Cytologic diagnosis of thyroid‐like follicular carcinoma of the kidney: A case report

Abstract

Thyroid-like follicular carcinoma of the kidney (TLFCK) is a recently described subtype of renal-cell carcinoma that is not currently included in the World Health Organization classification. Few sporadic case reports and one series have been reported with emphasis on histopathologic features. However, cytological features have not been described in the literature to date. A 34-year-old male presented with a renal mass. An intraoperative smear preparation of the tumor revealed a hypercellular smear with cells arranged in sheets without any follicular, papillary, or acinar arrangement. The most striking feature was the presence of acellular eosinophilic material associated with the neoplastic epithelial cells in the background of the smear. Individual tumor cells were oval, round, and plasmacytoid with mild nuclear pleomorphism, finely stippled nuclear chromatin, and inconspicuous nucleoli with moderate amount of eosinophilic cytoplasm and rare nuclear grooves. It was unclear at the time of the intraoperative assessment of the smear if the acellular eosinophilic material represented metachromatic matrix-like extracellular material, mucin, colloid, amyloid, or hyaline material. The differential diagnoses included a primary renal-cell carcinoma versus a metastatic tumor. Subsequent histopathologic examination was diagnostic of a rare, recently described primary neoplasm of the kidney called TLFCK. This work is a retrospective evaluation of the cytological features of TLFCK. It is important for cytopathologists to be aware of this entity and its cytological features to render a correct diagnosis for adequate management of these patients.

Thyroid-like follicular carcinoma of the kidney in a patient with nephrolithiasis and polycystic kidney disease: a case report

“…In FNAB, focal calcifications were additionally noted on top of some fragments, which was not the case in histological samples, where they were absent. Analogous to our case, nuclear grooves in FNAB of TFLC have been noted by Dhillon et al [11]. The authors retrospectively described FNAB results after already publishing histologic and clinical characteristics of the same TFLC, unique for the presence of lung and retroperitoneal lymph nodes metastases [8].…”

The International Society of Urological Pathology (ISUP) Vancouver Classification of Renal Neoplasia

“…[82][83][84][85][86][87] Macroscopically, these tumors are well circumscribed, solid, and generally homogenous tanbrown in color. In the fewer than 15 cases reported in the literature, the age range is wide (29 to 83 y), and there is a slight female predominance.…”

Thyroid-like follicular carcinoma of the kidney: A Case report

“…The diagnosis of TLFCK mainly depends on the microscopic appearance and immunohistochemical experience. Morphologically, TLFCK consists of different sized follicular structures containing abundant eosinophilic colloid resembling to the well-differentiated follicular thyroid carcinoma, as a comparison, TLFCK show a obviously different morphological features from other types of renal carcinoma [6]. Immunohistocemically, TLFCK has a typical negative performance of thyroid immunohistochemical markers, like thyroid transcription factor-1(TTF1) and thyroglobulin(TG), respectively, the staining of CD10 and CK17 is variable [1,3,5,7].…”

“…TLFCK is a kind rare pathological type of renal tumor, which is potentially considered origining in the renal parenchymal urinary tubule epithelial system [1]. This unique histopathological type of RCC(renal cell carcinoma), described firstly in 1996 by Angell et al, had not been recorded in the 2004 world health organization in account of the lack of sufficient clinical evidence that only 28 cases reported in the English literature to date [2][3][4][5][6][7][8][9][10][11][12][13][14][15]. TLFCK has a similar feature with the follicular carcinoma of the thyroid in morphology.…”