Kim L. Wang

A Molecular Classification of Papillary Renal Cell Carcinoma

Despite the moderate incidence of papillary renal cell carcinoma (PRCC), there is a disproportionately limited understanding of its underlying genetic programs. There is no effective therapy for metastatic PRCC, and patients are often excluded from kidney cancer trials. A morphologic classification of PRCC into type 1 and 2 tumors has been recently proposed, but its biological relevance remains uncertain. We studied the gene expression profiles of 34 cases of PRCC using Affymetrix HGU133 Plus 2.0 arrays (54,675 probe sets) using both unsupervised and supervised analyses. Comparative genomic microarray analysis was used to infer cytogenetic aberrations, and pathways were ranked with a curated database. Expression of selected genes was validated by immunohistochemistry in 34 samples with 15 independent tumors. We identified two highly distinct molecular PRCC subclasses with morphologic correlation. The first class, with excellent survival, corresponded to three histologic subtypes: type 1, low-grade type 2, and mixed type 1/low-grade type 2 tumors. The second class, with poor survival, corresponded to high-grade type 2 tumors (n = 11). Dysregulation of G1-S and G2-M checkpoint genes were found in class 1 and 2 tumors, respectively, alongside characteristic chromosomal aberrations. We identified a seven-transcript predictor that classified samples on cross-validation with 97% accuracy. Immunohistochemistry confirmed high expression of cytokeratin 7 in class 1 tumors and of topoisomerase IIalpha in class 2 tumors. We report two molecular subclasses of PRCC, which are biologically and clinically distinct and may be readily distinguished in a clinical setting.

Overexpression of glutathione s-transferase alpha in clear cell renal cell carcinoma.

To determine its diagnostic value, we evaluated glutathione S-transferase alpha (GST-alpha) expression in a large number of renal cell carcinomas (RCCs). GST-alpha messenger RNA (mRNA) levels from 70 renal neoplasms were analyzed with complementary DNA (cDNA) microarray chips containing 21,632 cDNA clones. Furthermore, 348 primary renal tumors and 24 metastatic RCCs were subjected to immunohistochemical analysis with a GST-alpha-specific antibody. GST-alpha mRNA was elevated significantly (11.4-fold) in a majority of clear cell RCCs (28/43 [65.1%]; 28/39 [71.8%] with adjustments for informative spots) compared with other kidney tumors (1/27 [3.7%]). Strong and diffuse GST-alpha immunoreactivity was demonstrated in a majority of clear cell (166/202 [82.2%]; mean intensity, 2.41) and metastatic clear cell RCCs (17/24 [70.8%]; mean intensity, 2.62). Other renal tumor types did not exhibit significant GST-alpha immunoreactivity, confirming mRNA results. Through cDNA microarrays and immunohistochemical analysis, we demonstrated GST-alpha as a biomarker for clear cell RCCs.

Signet-Ring Cell Change Versus Signet-Ring Cell Carcinoma: A Comparative Analysis

Signet-ring cell change (SCC) is a nonneoplastic condition that morphologically simulates signet-ring cell carcinoma (SRCA). The few case reports on SCC have focused on morphologic characteristics in distinguishing benign from malignant. In biopsy specimens, however, SCC can be easily confused with SRCA, which often demonstrates innocuous cytologic features. The object of this study is twofold: 1) to report 14 additional cases of SCC, comparing their morphologic and phenotypic features with that of SRCA; and 2) to evaluate the incidence of SCC in pseudomembranous colitis. Paraffin sections of biopsy or resection specimens containing focal or extensive SCC and 5 cases of colonic SRCA were stained with hematoxylin and eosin, periodic-acid Schiff stain with and without diastase digestion, and by standard ABC immunoperoxidase procedure using antibodies to E-cadherin, p53, and Ki-67. Both cells in SCC and SRCA were strongly positive for neutral mucins. Cells in SCC were strongly positive for E-cadherin and negative for p53 and Ki-67. In contrast, cells in SRCA were strongly positive for p53, exhibited high proliferation, and demonstrated absent or weak positivity for E-cadherin. Although SCC is not well recognized in pseudomembranous colitis, the incidence is fairly high: 14 of 50 (28%) cases showed variable numbers of signet-ring cells. Extensive SCC, although rare, can occur in different clinical conditions and can be easily mistaken for SRCA. When in doubt, routine immunohistochemical stains such as p53, Ki-67, and E-cadherin can help to differentiate SCC from SRCA.

