Renal oncocytoma pathophysiology

Renal oncocytoma Microchapters
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Homa Najafi, M.D.[2] Shanshan Cen, M.D. [3]

Overview

The exact pathogenesis of [disease name] is not fully understood.

OR

It is thought that [disease name] is the result of / is mediated by / is produced by / is caused by either [hypothesis 1], [hypothesis 2], or [hypothesis 3].

OR

[Pathogen name] is usually transmitted via the [transmission route] route to the human host.

OR

Following transmission/ingestion, the [pathogen] uses the [entry site] to invade the [cell name] cell.

OR

[Disease or malignancy name] arises from [cell name]s, which are [cell type] cells that are normally involved in [function of cells].

OR

The progression to [disease name] usually involves the [molecular pathway].

OR

The pathophysiology of [disease/malignancy] depends on the histological subtype.

Pathophysiology

Physiology

The normal physiology of [name of process] can be understood as follows:

Pathogenesis

• The exact pathogenesis of [disease name] is not completely understood.

OR

• It is understood that [disease name] is the result of / is mediated by / is produced by / is caused by either [hypothesis 1], [hypothesis 2], or [hypothesis 3].
• [Pathogen name] is usually transmitted via the [transmission route] route to the human host.
• Following transmission/ingestion, the [pathogen] uses the [entry site] to invade the [cell name] cell.
• [Disease or malignancy name] arises from [cell name]s, which are [cell type] cells that are normally involved in [function of cells].
• The progression to [disease name] usually involves the [molecular pathway].
• The pathophysiology of [disease/malignancy] depends on the histological subtype.

Genetics

[Disease name] is transmitted in [mode of genetic transmission] pattern.

OR

Genes involved in the pathogenesis of [disease name] include:

• [Gene1]
• [Gene2]
• [Gene3]

OR

The development of [disease name] is the result of multiple genetic mutations such as:

• [Mutation 1]
• [Mutation 2]
• [Mutation 3]

Associated Conditions

Conditions associated with [disease name] include:

• [Condition 1]
• [Condition 2]
• [Condition 3]

Grossly renal oncocytomas are well-circumscribed, tan-brown or mahogany-colored masses with a central stellate scar.[2] The central scar is characteristic of renal oncocytoma, but it is not specific for this entity and is not always present.[2] Grossly, oncocytoma can occasionally interdigitate with perinephric fat. When it does this, there does not appear to be any stromal reaction or response in the fat. This does not change benign behavior.[2] Similarly,  a small portion of tumors may have vascular invasion.

Microscopically, renal oncocytomas appear well-circumscribed. The mass is composed of nests and tubular structures line by round to polygonal cells with abundant granular eosinophilic cytoplasm. The cells have uniform nuclei with prominent central nucleoli.[1] The background stroma is edematous, myxomatous, or hyalinized.[6] Other possible architectural patterns include compact nesting, solid, focal rare abortive papillary structures, and cystic spaces.[2] One variation is a small cell oncocytoma, which occurs when there are areas with scant cytoplasm.

It is well established that oncocytomas may contain a degree of cytologic atypia, which is thought to be degenerative. This atypia may include increased nuclear size, irregular nuclear contours, and smudged chromatin.[2] Mitosis is extremely rare in oncocytoma, and more than one mitotic figure should not be found.[2]

Clinicians can confirm the diagnosis of oncocytoma with immunohistochemistry. The most common stain used is cytokeratin 7, which is minimally positive and limited to scattered individual cells or small clusters. AMACR may be positive in low intensity. Oncocytoma should have membranous positivity for CD117. Other positive stains include cyclin D1, kidney-specific cadherin, S100A1, and E-cadherin.[7][2] Colloidal iron staining is often described as helpful in diagnosis, but there is wide variation in staining techniques that can make interpretation challenging. If used, colloidal iron staining should be negative.[2] Vimentin may be focally positive at the edge of the central scar but should not be diffusely positive.[2] Oncocytoma will be negative for melanocytic markers.

If evaluated on a cytology specimen, oncocytoma will have large cells with granular cytoplasm, regular nuclei with tiny nucleoli, and minimal atypia.[8]

Gross Pathology

On gross pathology, [feature1], [feature2], and [feature3] are characteristic findings of [disease name].

Microscopic Pathology

On microscopic histopathological analysis, [feature1], [feature2], and [feature3] are characteristic findings of [disease name].

Overview

On gross pathology, tan or mahogany brown, well circumscribed tumor, and central scar are characteristic findings of renal oncocytoma. On microscopic histopathological analysis, oncocytes and large eosinophilic cells are characteristic findings of renal oncocytoma.

Pathogenesis

• Renal oncocytoma is thought to arise from the intercalated cells of collecting ducts of the kidney.

Gross Pathology

• The tumors are tan or mahogany brown, well circumscribed, and contain a central scar. They may achieve a large size (up to 12 cm in diameter).

• 
  Renal oncocytoma

Microscopic Pathology

• An epithelial tumor composed of oncocytes, large eosinophilic cells having small, round, benign-appearing nuclei with large nucleoli and excessive amounts of mitochondria.

• 
  Renal oncocytoma

Genetics

• Genes involved in the pathogenesis of renal concocytoma may include mtDNA MTND6 and FLCN.