Faculty Bibliography

This is a review of several new approaches developed at or adopted by the Cooperative Prostate Cancer Tissue Resource (CPCTR) to resolve issues involved in tissue microarray (TMA) construction and use. CPCTR developed the first needle biopsy TMA, allowing researchers to obtain 200 or more consecutive cancer sections from a single biopsy core. Using radiographs of original paraffin blocks to measure tissue thickness we developed a method to produce TMAs with a larger number of usable sections. The modular approach to plan TMA construction is also a novel concept wherein TMAs of different types, such as tumor grade TMAs, metastasis TMA and hormone refractory tumors TMA can be combined to form an ensemble of TMAs with expanded research utility, such as support for tumor progression studies. We also implemented an open access TMA Data Exchange Specification that allows TMA data to be organized in a self-describing XML document annotated with well-defined common data elements. It ensures inter-laboratory reproducibility because it offers information describing the preparation of TMA blocks and slides. There are many important aspects that may be missed by both beginners and experienced investigators in areas of TMA experimental design, human subjects protection, population sample size, selection of tumor areas to sample, strategies for saving tissues, choice of antibodies for immunohistochemistry, and TMA data management.

We evaluated 35 cases of malignant melanomas with substantial necrosis immunostained with S-100, HMB-45, Melan-A, tyrosinase, PNL2, and microphthalmia transcription factor (MITF). Staining patterns were evaluated in viable and necrotic areas of the tumors. S-100 was the most sensitive marker (97%) in the viable tumors, but necrotic areas demonstrated nonspecific staining. Viable tumors stained variably for HMB-45 (25 [71%]), Melan-A (28 [80%]), tyrosinase (30 [86%]), and PNL2 (23 [66%]). Necrotic areas focally reacted to the same antibodies. The necrotic areas that retained immunoreactivity for these markers corresponded to areas where the outline of the tumor cells could still be recognized as ghost cells on the H&E-stained section. Areas that showed complete coagulative necrosis were negative for melanoma markers. MITF variably stained in the viable tumors but was completely negative in necrotic areas. Our study demonstrated that a combination of antibodies to HMB-45, tyrosinase, and PNL2 detected melanocytic differentiation in necrotic areas in 80% of cases

The determination of tissue thickness in paraffin blocks in the histology laboratory has been largely based on visual estimates. More accurate methods are required for the construction of tissue microarrays (TMAs) to assure a greater yield of cores in sections through the TMA block. We describe an accurate radiographic method to determine tissue thickness in donor paraffin blocks and have validated its application to TMA construction. Individual radiographic analysis was performed on paraffin donor blocks used for the construction of TMAs for determination of donor block tissue thickness. Consecutive numbered slide sections through the TMA block were then examined for the presence or loss of cores in the 150th TMA slide (from the final third of the TMA block) and correlated with the thickness of the individual donor blocks determined radiographically. At the 150th TMA slide, 202 of 1340 cores (15.1%) were depleted. Radiographic measurement showed a greater thickness of the donor paraffin block tissue (2.02 mm) corresponding to the retained cores as compared with the donor tissue (1.54 mm) of the depleted cores (P < 0.001). With progressive slide sections through a TMA block, the retention of tissue cores shows a significant correlation with donor block tissue thickness. Radiographic determination of tissue thickness in donor paraffin blocks can be used in TMA construction. Prior knowledge of tissue thickness in TMA construction can prompt compensatory steps that can enhance the yield of valuable samples and assure sufficient numbers of adequate cores for statistical analysis in biomarker evaluations