Overexpression of Glutathione S-Transferase α in Clear Cell Renal Cell Carcinoma

To determine its diagnostic value, we evaluated glutathione S-transferase α (GST-α) expression in a large number of renal cell carcinomas (RCCs). GST-α messenger RNA (mRNA) levels from 70 renal neoplasms were analyzed with complementary DNA (cDNA) microarray chips containing 21,632 cDNA clones. Furthermore, 348 primary renal tumors and 24 metastatic RCCs were subjected to immunohisto-chemical analysis with a GST-α–specific antibody. GST-α mRNA was elevated significantly (11.4-fold) in a majority of clear cell RCCs (28/43 [65.1%]; 28/39 [71.8%] with adjustments for informative spots) compared with other kidney tumors (1/27 [3.7%]). Strong and diffuse GST-α immunoreactivity was demonstrated in a majority of clear cell (166/202 [82.2%]; mean intensity, 2.41) and metastatic clear cell RCCs (17/24 [70.8%]; mean intensity, 2.62). Other renal tumor types did not exhibit significant GST-α immunoreactivity, confirming mRNA results. Through cDNA microarrays and immunohistochemical analysis, we demonstrated GST-α as a biomarker for clear cell RCCs.

Immunohistochemical Expression of Matrix Metalloproteinases 1, 2, 9, and 14 in Dermatofibrosarcoma Protuberans and Common Fibrous Histiocytoma (Dermatofibroma)

CONTEXT Common fibrous histiocytoma (cFH) or dermatofibroma and dermatofibrosarcoma protuberans (DFSP) are 2 spindle cell mesenchymal tumors that are distinguished in part by their microscopic growth patterns and clinically by the greater propensity for DFSP to recur. Matrix metalloproteinases (MMPs) potentially play a role in modulating the growth patterns of cFH and DFSP by remodeling the extracellular matrix. OBJECTIVE To evaluate the immunohistochemical (IHC) expression of MMP-1, MMP-2, MMP-9, and MMP-14 in DFSP and cFH, because (1) MMP-1, MMP-2, MMP-9, and MMP-14 are synthesized by dermal fibroblasts, the major constituent of DFSP and cFH; and (2) platelet-derived growth factor B, which is overexpressed in most examples of DFSP because of t(17;22), activates ets-1, a transcription factor that regulates molecules associated with tumor invasion and metastasis, including MMP-1, MMP-3, and MMP-9. DESIGN Immunohistochemical studies were performed on archived, formalin-fixed, paraffin-embedded tissue of DFSP (n = 48) and cFH (n = 47).Results.-Significant IHC expression (>10% of tumor cells) in cFH included MMP-14 (27 [59%] of 46 tumors positive), MMP-2 (21 [47%] of 45 tumors positive), MMP-9 (9 [20%] of 45 tumors positive), and MMP-1 (6 [13%] of 46 tumors positive). No DFSPs showed significant IHC expression of any of the MMPs evaluated. However, anti- MMP-2 highlighted a rich microvascular element within deep tumor tissue present in 81% of DFSPs with a prominent subcutaneous component. CONCLUSION Our IHC results indicate that MMP-1 and MMP-9 are not up-regulated in DFSP. Convincing expression of MMP-14 in cFH suggests that this MMP may affect the growth pattern of the lesion, perhaps by activating MMP-2 expression in tumor cells. In DFSP, MMP-2 may play a role in tumor angiogenesis.

Ferruginous Bodies on Frozen Section

63-year-old man with a history of extensive asbestos exposure and cigarette smoking presented with shortness of breath. The asbestos exposure occurred while the patient was employed as a pipe insulator during the years 1959 to 1973. A computed tomographic scan of the lungs demonstrated bilateral pleural effusions, bilateral pleural plaques, and a 1.3-cm mass in the left lower lung lobe. A left lower lobectomy was performed, and sectioning of the lung demonstrated a 1.3-cm firm, tan-pink mass which was representatively frozen. Microscopically, the frozen section showed adenocarcinoma (Figure 1) associated with ferruginous bodies (Figure 1, arrow). Higher magnification of the ferruginous bodies demonstrated