A distinct expression pattern and point mutation of c-KIT in papillary renal cell carcinomas

Collecting duct carcinoma of the kidney: an immunohistochemical evaluation of the use of antibodies for differential diagnosis

Collecting duct carcinoma is a highly aggressive renal epithelial malignancy, although it accounts for less than 1% of the incidence of renal epithelial neoplasms. Differential diagnoses between collecting duct carcinoma, pelvic urothelial carcinoma with marked invasion to the renal parenchyma (invasive urothelial carcinoma), and papillary renal cell carcinoma is often challenging. In our current study, we examined the utility of using commercially available antibodies, in conjunction with lectin histochemistry, for such differential diagnoses. We examined 17 cases of collecting duct carcinoma, 10 cases of invasive urothelial carcinoma and 15 cases of papillary renal cell carcinoma (type 1, 6 cases; type 2, 9 cases) in these evaluations. Our results indicated that Ulex europaeus agglutinin 1, E-cadherin, and c-KIT were frequently positive in collecting duct carcinoma and invasive urothelial carcinoma, in comparison with papillary renal cell carcinoma, which had negative results for CD10 and alpha-methylacyl CoA racemase. We found, however, that collecting duct carcinoma showed positivity for high-molecular-weight cytokeratin and low-molecular-weight cytokeratin at a low frequency compared with invasive urothelial carcinoma, and that these distinctions need further careful evaluation. In addition, high-molecular-weight cytokeratin positivity was not a reliable marker for collecting duct carcinoma. We conclude that Ulex europaeus agglutinin 1 reactivity and positivity for E-cadherin and c-KIT are effective in distinguishing collecting duct carcinoma from papillary renal cell carcinoma, and that negative results for alpha-methylacyl CoA racemase and CD10 are potentially useful hallmarks of this distinction also. In contrast, a differential diagnosis for collecting duct carcinoma and invasive urothelial carcinoma will require careful examination of multiple routinely stained specimens, particularly in cases of in situ neoplastic lesions in the pelvic mucosa.

Pathways of Dysregulation in Renal Cell Carcinoma: Rational Approaches to Development of Novel Treatment

Recent developments have involved a series of novel agents that produce clinical benefit in patients with advanced clear-cell renal cell carcinoma (RCC). The molecular characteristics of RCC, pathways involved in growth and progression, and development of targeted therapeutic approaches have become the focus of many investigators in the past decade. A variety of genetic abnormalities, molecular markers and drugs that target these markers or alter the genetic expression of certain regulatory proteins, have been identified and might have clinical significance for prognosis and treatment. However, specific markers associated with RCC and further development of novel single or combination targeted therapies is now required. An understanding of the complicated and unique biologic behavior of RCC and its various histologic subtypes is crucial for the continued development of novel and targeted therapies.

[Gastrointestinal stromal tumors: definition, histological, immunohistochemical, and molecular features, and diagnostic strategy]

Gastrointestinal stromal tumors (GISTs) are the most frequent mesenchymal tumors of the gastrointestinal tract. Major advances in their definition and classification and the understanding of their molecular mechanisms have recently been made. These advances have resulted in the delineation of a treatment that has become a model of targeted therapy in oncology. GISTs are defined as tumors of the gastrointestinal tract, but also of the mesentery and peritoneum, constituted by a proliferation of usually spindle-shaped, rarely epithelioid cells, usually, but not consistently expressing the KIT protein. Most GISTs are associated with molecular abnormalities in two target genes: KIT (which encodes the KIT protein) and PDGFRA (which encodes the A chain of the PDGF receptor). The diagnosis of GIST relies on histological arguments (proliferation of spindle-shaped cells in 70% of cases, of epithelioid cells in 20%; histological variants are rare and sometimes misleading) and on immunohistochemical arguments (expression of KIT in 95%, usually associated with CD34 expression in 60%-70% of cases). The demonstration of mutations in target genes is required only in cases that are histologically suggestive but KIT-negative; beyond this indication, this is only undertaken in research protocols. The differential diagnosis of GIST includes the other mesenchymal tumors of the gastrointestinal tract, such as leiomyomas and leiomyosarcomas, and the digestive locations of some sarcomas; it relies on both histological and immunohistochemical arguments. The evaluation of the prognosis is essential. According to the current concept, every GIST carries a risk of malignancy, which may vary from very low to very high. Prognosis is based on a simple algorithm using two histoprognostic parameters, i.e., tumor size and mitotic index. The treatment of localized GIST is surgical resection, which must be complete; that of advanced or unresectable GIST is based on the use of a targeted therapy, imatinib, which is a pharmacological antagonist of the KIT protein. Proper understanding and utilisation of the diagnostic criteria and classification of GIST by pathologists are essential for good patient management.