Sarcomatoid chromophobe renal cell carcinoma: A case report and review of the literature

A Composite Renal Tumor with Dual Differentiation, Chromophobe and Collecting Duct Carcinoma

Chromophobe carcinoma constitutes a small subset of all renal carcinomas. Within this category, rare tumors with divergent differentiation have been recognized. Herein, we report a rare case of composite chromophobe and collecting duct carcinoma and describe its pathologic and clinical features.

Flcn-deficient renal cells are tumorigenic and sensitive to mTOR suppression

Deficiency of tumor suppressor FLCN leads to the activation of the mTOR signaling pathway in human BHD-associated renal cell carcinomas (RCC). We have previously developed a renal distal tubule-collecting duct-Henle's loop-specific Flcn knockout (KO) mouse model (Flcn^flox/flox/Ksp-Cre). This mouse model can only survive for three weeks after birth due to the development of polycystic kidney and uremia. Whether these cystic solid hyperplasia changes seen in those KO mice are tumorigenic or malignant is unknown. In this study, we demonstrated that genetic disruption of Flcn in mouse kidney distal tubule cells could lead to tumorigenic transformation of these cells to develop allograft tumors with an aggressive histologic phenotype. Consistent with previous reports, we showed that the mTOR pathway plays an important role in the growth of these Flcn-deficient allograft and human UOK 257-1 xenograft tumors. We further demonstrated that the mTOR inhibitor, sirolimus, suppresses the tumor's growth, suggesting that mTOR inhibitors might be effective in control of FLCN-deficient RCC, especially in BHD renal tumorigenesis.

Disruption of tubular Flcn expression as a mouse model for renal tumor induction

The study of kidney cancer pathogenesis and its treatment has been limited by the scarcity of genetically defined animal models. The FLCN gene that codes for the protein folliculin, mutated in Birt-Hogg-Dubé syndrome, presents a new target for mouse modeling of kidney cancer. Here we developed a kidney-specific knockout model by disrupting the mouse Flcn in the proximal tubules, thus avoiding homozygous embryonic lethality or neonatal mortality, and eliminating the requirement of loss of heterozygosity for tumorigenesis. This knockout develops renal cysts and early onset (6 months) of multiple histological subtypes of renal neoplasms featuring high tumor penetrance. Although the majority of the tumors were chromophobe renal cell carcinomas in affected mice under 1 year of age, papillary renal cell carcinomas predominated in the kidneys of older knockout mice. This renal neoplasia from cystic hyperplasia at 4 months to high-grade renal tumors by 16 months represented the progression of tumorigenesis. The mTOR and TGF-β signalings were upregulated in Flcn-deficient tumors, and these two activated pathways may synergetically cause renal tumorigenesis. Treatment of knockout mice with the mTOR inhibitor rapamycin for 10 months led to the suppression of tumor growth. Thus, our model recapitulates human Birt-Hogg-Dubé kidney tumorigenesis, provides a valuable tool for further study of Flcn-deficient renal tumorigenesis, and tests new drugs/approaches to their treatment.

Lymphangitic retroperitoneal carcinomatosis occurring from metastatic sarcomatoid chromophobe renal cell carcinoma

A 45-year-old man with left renal mass underwent nephrectomy to reveal a 20-cm tumor diagnosed as sarcomatoid chromophobe renal cell carcinoma. Lymph node metastasis of chromophobe and sarcomatoid components, disseminated tumor in retroperitoneal fat, lymphatic vessels, and perirenal adipose tissue in lymphangitic carcinomatosis pattern were identified. Chromophobe epithelial cells were positive for epithelial membrane antigen, c-Kit, and cytokeratin 7; sarcomatoid cells were positive for CD10 and smooth muscle antigen with high proliferation index. Chromophobe epithelial cells had loss of heterozygosity in chromosomes 1p and 1q, whereas sarcomatoid cells had loss of heterozygosity in 3p, 1p, and 1q. In conclusion, sarcomatoid chromophobe renal cell carcinoma has aggressive biologic behavior and potential to metastasize in unusual patterns.

Chromophobe renal cell carcinoma with concomitant sarcomatoid transformation and osseous metaplasia: a case report

Background

Chromophobe renal cell carcinoma is the third most common form of adult renal epithelial neoplasm. A sarcomatoid component occurs in approximately 8% of all chromophobe renal cell carcinoma cases, while metaplastic bone formation is extremely rare.

Case presentation

An abdominal computed tomography scan revealed a hypovascular tumor with focal calcification, measuring 2.5 × 2.3 cm, in the upper pole of the right kidney. The tumor was clinically diagnosed as a right renal cell carcinoma that showed signs of calcification, and a laparoscopic right radical nephrectomy was performed. The cut surface of the tumor was beige in color and indicated that the tumor was an extensively ossified mass. Histological analysis revealed three distinct morphological components of the tumor. The chromophobe renal cell carcinoma consisted of compact epithelial cells arranged in a nested pattern, and these were mixed with extensive areas of sarcomatoid spindle cells with marked nuclear pleomorphism and brisk mitotic activity. The tumor also contained multiple foci of metaplastic ossification.

Conclusion

Chromophobe renal cell carcinoma with concomitant osseous metaplasia and sarcomatoid transformation is a very rare occurrence.

Sarcomatoid chromophobe renal cell carcinoma: Cytohistopathological correlation of a case

Sarcomatoid renal cell carcinomas of the kidney are rare neoplasms constituting about 1-5% of all renal malignant neoplasms. These are aggressive tumors and are commonly associated with conventional (clear cell) renal cell carcinomas, but cases associated with chromophobe renal cell carcinomas are sparse. Cytological features of such lesions have rarely been reported. Here, we report a unique case of a 48-year-old male patient who presented with right flank lump and pain. A fine needle aspiration was performed from the lesion under ultrasound guidance and a cytological diagnosis of pleomorphic sarcoma was made. A right-sided radical nephrectomy was carried out and subsequent histopathology revealed a sarcomatoid renal cell carcinoma with wide areas of necrosis coexisting with chromophobe renal cell carcinoma with calcification. Differentiation of pleomorphic sarcoma from a sarcomatoid renal cell carcinoma is, thus, challenging from cytopathology smears and the differential diagnoses should always be borne in mind while giving a cytopathological opinion.

Chromosomal gains in the sarcomatoid transformation of chromophobe renal cell carcinoma

The hallmark of chromophobe renal cell carcinoma is multiple chromosomal losses from among chromosomes 1, 2, 6, 10 and 17. Chromophobe renal cell carcinoma with distant metastases or sarcomatoid transformation are uncommon and little is known about their chromosomal abnormalities. We collected six sarcomatoid chromophobe renal cell carcinomas and three primary chromophobe renal cell carcinomas with distant metastases. A cytogenetic analysis by fluorescent in situ hybridization on paraffin-embedded tissue was performed using centromeric probes for chromosomes 1, 2, 6, 10 and 17. We found more than one signal in four of six (66%) sarcomatoid chromophobe renal cell carcinomas, in both sarcomatoid and adjacent epithelial components. Both primary chromophobe renal cell carcinomas and matched metastases showed single signals for all chromosomes studied in two cases and no abnormalities in the remaining case. We concluded that: (1) both epithelial and sarcomatoid components of sarcomatoid chromophobe renal cell carcinoma show different genetic abnormalities from those characteristic of chromophobe renal cell carcinoma; (2) sarcomatoid chromophobe renal cell carcinomas frequently have multiple gains (polysomy) of chromosomes 1, 2, 6, 10 and 17; (3) distant metastases show the same genetic patterns, usually chromosomal losses (monosomy), found in the primary tumors.