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Pathology - Non-malignant kidney neoplasms
Papillary adenoma • Benign renal epithelial neoplasm exhibiting a papillary or tubulopapillary structure, measuring 5mm or less. • Commonly identified accidentally in nephrectomy specimens or during autopsy. Macroscopically, they are well-defined cortical nodules measuring 5 mm or smaller. Histologically, they consist of non-atypical epithelial cells exhibiting papillary or tubulopapillary arrangements.
Oncocytoma • Benign oncocytic renal epithelial tumor typically identified incidentally in adults. • The majority of instances are sporadic; nevertheless, certain occurrences are linked to hereditary abnormalities (e.g., Birt–Hogg–Dubé syndrome). Macroscopically, they are well-defined tumors exhibiting a mahogany brown hue, frequently accompanied by core scarring. Histologically, they are distinguished by cells possessing rich granular eosinophilic cytoplasm, proliferating in nests inside an edematous stroma. Oncocytomas are benign tumors that lack the ability for metastatic dissemination. Nonetheless, substantial tumors are frequently resected. • The infiltration of tumor cells into perinephric fat may occur, and this has no detrimental effect.
Angiomyolipoma • A benign mesenchymal tumor of the kidney consisting of varying quantities of adipose tissue, smooth muscle, and robust blood arteries. • Predominantly occurring sporadically in adults, a minor percentage is linked to tuberous sclerosis. These are more likely to be many and bilateral. • While most are discovered inadvertently, they may occasionally manifest with flank pain resulting from hemorrhage into the tumor. Macroscopically, they present as lobulated kidney masses that may exhibit a yellow appearance if their fat content is elevated. Histologically, they consist of a combination of adipose tissue, smooth muscle bundles, and thick-walled blood arteries in varying proportions.
Cystic nephroma • Benign cystic renal tumor with a significant preference for women. • Macroscopically, they are enclosed multicystic lesions devoid of a solid component. The cysts are microscopically bordered by a singular layer of flattened cuboidal epithelial cells. The septa may exhibit cellular regions that resemble ovarian stroma, and notably, the nuclei of the cells within the septa frequently respond to antibodies targeting estrogen and progesterone receptors
Leiomyoma • Benign leiomyomas typically originating from the renal capsule. • The majority manifest in adults as incidental, tiny, well-defined capsular tumors. • Histologically, they exhibit bundles of unremarkable smooth muscle cells.
Renomedullary interstitial cell tumor • Frequently observed benign renal tumors that are sometimes discovered inadvertently during autopsy examinations of the kidneys. Macroscopically, they are little (1–5mm) white nodules located at the center of a medullary pyramid. Histologically, they consist of tiny stellate or polygonal cells embedded in a loose stroma. Entrapped tubules may be located near the periphery of the lesion.
Papillary adenoma • Benign renal epithelial neoplasm exhibiting a papillary or tubulopapillary structure, measuring 5mm or less. • Commonly identified accidentally in nephrectomy specimens or during autopsy. Macroscopically, they are well-defined cortical nodules measuring 5 mm or smaller. Histologically, they consist of non-atypical epithelial cells exhibiting papillary or tubulopapillary arrangements.
Oncocytoma • Benign oncocytic renal epithelial tumor typically identified incidentally in adults. • The majority of instances are sporadic; nevertheless, certain occurrences are linked to hereditary abnormalities (e.g., Birt–Hogg–Dubé syndrome). Macroscopically, they are well-defined tumors exhibiting a mahogany brown hue, frequently accompanied by core scarring. Histologically, they are distinguished by cells possessing rich granular eosinophilic cytoplasm, proliferating in nests inside an edematous stroma. Oncocytomas are benign tumors that lack the ability for metastatic dissemination. Nonetheless, substantial tumors are frequently resected. • The infiltration of tumor cells into perinephric fat may occur, and this has no detrimental effect.
Angiomyolipoma • A benign mesenchymal tumor of the kidney consisting of varying quantities of adipose tissue, smooth muscle, and robust blood arteries. • Predominantly occurring sporadically in adults, a minor percentage is linked to tuberous sclerosis. These are more likely to be many and bilateral. • While most are discovered inadvertently, they may occasionally manifest with flank pain resulting from hemorrhage into the tumor. Macroscopically, they present as lobulated kidney masses that may exhibit a yellow appearance if their fat content is elevated. Histologically, they consist of a combination of adipose tissue, smooth muscle bundles, and thick-walled blood arteries in varying proportions.
Cystic nephroma • Benign cystic renal tumor with a significant preference for women. • Macroscopically, they are enclosed multicystic lesions devoid of a solid component. The cysts are microscopically bordered by a singular layer of flattened cuboidal epithelial cells. The septa may exhibit cellular regions that resemble ovarian stroma, and notably, the nuclei of the cells within the septa frequently respond to antibodies targeting estrogen and progesterone receptors
Leiomyoma • Benign leiomyomas typically originating from the renal capsule. • The majority manifest in adults as incidental, tiny, well-defined capsular tumors. • Histologically, they exhibit bundles of unremarkable smooth muscle cells.
Renomedullary interstitial cell tumor • Frequently observed benign renal tumors that are sometimes discovered inadvertently during autopsy examinations of the kidneys. Macroscopically, they are little (1–5mm) white nodules located at the center of a medullary pyramid. Histologically, they consist of tiny stellate or polygonal cells embedded in a loose stroma. Entrapped tubules may be located near the periphery of the lesion.
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