Indian Journal of Pathology and Microbiology

: 2021  |  Volume : 64  |  Issue : 4  |  Page : 866--867

Urothelial carcinoma with divergent differentiation in a horseshoe kidney

B Madhumitha1, Leena Dennis Joseph1, B Archana1, T Chandru2,  
1 Department of Pathology, Sri Ramachandra Institute of Higher Education and Research, Chennai, Tamil Nadu, India
2 Department of Urology, Sri Ramachandra Institute of Higher Education and Research, Chennai, Tamil Nadu, India

Correspondence Address:
B Archana
Department of Pathology, Sri Ramachandra Medical College, Porur, Chennai - 600 116, Tamil Nadu

How to cite this article:
Madhumitha B, Joseph LD, Archana B, Chandru T. Urothelial carcinoma with divergent differentiation in a horseshoe kidney.Indian J Pathol Microbiol 2021;64:866-867

How to cite this URL:
Madhumitha B, Joseph LD, Archana B, Chandru T. Urothelial carcinoma with divergent differentiation in a horseshoe kidney. Indian J Pathol Microbiol [serial online] 2021 [cited 2023 Feb 1 ];64:866-867
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Dear Editor,

Horse shoe kidney is the most common congenital renal fusion anomaly affecting 1 in 400 live births.[1] Tumors that arise here are associated with predisposing factors such as infection, stones and obstruction. Most common malignancy reported in the horse shoe kidney is renal cell carcinoma. Urothelial carcinoma usually arises in the renal pelvis. However, the same in the isthmus of a horseshoe kidney is a very uncommon finding. Moreover, most of the reported cases have a pure urothelial component, tumors with divergent differentiation is rarer. Of great clinical significance is the fact that diagnosis is made at advanced stages and problems may arise during surgery due to altered anatomy and aberrant blood supply. We report a case of a 60-year-old male with primary urothelial carcinoma with divergent differentiation, arising in a horse shoe kidney.

A 60-year-old male, known case of horse shoe kidney anomaly came with complaints of painless hematuria in the Urology outpatient department. The patient had a history of diabetes and systemic hypertension and was on regular medications. Laboratory data were within normal limits except for urinary analysis which revealed 20-30 Red Blood cells (RBC) per high power field. Urine for Cytology showed clusters of epithelial cells with nuclear atypia and pleomorphism [Figure 1]a and was reported as suspicious for malignancy. Renal ultrasound revealed a horse shoe kidney, but the lesion could not be picked up. CT urogram showed a horse shoe kidney with relatively well defined heterogeneously enhancing lesion in the isthmus with moderate perilesional and perinephric fat stranding [Figure 1]b. Prominent uniformly enhancing lymph nodes were noted in bilateral para-aortic, pre and retro caval regions. PET CT was done for evaluation of primary and metastatic workup, which revealed focal FDG avid lesion in the isthmus extending to bilateral lower poles and right mid pole [Figure 1]c suggesting possibly a malignancy. Open right nephrectomy was done and sent for histopathological examination. Gross examination of the specimen weighed 400 g and showed a tumor in the region of the isthmus extending to the upper pole measuring 8/5/4 cms, which was solid, firm and gray white in color [Figure 1]d. Microscopic examination of the tumor showed areas of classic urothelial carcinoma (pathological staging-pT3Nx), with urothelial component (20%), glandular differentiation (60%) and squamous differentiation (20%) [Figure 2]a, [Figure 2]b, [Figure 2]c, [Figure 2]d. Margins were involved by the tumor. Immunohistochemistry (IHC) was done which showed positivity for GATA3, p63, vimentin and CK7 [Figure 3]a, [Figure 3]b, [Figure 3]c, [Figure 3]d. IHC for CK20 and PAX8 were negative. This pattern confirmed our diagnosis of urothelial carcinoma with divergent differentiation. The background kidney showed hypertensive arteriosclerosis in the blood vessels. Glomeruli appeared normal. The patient also underwent cystoscopy to rule out urothelial carcinoma in the bladder, which turned out to be negative. Post-operatively, serum creatinine and blood urea nitrogen values were normal.{Figure 1}{Figure 2}{Figure 3}

Subsequently the patient was subjected to post-operative chemotherapy in view of the margin positivity. He withstood 6 cycles of chemotherapy and currently is on follow-up since 6 months.

Tumors arising in a horse shoe kidney are relatively rare. Blackard et al. has described 72 cases of malignant tumors in a background of horse shoe kidney.[2] Tijani et al. reported a case of clear cell carcinoma in a horse shoe kidney.[3] The incidence of urothelial carcinoma in a horse shoe kidney is approximately 3 to 4 times than in a normal kidney, possibly the result of chronic obstruction, lithiasis and infection which are common predisposing factors in the horse shoe kidney. Frequently anomalous vascular supply creates an obstacle to renal pelvic drainage leading to stasis and calculus formation.[4]

In the index case, the patient had renal calculi which probably caused urinary stasis, chronic irritation and subsequent urothelial carcinoma.

Most urothelial tumors that arose in a horse shoe kidney had pure urothelial histology, only rare cases with divergent differentiation have been reported. Among those with divergent differentiation, squamous and glandular differentiation are the most common. Others such as trophoblastic differentiation, microcystic, micropapillary, lymphoepithelioma-like, plasmacytoid/signet ring cell/diffuse, sarcomatoid, giant cell, lipid-rich, clear cell (glycogen-rich) have also been described. Each differentiation has its own unique clinical, pathological and molecular features. Compared to pure high grade urothelial carcinomas, those with divergent differentiation were associated with aggressive disease.[5] Other tumors that are seen in a horseshoe kidney are carcinoid, clear cell variant of renal cell carcinoma and squamous cell carcinoma. The anatomy of the isthmus and major blood vessels is complicated in patients with horse shoe kidney, thus posing a challenge to the surgeon.

Thus, urothelial carcinoma with divergent variation in a horseshoe kidney is associated with a higher stage, lympho-vascular and perineural invasion indicating a poor prognosis. Hence an extensive search for divergent differentiation in urothelial carcinoma should be done by the pathologist as these factors may be associated with adverse clinical outcomes and requires optimal planning for further management.

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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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