Fibromyxoid Nephrogenic Adenoma Mimicking Renal Cell Carcinoma: A Diagnostic Pitfall in Fine-Needle Aspiration Cytology.
Jodi Gedallovich, Adebola Adeniyi, Ankur R Sangoi et al.
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Case in brief
A 72-year-old man presented with a right renal mass, evaluated due to a history of nephrolithiasis. Fine-needle aspiration cytology revealed cloudy red fluid with scant epithelial cells, leading to a pre-operative diagnosis of renal cell carcinoma based on immunohistochemical findings. However, partial nephrectomy revealed a unilocular cyst with fibromyxoid stroma and spindled cells, ultimately diagnosed as fibromyxoid nephrogenic adenoma.
What made this case unusual
The fibromyxoid variant of nephrogenic adenoma closely mimicked renal cell carcinoma both cytologically and immunohistochemically, presenting significant diagnostic challenges.
Diagnostic / clinical pearl
Clinicians should be aware that fibromyxoid nephrogenic adenoma can mimic renal cell carcinoma, particularly in fine-needle aspiration samples, necessitating careful interpretation of cytologic and immunohistochemical findings.
Why it matters
This case highlights the importance of recognizing the cytologic features of fibromyxoid nephrogenic adenoma to prevent misdiagnosis and avoid unnecessary surgical interventions.