Abstract
Background : Skeletal muscle metastasis from renal cell carcinoma (RCC) is rare. In this paper, we report a case of RCC with metastasis to the right brachial muscle diagnosed by fine needle aspiration cytology (FNAC).
Case : A male in his fifties who had undergone resection of a RCC 4 years previously presented to us with a swelling and pain in the right elbow. Magnetic resonance imaging revealed a mass in the right brachial muscle. FNAC revealed tumor cells that were scattered or formed irregular aggregates, had vacuolated cytoplasm and round to oval nuclei, and low nuclear to cytoplasmic ratios, but no marked irregular nuclear contours or conspicuous nucleoli. Histopathology of the resected mass revealed proliferating tumor cells with round to oval-shaped nucleoli and abundant clear cytoplasm, with necrosis. Moreover, immunocytochemical and immunohistochemical studies showed that the tumor cells were positive for AE1/AE3, vimentin, CD10 and PAX8. These findings were consistent with the morphological characteristics of the clear cell RCC resected 4 years previously. The final diagnosis was clear cell RCC with skeletal muscle metastasis.
Conclusion : Although cytology is not commonly performed for the diagnosis of RCC, it is important to recognize the cytological features of RCC in cases of RCC with metastasis.
