Recently Described and Emphasized Entities of Renal Neoplasms

Malignant Mixed Epithelial and Stromal Tumor of the Kidney With 2 Simultaneous Renal Carcinomas in a Male Patient: Case Report and Review of the Literature

The majority of mixed epithelial and stromal tumors (MEST) of the kidney are benign entities found in female patients. Malignant MEST of the kidney is an extremely rare entity that often behaves clinically similar to an undifferentiated sarcoma. We report a case of a malignant MEST with synchronous papillary and clear cell renal cell carcinomas (RCCs) in a 61-year-old Caucasian man who presented with an incidental finding of a left renal mass on workup for back pain. The patient underwent a left radical nephrectomy, with histopathology confirming a malignant MEST, intimately associated papillary RCC, and separate adjacent focus of clear cell RCC.

Extranodal rosai-dorfman disease presenting as a solitary mass with human herpesvirus 6 detection in a pediatric patient

In Rosai-Dorfman disease (RDD), exclusive extranodal involvement with lesions limited to the kidneys is very uncommon and has been described only in adult patients. Occasionally, human herpesvirus 6 (HHV-6) has also been detected in RDD tissue samples. We present the case of a 7-year-old boy referred to our center presenting a single solid mass in the right kidney measuring 3.4 cm, detected both on contrast computed tomography and magnetic resonance imaging. Surgical excision was successfully completed, and the pathology report informed characteristic histopathology and immmunohistochemistry features of RDD. Human herpesvirus 6 was detected and amplified by polymerase chain reaction, as well as by immunohistochemistry. We discuss imaging and histology-based differential diagnoses in the pediatric age group. Although RDD is a rare histiocytic disorder of unknown etiology and pathogenesis, the presence of HHV-6 observed in this case supports the possibility of an abnormal immunologic response linked to viral presence.

Unclassified renal cell carcinoma: a report of 56 cases

What's known on the subject? and What does the study add? Unclassified RCC represents 0.7-5.7% of renal tumours. Limited reported data from two series suggests that unclassified RCC is an aggressive form of RCC, mainly because most cases are at an advanced stage at presentation, but overall and cancer-specific survival were not significantly different between unclassified and clear-cell RCC in an additional series of 38 patients. Our study of 56 cases of unclassified RCC describes the pathological features that can be applied to predict prognosis on a daily basis. In particular nuclear grade, TNM classification, tumour coagulative necrosis, tumour size, microvascular invasion and 2004 WHO histotype are independent predictors of disease-free and cancer-specific survival.

OBJECTIVE

To evaluate the clinicopathological features and outcomes of 56 patients with unclassified renal cell carcinoma (RCC) meeting 2004 World Health Organization diagnostic criteria.

PATIENTS AND METHODS

Urological pathology files of the participating institutions were reviewed and cases of unclassified RCC that met the inclusion criteria were retrieved. Nuclear grade, pT status, tumour size, regional lymph node involvement, distant metastases, coagulative tumour necrosis, mucin and sarcomatoid differentiation were evaluated in radical nephrectomy or nephron-sparing specimens. Significant factors in univariate analysis were then assessed by a multivariate analysis of independent prognostic factors using Cox proportional hazard regression analysis.

RESULTS

Fifty-six cases met the histological criteria for unclassified RCC. Thirty-four (61%) cases were categorized as unrecognizable cell type (mean overall survival 47 months; median 36 months), 20 (36%) as composites of recognized types (mean overall survival 36 months; median 26 months), and two (4%) (mean survival 16 months; median 16 months) as pure sarcomatoid morphology without recognizable epithelial elements. Cox multivariate analysis showed nuclear grade (P = 0.020), stage (P < 0.001), tumour coagulative necrosis (P = 0.018), tumour size (P < 0.001), microvascular invasion (P < 0.001) and tumour histotype (P = 0.028) to be independent predictors of disease-free survival, with tumour size being the most significant (hazard ratio [HR] 9.068, 95% confidence interval [CI] 3.231-25.453). Nuclear grade (P = 0.026), stage (P < 0.001), tumour coagulative necrosis (P < 0.001), tumour size (P = 0.044), microvascular invasion (P < 0.001), tumour recurrence after surgery (P < 0.001) and tumour histotype (P = 0.056) were independent predictors of cancer-specific survival, with tumour recurrence after surgery being the most significant (HR 14.713, 95% CI 5.329-40.622).

CONCLUSION

The prognosis of patients with unclassified RCC seems to be related to clinicopathological features known to be relevant in common forms of RCC.

Molecular Pathology of the Genitourinary Tract: Molecular Pathology of Kidney and Testes

With the advent of newer molecular technologies, our knowledge of cellular mechanisms with tumors of the kidney and testis has grown exponentially. Molecular technologies have led to better understanding of interplay between the von Hippel-Lindau gene and angiogenic cytokines in renal cancer and isochromosome 12p in testicular neoplasms. The result has been development of antiangiogenic-targeted therapy within recent years that has become the mainstay treatment for metastatic renal cell cancer. In the near future, classification and diagnosis of renal and testicular tumors through morphologic analysis will be supplemented by molecular information correlating to prognosis and targeted therapy. This article outlines tumor molecular pathology of the kidney and testis encompassing current genomic, epigenomic, and proteonomic findings.

Cystic nephroma and mixed epithelial and stromal tumour of the kidney: opposite ends of the spectrum of the same entity?

OBJECTIVES

The term "renal epithelial and stromal tumour" (REST) was proposed recently to encompass the spectrum of findings observed in cystic nephroma (CN) and mixed epithelial and stromal tumour (MEST) of the kidney. Our aim was to review the broad spectrum of usual and unusual clinical and morphologic findings observed in CN and MEST.

METHODS

Based on Medline database searches, all aspects of CN and MEST were assessed.

RESULTS

CN and MEST have a remarkable similarity in sex predilection, age distribution, and morphologic attributes of both the epithelial and stromal components and immunohistochemical profile, albeit with variation in individual categories, with higher prevalence of stromal-to-epithelial ratio, prominent ovarian-like stroma, smaller cysts, and stromal luteinisation in MEST, and large cysts, thin septa, and low stromal-to-epithelial ratio in CN. The stromal component in both lesions expresses estrogen and progesterone receptors. Rare and unusual morphologic features, such as endometrioid, cervical, and intestinal differentiation, and luteinised ovarian-like stroma, have been described in MEST. The epithelial element occasionally shows estrogen and progesterone receptors. Rare aggressive behaviour has been reported for both neoplasms.

CONCLUSIONS

Considerable overlap is apparent between the two lesions, which suggests that they may represent opposite ends of the spectrum of the same process. Even though an aggressive behaviour has been reported in very few cases, in general both neoplasms are considered benign and surgical excision is curative.