Thyroid-Like Follicular Carcinoma of the Kidney With Oncocytic Cells: A Case Report and Review of Metastatic and Non-metastatic Tumors

Abstract

Thyroid-like follicular carcinoma of kidney (TLFCK) is a morphological subtype of renal cell carcinoma, which is included as an emerging/provisional entity in the classification of renal tumors, with only about 40 cases reported in literature. It has a distinct histological appearance and immunohistochemical profile as compared with other renal cell cancers. However, these tumors, while appearing distinctive, have not been characterized fully either morphologically or by ancillary techniques. The reported cases show variable demographical and clinical features. Most are indolent, while some present with metastasis. The histological, immunohistochemical, and ultrastructural features of a case of TLFCK with clusters of oncocytic cells and pseudosarcomatous stroma are presented. Follow-up of 5 years was uneventful. A review of literature to analyze features in metastatic as compared with non-metastatic TLFCK is discussed. We report a patient of TLFCK and compare the clinicopathological features of metastatic and non-metastatic tumors.

Thyroid follicular renal cell carcinoma excluding thyroid metastases: A case report

“…However, considering that papillary thyroid carcinoma can develop lymph node or distant metastasis with very small primary foci, we believe that the first case of TFRCC was reported in an abstract published by Amin[ 4 ] in 2004 and in a case report published by Jung[ 5 ] in 2006. Thus far, approximately 41 cases have been reported[ 6 ].…”

“…TFRCC has a certain degree of invasiveness, up to T3, and can have retroperitoneal lymph node metastasis and distant metastasis such as skull and meninges[ 6 ]. These tumours may metastasise through the blood-derived pathway, but the degree of malignancy is generally low.…”

WHO 2022 landscape of papillary and chromophobe renal cell carcinoma

“…Thyroid-like follicular RCC is another phenotype already recognised for over a decade, 54 with <50 reported cases. 55 It may fall into the differential of pRCC, which often shows thyroid-like follicular areas filled with colloid material, 56 and may also mimic the so-called atrophic kidney-like lesion. 57 These tumours resemble thyroid follicular parenchyma, appear mostly in females, and show no expression of TGB or TTF-1 in the presence of PAX8 staining.…”

“…Thyroid‐like follicular RCC is another phenotype already recognised for over a decade, 54 with <50 reported cases 55 . It may fall into the differential of pRCC, which often shows thyroid‐like follicular areas filled with colloid material, 56 and may also mimic the so‐called atrophic kidney‐like lesion 57 .…”