Thyroid-Like Follicular Renal Cell Carcinoma Treated by Laparoscopic Partial Nephrectomy: Two Cases and a Literature Review

Thyroid-like follicular renal cell carcinoma (TLF-RCC) is a rare renal neoplasm that can mimic metastatic thyroid carcinoma, requiring careful clinicopathologic correlation and immunohistochemistry to confirm diagnosis. We report two incidental renal masses treated with laparoscopic partial nephrectomy. Case 1 was a 46-year-old woman with a small enhancing renal lesion. Histology showed thyroid-like follicles filled with eosinophilic colloid-like material. Immunohistochemistry supported renal origin (PAX8 positive) and excluded thyroid origin (thyroglobulin and TTF-1 negative). She had an uncomplicated postoperative course with no evidence of recurrence at 6 months. Case 2 was a 56-year-old man with an incidentally discovered enhancing renal mass. Pathology demonstrated TLF-RCC with focal perirenal fat invasion and a positive surgical margin. Immunohistochemistry similarly excluded thyroid primary. He recovered uneventfully and remained disease-free at 12 months. No perioperative complications occurred. Follow-up imaging showed no recurrence or metastasis at 6 and 12 months, respectively. TLF-RCC is a distinct and uncommon renal tumor with important differential diagnostic considerations. Correlation with thyroid evaluation and a focused immunohistochemical panel is essential to exclude metastatic thyroid carcinoma. Given limited evidence on optimal surveillance, follow-up may be individualized using risk-adapted renal cell carcinoma principles, particularly in patients with adverse pathologic features.