Acquired cystic disease (ACD)-associated renal cell carcinoma (RCC) has recently been established. Herein we report the sixth case of ACD-associated RCC with a sarcomatoid change. The patient was a 77-year-old man who regularly underwent hemodialysis for 14 years due to chronic renal failure resulting from IgA nephropathy. On computed tomography, a large right RCC was observed with contrast enhancement in the arterial phase. A nodular protrusion into the perirenal fat was detected. Right nephrectomy was performed under laparoscopy. Surgically resected specimens revealed a tan-to-yellow tumor (95 × 75 × 55 mm) with a whitish nodule (20 × 15 × 15 mm) invading into the perirenal fat. Histopathologically, the large carcinoma component of the tumor displayed a cribriform or microcystic growth pattern with deposition of oxalate crystals. The whitish nodule corresponded to the sarcomatoid component, and the spindled and pleomorphic tumor cells showed diffuse positivity of p53 on immunohistochemistry. Fluorescence in situ hybridization revealed trisomy of chromosomes 3 and 16 in the carcinoma component, as was expected from the literature. In addition, increased polysomy of these chromosomes was also observed in the sarcomatoid component. This finding may be related to the development of the sarcomatoid component along with the TP53 mutation.

A 49-year-old female presented with an aggressive pelvic angiomyxoma (AAM). The completely resected specimen revealed the usual myxedematous tumor with a nodule inside it. Histopathologically, the myxedematous area consisted of bland spindle-shaped cells in the background of blood vessels of varying calibers, and the nodule was composed of tumor cells with epithelioid features. In the nodule, cellularity was increased and nuclear enlargement was observed, but nuclear atypia was not significant and mitotic figures were scarce. Immunohistochemically, both components were positive for desim, αSMA, estrogen receptors, and progesterone receptors. However, they were negative for AE1/3, EMA, S100, CD34, HMB45, and Melan A. The MIB-1 labeling index was 5.8% in the nodule and 1ess than 1% outside it. The nodule was therefore considered a benign component of AAM. To the best of our knowledge, the presence of such a nodule in AAM has not been reported previously.