Primary cilia are hair-like organelles singly distributed along the apical surface of proximal and distal nephron tubules as mechanosensors. The goal of this study was to use electron microscopy to systemically evaluate cilia changes in acute tubular injury (ATI) from both transplant and native renal biopsies. Three groups of cases were included: control group 1-native biopsies without major changes in renal tubules; study group 2-native biopsies with prominent ATI; and study group 3-renal transplant biopsies with prominent ATI (delayed renal function group). Extensive search for ciliary structures along renal tubules was conducted in each case, focused on proximal tubular areas with injured (diminished) apical microvilli. Singly located cilia were found in 3/19 specimens in control group 1, 4/18 in group 2 (native ATI), and 6/24 in group 3 (transplant ATI). Importantly, there were clusters of cilia in proximal tubules with markedly diminished apical microvilli in 3/24 biopsies from 2 patients in group 3, but none from groups 1 and 2. The clusters of cilia ranged from 6 to 15 individual cilia along the apical surface with diminished apical microvilli. Under high magnifications, the cilia demonstrated 9 pairs of peripheral microtubules without a central pair of microtubules, consistent with primary cilia (9 + 0) rather than motile cilia (9 + 2). In summary, the authors found clusters of cilia in proximal tubules with remarkable apical microvillar injury in 3 renal transplant biopsies with ATI, implying a reactive, or repairing, process following tubular injury, thus they name this finding "cilia metaplasia".
Synchronous occurrence of dual pathology is known to occur, but triple pathology in the kidney is an extraordinarily rare phenomenon. Our unique case showed incidental triple pathologies in the same kidney. A left nephroureterectomy specimen received in our anatomic pathology department revealed a high-grade papillary urothelial carcinoma, cystic clear cell carcinoma, and multiple nodules of papillary renal cell carcinoma of unknown malignant potential (former papillary renal cell carcinoma, according to size criteria of 0.5-2.0 cm, WHO classification). A 61-year-old man came to the urology department. His medical history was significant for smoking, hypertension, sleep apnea, and coronary heart disease. No family history or genetic history was given in his chart. Gross examination revealed the kidney weighed 220 g and measured 15 × 7 × 5 cm. Serial sectioning of the specimen revealed a single papillary lesion in the renal pelvis measuring 5 × 5 × 3 cm without any areas of hemorrhage or necrosis. Incidental findings covering the entire surface of kidney included multiple cystic and solid golden yellow nodules ranging from 1 to 12 mm. Microscopic examination showed a high-grade papillary urothelial carcinoma, cystic clear cell carcinoma, and papillary neoplasm of uncertain malignant potential (former papillary renal cell carcinoma). Additional findings included multiple renal cell papillomatosis, cortical cysts, and arterial arteriosclerosis. Immunohistochemistry showed positive staining for CD10 and p63 and negativity for P504S. Our case is unique in that 3 distinct pathologies were present in the same kidney. we have not come across any literature describing multiple entities including high-grade papillary urothelial carcinoma, cystic clear cell carcinoma, papillary renal cell carcinoma, cortical cysts, and other chronic changes in 1 kidney. This unusual constellation of papillary renal neoplasms raises the question of genomic alterations.
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