Case Study

A rare presentation of bilateral synchronous renal tumours misdiagnosed as tuberculosis

Debi M. Moagi, Busiswa F. Bisiwe

Received: 02 Sept. 2024; Accepted: 20 Jan. 2025; Published: 28 Feb. 2025

Copyright: © 2025. The Author(s). Licensee: AOSIS.
This is an Open Access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

A 32-year-old woman with dialysis-requiring kidney failure presented with constitutional symptoms and bilateral kidney masses and was initially diagnosed with renal tuberculosis (TB). However, despite TB treatment, her condition deteriorated, leading to a right nephrectomy. Histopathological examination revealed the presence of embryonal rhabdomyosarcoma (ERMS), a rare malignancy typically seen in paediatric populations. Alternative diagnoses, even rare ones like ERMS, should be considered when dealing with bilateral kidney masses. Radical nephrectomy remains the primary treatment for ERMS, but adjuvant therapies may also be beneficial.

Contribution: This case highlights the diagnostic challenges of bilateral kidney masses and the importance of considering rare malignancies in the differential diagnosis. Prompt histopathological evaluation is crucial for accurate diagnosis and timely management.

Keywords: kidney masses; tuberculosis; embryonal rhabdomyosarcoma; misdiagnosis; diagnostic challenges.

Introduction

Kidney masses are a common clinical finding, which can present unilaterally or bilaterally.¹ The presence of bilateral multifocal kidney masses on imaging often proves to be a diagnostic and therapeutic dilemma.¹ Renal malignancies as a cause of bilateral kidney masses are rare, occurring in less than 5% of the population.²

Rhabdomyosarcoma (RMS) is an aggressive soft tissue tumour that arises from muscle progenitor cells.³ It is the most common soft tissue sarcoma in paediatric patients and is very rare in adults, often presenting late and with metastases.⁴ Sarcomas of the kidney are found in approximately 1% of all primary renal malignancies in adults.³ They have been studied mainly in the paediatric population. Thus, there are currently no well-established treatment guidelines in the adult population. However, the literature suggests that adults with RMS have a worse clinical outcome compared to the paediatric population.³

This case report presents an intriguing case of embryonal rhabdomyosarcoma (ERMS) of the kidneys in an adult patient, highlighting the complexities involved in diagnosis and management.

Case presentation

A 32-year-old woman of African descent was referred to a tertiary nephrology unit with dialysis-requiring kidney failure for further management. She was found to have been previously healthy without a family history of kidney disease and now presented with insidious onset of constitutional symptoms with low-grade fever, unintentional weight loss and vomiting coffee-ground material for about a week.

On clinical examination, the patient was apyrexial, hypertensive, tachycardic and pale with bilateral pitting oedema. Abdominal examination revealed bilateral palpable renal masses. On laboratory investigation, she was found to be anaemic with an elevated C-reactive protein of 53 mg/L and an erythrocyte sedimentation rate (ESR) of > 90 mm/h. She was in kidney failure with a urea of 22.1 mmol/L and creatinine of 1112 µmol/L, corresponding to an estimated glomerular filtration rate (eGFR) of 3 mL/min per 1.73 m². Auto-immune and viral studies were negative. Urine cultured Escherichia coli.

Computed tomography (CT) of the abdomen and pelvis revealed enlarged kidneys with distorted architecture, bilateral dilated renal pelvises and calyces with dystrophic calcifications in the upper pole of the left kidney and multiple para-aortic pathological lymph nodes (Figure 1a and Figure 1b).

FIGURE 1: (a) Axial computed tomography (CT) scan of abdomen and pelvis demonstrates bilateral massively dilated renal pelvises and calyces, right larger than left, with mixed density fluid within the calyces suggestive of haemorrhage (white arrows). (b) Non-contrasted axial CT scan of abdomen and pelvis demonstrating pathological lymph nodes (white arrow). (c) Axial CT chest scan demonstrating bilateral pleural effusions (black arrows) and bilateral lower lobe ground glass opacities (red arrows).

A provisional diagnosis of renal tuberculosis (TB) was made based on the constitutional symptoms, elevated ESR and CT findings. Tuberculosis treatment with rifampicin, isoniazid, pyrazinamide, and ethambutol was initiated empirically while awaiting TB culture results.

Despite the TB treatment, the patient continued to deteriorate further. She developed frank haematuria and right flank pain associated with increased transfusion requirements. She subsequently underwent a right nephrectomy for persistent macro-haematuria.

Histopathological examination of the right kidney revealed a tumour measuring 128 × 115 × 69 mm, with large areas of necrosis and haemorrhage. There were sheets and nodules of highly pleomorphic round-to-spindle cells with apoptotic bodies and atypical mitotic figures. The tumour involved the renal sinus and hilum, with no lympho-vascular invasion. The tumour was present on the inferior capsular surgical margin. Immunohistochemistry showed positive staining for myogenin, desmin, BCL-2 and weakly positive FLI-1 gene expression but was negative for CKAE1/3, EMA, S-100, CD34, CD99 and WT-1. These findings were in keeping with ERMS. After 42 days of incubation, mycobacterium cultures were reported to be negative.

