Symptomatic, Massive Right-Sided Splenic Heterotopia Masquerading as a Renal Cell Carcinoma With Metastasis

Heterotopic splenic tissue is a rare phenomenon that can occur in the abdomen and mimic renal or gastrointestinal tumors on imaging. We describe a 24-year-old woman who initially presented with right flank pain, urinary frequency, intermittency, and nocturia. The patient was found to have a large mass distorting and displacing the right kidney, thought to be renal cell carcinoma with concern for metastasis to the ileocecal junction based on radiographic imaging. The patient underwent right radical nephrectomy with right adrenalectomy and partial colon resection to remove the ileocecal mass. Pathological examination revealed the renal mass to be splenic tissue and the ileocecal mass to be a dermoid cyst, with no evidence of renal malignancy. This is an exceptional demonstration of a right-sided splenic heterotopia of remarkably large size sufficient to cause symptoms of a mass effect.