Mixed epithelial and stromal tumor (MEST) in a young adult male: A case report and literature review

Introduction and importance: A MEST is a rare renal tumor, with stromal as well as epithelial components. It is predominantly benign and local recurrence is not very common. In the majority of the cases, it occurs in females. Its occurrence in a young male makes it a rarity. Case presentation: A 24 years old male presented at SIUT with the complaint of left flank pain on and off for one month. CT scan showed soft tissue density mass in left renal pelvis extending from mid-pole calyces to pelviuretric junction, leading to obstruction and ultimately mild uropathy. We found a partially obstructing staghorn calculus with asymmetrical cortical thinning. Left Robot-Assisted Nephro-ureterectomy plus excision of bladder cuff was planned in which 3 x 4 cm mass involving the left renal pelvis was excised. To date, there is no radiologic evidence of disease recurrence. Clinical discussion: MEST in young adults is an extremely rare tumor. They have been referred to by many alternate synonyms including 'adult mesoblastic nephroma' and 'cystic nephroma' with 'ovarian' or 'cellular' type stroma. Majority of patients with MEST present, with hematuria, abdominal pain, palpable flank mass, recurrent urinary tract infections. Similarly, our patient presented initially with nonspecific pain in the left flank region. Majority of cases in the literature presented with the tumor in benign stage, with localized spread, and without recurrence. Conclusion: Mixed epithelial and stromal tumors (MEST) of the kidney are distinct entities of benign kidney tumors. MEST in young males is a very rare entity, and a small number of cases exist. Histopathology plays a very cardinal role in diagnosis, and overall the disease has a promising outcome with conservative surgery.