Papillary adenoma of the kidney with mucinous secretion

Although infrequently, mucin secretion has previously been reported in papi llary renal cell carcinoma. We here investigate the presence of mucin in a series of 93 renal papillary adenomas in 58 patients. Acid mucin was presen t in four cases (4.3% of the tumors; 6.9% of the patients), in which basoph ilic mucin secretion was evident with hematoxylin-eosin. To the best of our knowledge mucin secretion has not been reported in renal papillary adenoma . We describe two different types of mucin secretion: intracytoplasmic and luminal. The secretion was intracellular in numerous scattered tumor cells in two cases, focal luminal in one case, and mixed intracellular and lumina l in another case. Mucin production, despite its low frequency, can be cons idered as an additional feature of renal papillary adenoma. Mucin productio n suggests that renal papillary adenoma and papillary renal cell carcinoma are actually not two independent biological processes, but a continuum of o ne biological process.