On staging CT scan, the aorta and inferior vena cava (IVC) appeared normal. There was retroperitoneal adenopathy, multiple thyroid nodules, a lytic lesion in the L1 spinous process and bilateral pleural effusions (see Figure 1C). Diagnostic pleurocentesis revealed an exudative effusion with no malignant cells on cytologic examination. The tumour was therefore classified as a stage 4, T2b, N1, M1 clinically. It is assumed that the left kidney has the same disease as it appears similar on imaging, and a left nephrectomy is planned for the near future.

Discussion

The causes of kidney failure with bilaterally enlarged kidneys include inherited causes such as autosomal dominant polycystic kidney disease (ADPKD), tuberous sclerosis complex, malignancies and infections.¹ Genitourinary TB may mimic many of the above-mentioned causes of renal masses. Symptoms and signs are often non-specific and may overlap across the various diagnoses. It may present asymptomatic or with haematuria, sterile pyuria, flank pain, abdominal masses, renal abscesses and, granulomas and chronic kidney disease (CKD).⁵ While urine culture is the gold standard for diagnosing genitourinary TB, nucleic acid amplification tests (NAATs) and GeneXpert MTB/RIF assays have high sensitivity and specificity of > 90%, and they provide results quicker than TB culture, which requires at least 42 days of incubation.⁶ In this case, the high TB prevalence in South Africa influenced the initial diagnostic pathway. However, the absence of microbiological confirmation of TB and the atypical imaging findings should have prompted consideration of alternative diagnoses earlier.

Rhabdomyosarcoma is commonly present in children, particularly in the head, neck and genitourinary tract. Genitourinary tract tumours often involve the bladder and other pelvic organs and rarely involve the kidneys.^4,5 The RMSs in adults occur rarely and are usually quite aggressive. Rhabdomyosarcoma can be classified into alveolar, embryonal, spindle-cell and pleomorphic.⁷ Botryoid is a subtype of ERMS.⁴ The clinical and imaging findings of ERMS can resemble those of renal cell carcinoma (RCC), thus making the distinction between the two conditions difficult.^4,7

Advances in imaging using CT and MRI have improved the ability to differentiate between benign and malignant causes of cystic renal masses and have demonstrated a high ability to diagnose renal cell carcinoma and other tumours.⁸ While CT imaging suggested TB, its limitations in distinguishing between inflammatory and malignant processes were evident. In patients with multiple or bilateral kidney masses without a history of familial renal neoplastic syndromes and atypical imaging findings, kidney biopsy can be used to help establish diagnosis and exclude benign causes.⁸ Expert radiological review and early biopsy could have expedited the correct diagnosis, avoiding unnecessary TB treatment. Limited access to CT-guided biopsy in our setting further compounded the problem. This highlights the importance of integrating histopathological evaluation in atypical presentations.

The diagnosis of ERMS is confirmed histopathologically. Immunohistochemistry aids in diagnosis, with myogenin and MyoD1 positivity being specific for RMS.^4,7 The CD-99 negativity and patchy FLI-1 positivity made the diagnosis of Ewing’s sarcoma unlikely. Immunohistochemical staining, in this case, confirmed the diagnosis while excluding other entities such as Ewing’s sarcoma and Wilms tumour.

Treatment of kidney ERMS is generally the same as ERMS that occurs elsewhere in the body. Radical nephrectomy remains the mainstay of therapy. However, emerging evidence suggests that adjuvant chemotherapy and radiotherapy may play a role.^4,7

Conclusion

Bilateral kidney masses often pose a diagnostic and therapeutic challenge in practice. Rhabdomyosarcoma, a rare but aggressive tumour, should be considered in the differential diagnosis, especially when other conditions such as RCC or TB are suspected. Tuberculosis is an endemic disease in Africa, and clinicians need to be wary of its extra-pulmonary manifestations. This case demonstrates that imaging alone is insufficient to distinguish between malignant and benign causes of renal masses, and microbiological evidence of TB should be sought to avoid missing other causes of renal masses. Histopathological examination remains the gold standard for confirming the diagnosis of most kidney diseases, particularly in complex clinical pictures that do not fit a specific disease process. Furthermore, the case underscores the pitfalls of anchoring diagnoses to endemic diseases without sufficient evidence. It highlights the need for a systematic approach integrating radiological expertise, biopsy, and histopathology to avoid misdiagnosis. Delays in diagnosis can have serious consequences, especially in patients with rare and potentially malignant conditions.

Acknowledgements

The authors would like to thank the patient for their trust and for allowing them to share her case. They also acknowledge Johan Botes for his assistance in finalising and submitting this article.

The authors declare that they have no financial or personal relationships that may have inappropriately influenced them in writing this article.

D.M.M. and B.F.B. were involved in all stages of this case, from patient management to article preparation.

Ethical clearance to conduct this study was obtained from the University of the Free State and Health Sciences Research Ethics Committee (reference no.: UFS-HSD2024/0145/2603). Written informed consent was obtained from the patient involved in this case study.

This research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.

The data that support the findings of this study are available from the corresponding author, D.M.M., upon reasonable request.

The views and opinions expressed in this article are those of the authors and are the product of professional research. The article does not necessarily reflect the official policy or position of any affiliated institution, funder, agency, or that of the publisher. The authors are responsible for this article’s results, findings, and content.

References