Clear cell tubulopapillary renal cell carcinoma

Definition

This is a proposed category of low-grade renal cell tumour not recognised in the WHO 2004 classification.

Synonyms

Renal angiomyoadenomatous tumour
Clear cell papillary renal cell carcinoma of end-stage kidney

Epidemiology

This tumour accounts for about 1% of all adult renal tumours. It occurs across a wide adult age range with a mean of 60 years. Male and female frequency are equal. 10% of cases are bilateral.

Macroscopic appearances

Most tumours are cystic and small (mean 2.4 cm). A minority are multifocal.

Histopathology

The majority of tumours are multicystic. There is a capsule, usually thick and circumferential. The majority of cases have a fibrotic stroma with embedded tumour cells and most include smooth muscle fibres. The cysts contain serosanguinous fluid for colloid-like material. The cysts are lined by a single layer of cuboidal cells with eosinophilic or clear cytoplasm. Almost all cases include tubules and acini with a similar lining. The nuclei of the cuboidal cells tend to be located towards the apical aspect of the cells. Most cases include papillae, which rarely may dominate, again lined by similar cells.

Perirenal invasion, renal sinus invasion, vascular invasion, necrosis and sarcomatoid dedifferentiation are not seen.

Some patients have a concomitant clear cell renal cell carcinoma.

Immunohistochemistry

	CK7	36/361
	Carbonic anhydrase 9	34/361
	CD10	6/361
	AMACR	0/361
	TFE3	0/361

Cytogenetics

There is an absence of 3p deletion and VHL gene mutation or methylation of the gene promotor region.

Differential diagnosis

Clear cell renal cell carcinoma: positive for Carbonic anhydrase 9, CD10 and TFE3 but negative for CK7 and AMACR. Some cases show a papillary architecture but have high grade nuclear appearances, necrosis, sarcomatoid differentiation and invasiveness or metastases.
Clear cell renal cell carcinoma with leiomyomatous stroma: positive for CD10 and CK7.
Multilocular cystic renal cell carcinoma is a variant of clear cell renal cell carcinoma: lacks nests of tubules, acini and papillae
Papillary renal cell carcinoma: positive for CD10, CK7 and AMACR but usually negative for Carbonic anhydrase 9.
Mixed epithelial and stroma tumour: commonly found in young females; there is ovarian-type stroma.

Prognosis

Almost all patients are tumour-free two years after nephrectomy.

References

1 Aydin H, Chen L, Cheng L, Vaziri S, He H, Ganapathi R, et al. Clear cell tubulopapillary renal cell carcinoma: a study of 36 distinctive low-grade epithelial tumors of the kidney. Am J Surg Pathol. 2010 Nov;34(11):1608-21.