (H and E, ×100)

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Figure 3: Immunohistochemistry showing CK positivity in the overlying mucosa (a), stroma with immunoreactivity for vimentin (b), estrogen receptor (c), progesterone receptor (d), and desmin (e)

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Discussion

The MEST family comprises a wide range of tumors varying from predominantly cystic tumors such as adult cystic nephroma, to variably solid tumors such as MESTs.^[1],[6] They are usually unilateral and typically affect perimenopausal women with an age of 52 years approximately.^[1],[5],[7] Patients typically present with hematuria, flank pain, abdominal or flank mass, and urinary tract infection-like symptoms. MEST occurring in renal pelvis/proximal ureter is extremely rare.^[1],[2],[5] The current article reports the case of a 50-year-old female who presented with right-sided loin pain for 6 months.

The MEST does not have any definite criteria for diagnosis on imaging by computed tomography/MRI.^[2] About 70% of these tumors have a solid enhancing component along with thick- or thin-walled multiseptate cystic masses.^[1],[4],[5] In the current case, ultrasonography of the abdomen and pelvis showed an endophytic, pedunculated enhancing lesion in the posterior wall of the urinary bladder with extension to the lower two-third of the right ureter. MRI of the pelvis showed heterogeneously enhancing intensity lesion arising from the posterior wall of the urinary bladder in the right paramedian region with extension into the lower two-third of the right ureter, suggestive of malignant growth, likely transitioned cell carcinoma.

The diagnostic cystoscopy showed the lesion arising from the right renal pelvis/proximal ureter with a cord-like structure in the ureter extending to the bladder as polypoid-like projections. These tumors on gross examination appear as solitary, unencapsulated, and rarely well circumscribed and have a mean size of 9 cm.^[1] These tumors involve the medulla and display variable proportions of solid and cystic components.^[1],[6] In our patient on gross examination, a shrunken right kidney along with a dilated ureter and polypoidal growth with bladder cuff was noted. Cut surface of the ureter showed a dilated lumen and the middle and distal portions of the ureter contained pale white, cylindrical cord-like endophytic growth measuring 16 cm in length, which is a continuation of the polypoidal growth seen on the outer surface. This is a very unusual manifestation of MEST.

Microscopically, they show biphasic epithelial and stromal components with spindle stroma with glands and cysts.^[1],[2] These cysts or glands are lined by flat-to-cuboidal, hobnail, columnar cells, which have eosinophilic, vacuolated cytoplasm along with focal mullerian features such as endometrioid and tubal appearance or rarely pyloric/intestinal or urothelium.^[1],[5],[6] The stroma is hypocellular and collagenous to markedly cellular, often with ovarian-type stroma having secondary luteinization.^[1],[3] Rarely, smooth muscle or lipomatous metaplasia is seen. Cytological atypia is rare.^[1] Malignant transformation is rarely seen, with morphology resembling stromal sarcoma, carcinosarcoma, chondrosarcoma, or rhabdomyosarcoma.^[1],[3] In our case, it showed a tumor with urothelium in nests and tubules, with few of them showing cystic dilatation. The stroma appeared loose and fibromyxoid. The adjacent kidney showed hydronephrotic changes and chronic pyelonephritis.

The differential diagnosis to be considered in such cases is cystitis cystica et glandularis (CCEG) and benign fibroepithelial polyp. CCEG rarely presents with a cord-like structure which shows several glands lined by columnar or cuboidal cells and surrounded by urothelial cells without cytological atypia within the lining of the glands. The stroma will be loose with mixed inflammatory cells. Benign fibroepithelial polyp presents with polypoid growth in the ureter, with histology showing loose fibrous tissue, blood vessels, and chronic inflammatory infiltrates with focal surface epithelium.^[8],[9]

Immunohistochemistry is rarely needed in these cases, which shows that the stromal component is typically positive for actin, desmin, CD10, ER, and PR. The ovarian-type stroma may express inhibin and calretinin.^[1],[6] The current case also showed similar immunohistochemistry findings as described above.

Treatment of choice is surgical excision. It is necessary to rule out other differential diagnosis and rare cases with malignant transformation.^[4] In our case, right radical nephroureterectomy with bladder cuff incision was done. The local recurrence will be seen in cases of incomplete resection.^[4],[7] In our case, after 6 months of follow-up, the patient is doing well.

Conclusion

MEST is a benign and rare tumor of the kidney, which predominately affects perimenopausal women usually involving the medulla. However, tumor arising from the proximal ureter/renal pelvis as a cord-like structure is extremely rare as seen in the current case. Such atypical presentations can lead to the diagnostic dilemma; thus, providing more detailed knowledge regarding this rare tumor is helpful for proper management.

Declaration of patient consent

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

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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