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SOLITARY METASTASIS OF RENAL CLEAR CELL CARCINOMA TO H ÜRTHLE CELL ADENOMA OF THYROID GLAND: REPORT OF A CASE. RITA PASSANTINO - LORENZO MARASA’ Department of Pathology, A.R.N.A.S. Civico, Palermo. INTRODUCTION.
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SOLITARY METASTASIS OF RENAL CLEAR CELL CARCINOMA TO HÜRTHLE CELL ADENOMA OF THYROID GLAND: REPORT OF A CASE RITA PASSANTINO - LORENZO MARASA’ Department of Pathology, A.R.N.A.S. Civico, Palermo
INTRODUCTION • Metastases to the thyroid gland are a common finding at autopsy in patients who died of malignancy and are often misdiagnosed as primary thyroid neoplasms clinically. • Metastatic Renal Cell Carcinoma (RCC) to the thyroid gland is a rare occurence but must be considered in the differential diagnosis of Clear Cell Tumours (CCT) of the thyroid gland to prevent misclassification, potentially resulting in inappropriate clinical management. • We present a patient with a rare, unusual case of RCC metastatic to a Hürthle cell adenoma of the thyroid gland.
CASE REPORT • The patient was a 77-year-old sicilian woman who was referred to our department after a thyroid tumour was identified in February 2008. • She had a history of RCC of the left kidney, which had been resected 3 years previously. • Ultrasound sonography demonstrated a well-demarcated hypoechoic mass which measured 3.5 cm in greatest diameter and occupied the left lobe. • A total thyroidectomy was performed on March 2008. • A solitary, well circumscribed, encapsulated, bright yellow to reddish-tan mass with hemorrhage and degenerative changes, which measured 3.5 cm in greatest diameter and occupied the left lobe of the thyroid gland.
HISTOLOGICAL EXAMINATION • A Hürthle cell adenoma containing large clusters of cells with abundant clear cytoplasm and round nuclei. • The predominant histologic pattern was characterized by the presence of small nests, cords and “pseudofollicles” made up of neoplastic cells separated by a prominent vascular stroma with sinusoidal-type blood vessels and intraluminal fresh hemorrhage. • Metastatic cells contained variable amounts of PAS-positive material which was indicative of glycogen in the cytoplasm of the clear cells. • Metastasis showed morphological characteristics identical to the RCC resected 3 years previously.
IMMUNOHISTOCHEMICAL EXAMINATION • Specific markers of Hürthle cell adenoma such as thyroglobulin, CK14, CEA, S-100 protein and HMB-45 stained negatively in the clear neoplastic cells. • Specific markers of RCC such as EMA and vimentin stained positively. THYROGLOBULIN EMA VIMENTIN
CONCLUSIONS • The thyroid gland is a rare site of tumour metastasis. • RCC is one of the more common neoplasm to metastasize to the thyroid gland (<0.1%). • Metastatic RCC to a thyroid neoplasm is extremely rare, with only three reports found in the international literature. • The possibility of metastatic RCC should always be taken under consideration, especially when nests of clear cells are seen infiltrating into the thyroid parenchyma or neoplasm.
CONCLUSIONS • Our report shows that the architectural, cytologic, hi-stologic, histochemical, and immunohistochemical fea-tures are sufficiently distinctive to allow differentation of a primary thyroid epithelial neoplasm with clear cell changes from metastatic RCC. • This distinction is important to correctly manage the patient. • Surgical treatment is recommended as the patient may enjoy a prolonged survival. MAIN REFERENCE: Qian L. Renal cell carcinoma metastatic to Hürthle cell adenoma of thyroid. Ann Diagn Pathol. 2004 Oct; 8(5): 305-8.