Phyllodes tumors (PTs) of the breast are biphasic lesions, comprising an epithelial component set within a neoplastic spindle-celled stroma. These tumors have been classified as benign, borderline, and malignant based on a combination of histological criteria, including stromal cellularity, nuclear pleomorphism, mitotic rate, stromal overgrowth, and margin appearance. The aim of this study was to evaluate the expression of CD34, CD117 (c-kit), and Ki-67 in PT of the breast and attempt to correlate the staining pattern with tumor grade by morphology. Immunohistochemical expression of CD117, CD34, and Ki-67 was studied on formalin-fixed, paraffin-embedded archival tissue material from 33 cases of PT. Histologically, there were 21 benign, 6 borderline, and 6 malignant (high-grade) tumors. All 6 histologically malignant PTs were positive for CD117 (100%), but only 1 marked with CD34 (16.7%). Borderline PTs frequently coexpressed CD34 and CD117 (66.7%). The benign PTs, on the other hand, most commonly (52.4%) showed a CD34(+)/CD117(-) immunoprofile with 33.3% cases coexpressing the markers: that is, CD34(+)/CD117(+). Although most benign PTs (80.6%) showed a Ki-67 of <2%, a few cases showed slightly higher proliferation indices. This study indicates that CD34 and CD117 are differentially expressed in benign and malignant PTs. These markers, therefore, in combination, may be used as an adjunct to morphology in the subclassification of PTs.

Primary, well-differentiated neuroendocrine (carcinoid) tumors of the extrahepatic biliary ducts are an uncommon cause of biliary obstruction. As compared to cholangiocarcinomas, which are more commonly seen at this location, these tumors tend to behave less aggressively, and only one-third metastasize. Tumor size (&gt;2 cm) appears to be the best predictor of aggressive behavior. Surgery is the mainstay of treatment and complete resection offers prolonged disease-free survival. Accurate preoperative diagnosis is therefore important and can be made by examining brush cytology specimens obtained during endoscopic retrograde cholangiopancreatography and/or endoscopic ultrasound-guided fine-needle aspiration. It is important to keep this entity in mind, especially when examining cytologic or small biopsy specimens, so that appropriate immunohistochemical stains can be used to arrive at the correct diagnosis.