We report a case of a 27-year-old woman with a nonpigmented lesion on the right scalp. Histological examination showed a malignant nodular neoplasm with 2 distinct but intimately admixed components: a malignant melanoma with a spindle component and an unusual glandular component. Immunohistochemical studies demonstrated epithelial differentiation on the basis of cytokeratin (CAM5.2 and AE1/AE3) expression in the glandular component and melanocytic differentiation (HMB-45, PNL2, MITF, and S-100) of the spindle cell component. A single melanocytic marker (MITF) was expressed in both components, raising the possibility of dual differentiation in a single tumor, rather than the alternative considerations of a collision tumor or a reactive pseudoepitheliomatous hyperplasia with eccrine duct lumen formation within a melanoma. This unusual tumor with both melanocytic and epithelial components may represent a true melanocarcinoma, which becomes a plausible consideration, in view of melanoma plasticity and recent experimental evidence and speculation about the role of stem cells in melanoma

IL-17RC (interleukin-17 receptor-like) gene codes for a transmembrane protein, the full length of which inhibits apoptosis in prostate cancer cells. IL-17RC gene transcribes over a dozen different splice variants of mRNA. However, it is not known whether there are relevant protein isoforms. Here we report that different IL-17RC protein isoforms were detected by two different antibodies. The isoform as detected byanti-IL-17RC intracellular domain antibodies (anti-ICD) was expressed at higher levels in androgen-independent prostate cancer cell lines (PC3 and DU145) than in androgen-dependent prostatic cell lines (RWPE-1, pRNS-1-1, MLC-SV40, and LNCaP). In contrast, several isoforms as detected by anti-IL-17RC extracellular domain antibodies (anti-ECD) were expressed at significantly higher levels in androgen-dependent prostatic cell lines than in androgen-independent ones. Furthermore, immunohistochemical staining of prostate tissue microarrays showed that IL-17RC protein expression was significantly higher in androgen-independent prostate cancers than in androgen-dependent ones when anti-ICD was used, whereas the trend was reversed using anti-ECD. These observations provide evidence that IL-17RC protein isoforms are differentially expressed in prostatic cells and cancer tissues and may play a negative or positive role in the initiation and progression of prostate cancer

Tissue microarrays (TMAs) are a valuable resource that have been used for molecular profiling and biomarker development. The high throughput and cost savings make TMAs well suited for the rapid screening of large patient populations and for use in multitissue studies. Construction and casting is time consuming and the most important step in the use of a TMA. Occasionally, improper casting of a TMA leads to failure of the block. Similarly, repeated sectioning can cause the block to become too thin to collect additional sections. Considering the increased use of TMA and their occasional failure, we developed a method to repair fractured blocks or blocks worn thin from repeated sectioning

Nephrogenic adenoma is a rare lesion of the urinary tract. The diagnosis usually is straightforward when characteristic microscopic and clinical findings are present, and the entity is familiar. However, misdiagnosis, in particular of adenocarcinoma of the prostate gland, may occur. Immunohistochemical stains often are needed to make such a distinction, but currently available markers offered only partial help. It recently was demonstrated that nephrogenic adenoma in renal transplant patients originated from the renal tubular epithelium. This newly proved, but long sought information may be helpful in the differential diagnosis of neophrogenic adenoma. In this study, we investigated the expression of a renal transcription factor, PAX2, in 39 nonrenal transplant-related nephrogenic adenomas, 100 adenocarcinomas of the prostate gland, and 47 urothelial carcinomas of the urinary tract. A strong and distinct nuclear staining of PAX2 was found in all 39 cases of nephrogenic adenoma (100%), but not in normal prostate tissue, normal urothelium, adenocarcinomas of the prostate gland, and invasive urothelial carcinomas. Focal CD10 was detected in six of 13 nephrogenic adenomas in the superficial papillary component and in normal prostate epithelium, normal urothelium, lymphocytes, adenocarcinoma of the prostate gland, and urothelial carcinoma. There was no uroplakins detected in nephrogenic adenoma. Therefore, these findings are suggesting that nephrogenic adenoma in nonrenal transplant patients may also arise from the renal epithelium, as did the comparable lesions after transplantation. PAX2 is a specific and sensitive immunohistochemical marker in identification and differential diagnosis of nephrogenic adenoma.Modern Pathology advance online publication, 6 January 2006; doi:10.1038/modpathol.3800535