Clinicopathologic characteristics of thyroid-like follicular carcinoma of the kidney: an analysis of five cases and review of literature

Abstract

Objective: To study the clinicopathologic features of thyroid-like follicular renal cell carcinoma. Methods: Clinical data were collected in 5 cases of thyroid-like follicular renal cell carcinoma. HE staining and immunohistochemistry were carried out in surgically-removed specimen to analyze the clinical and pathological features with review of the literatures. Results: The patients aged 20-55 years, with one male and four females; the tumor occurred in the left kidney in three cases and right kidney in two cases. One case had a history of thyroid papillary carcinoma 3 years ago, and the patient had left flank pain, macroscopic haematuria for 2 weeks. The rest four cases had no consciousness of clinical symptoms and signs, without history of thyroid gland surgery; the physical examination found a mass in the kidney and normal thyroid glands. Three patients underwent radical nephrectomy, and the other two patients underwent tumor partial nephrectomy. The tumors were 2-4 cm in size. They showed a solitary nodular mass of well circumscribed with taupe and gray on cut surface. Microscopically, most of tumor cells arranged in thyroid follicular pattern in different sizes, with papillary configuration in a small portion, in four cases; the follicular structure was intermixed with the papillary each half in one case. A large amount of thyroid colloid was deposited within follicule-like structure or papillary axis, lined by simple columnar cells or cubic cells, with obvious atypia, ground-glass nuclei, nuclear groove and rare mitosis. Immunohistochemical staining showed tumor cells were positive for PAX8, and negative for thyroid transcription factor 1 (TTF1) and thyroglobulin (Tg). One of five patients presented with lymph node metastases (4/4) of renal hilum the same time in the diagnosis. Five cases were followed up for 5-84 months after operation, and no tumor progression was found. Conclusions: Thyroid-like follicular renal cell carcinoma is primary renal epithelial malignant tumor. The diagnosis mainly depends on its characteristics of histological appearance, namely similar to the histological morphology of well-differentiated thyroid follicular carcinoma and papillary carcinoma, and the metastasis from the thyroid papillary or follicular carcinoma must be excluded. On the premise of clinical history, immunohistochemical markers TTF1 and Tg have certain value in the differential diagnosis.