CAP TODAY Pathology/Laboratory Medicine/Laboratory Management
Molecular investigation of lymph nodes in colon cancer patients using OSNA
A new diagnostic system, called one-step nucleic acid amplification, detects cytokeratin 19 mRNA as a surrogate for lymph node metastases. The authors conducted a prospective investigation to compare the performance of one-step nucleic acid amplification (OSNA) with standard hematoxylin-and-eosin (H&E) analysis and intensive histopathology for detecting colon cancer lymph node metastases. In total, 313 lymph nodes from 22 consecutive patients with stages one, two, and three colon cancer were assessed. Half of each lymph node was analyzed initially by H&E followed by an intensive histologic workup (five levels of H&E and immunohistochemistry analyses, the gold standard for assessing the sensitivity and specificity of OSNA), and the other half was analyzed using OSNA. The authors found that OSNA was more sensitive for detecting small lymph node tumor infiltrates than H&E (11 results were OSNA positive and H&E negative). Compared with intensive histopathology, OSNA had 94.5 percent sensitivity, 97.6 percent specificity, and a concordance rate of 97.1 percent. OSNA resulted in an upstaging of two of 13 patients (15.3 percent) with lymph node-negative colon cancer after standard H&E examination. The authors concluded that OSNA appears to be a powerful and promising molecular tool for detecting lymph node metastases in patients with colon cancer. It performed similarly to intensive histopathologic investigations for detecting lymph node metastases and appeared to be superior to standard histology with H&E. Furthermore, OSNA may lead to a potential upstaging of more than 15 percent of patients with colon cancer.
Gόller U, Zettl A, Worni M, et al. Molecular investigation of lymph nodes in colon cancer patients using one-step nucleic acid amplification (OSNA): A new road to better staging? Cancer. 2012;118(24):6039–6045.
Correspondence: Dr. Markus Zuber at markus. zuber@spital.so.ch
Thymidylate synthase expression and molecular alterations in adenosquamous carcinoma of the lung
Thymidylate synthase expression is higher in squamous cell carcinoma than in adenocarcinoma of the lung. It is thought that this is the reason for the poor efficacy of pemetrexed in squamous cell carcinoma. However, data are limited with regard to thymidylate synthase expression in adenosquamous carcinoma, a distinct subtype of lung cancer containing squamous and glandular differentiation. Furthermore, molecular alterations, such as epidermal growth factor receptor and Kirsten rat sarcoma 2 viral oncogene homolog mutations, which are seen in adenocarcinomas, are not well understood in mixed histology tumors, including adenosquamous carcinoma. The authors conducted a study to better characterize adenosquamous tumors of the lung. Using immunohistochemistry to evaluate thymidylate synthase protein levels, the authors found that expression of thymidylate synthase in these mixed tumors roughly paralleled that of squamous cell carcinoma, instead of falling in between squamous cell and adenocarcinoma. Of note, the expression of thymidylate synthase in adenosquamous samples was more closely correlated within the two components than would be expected by random chance alone. Furthermore, the authors noted a relatively high rate of epidermal growth factor receptor (11 percent) and Kirsten rat sarcoma 2 viral oncogene homolog (33 percent) mutations in these specimens, with the mutations showing convergence in the glandular and squamous components upon micro-dissection. The authors concluded that these results indicate that adenosquamous carcinomas are not simple mixtures of their two histological components but, rather, behave as distinct entities. This is important in further understanding their behavior. Given the similarity between thymidylate synthase expression in squamous cell and adenosquamous carcinoma, and that thymidylate synthase is the main target of pemetrexed, the authors extrapolated that pemetrexed may also have inferior clinical activity in adenosquamous carcinoma.
Shu C, Cheng H, Wang A, et al. Thymidylate synthase expression and molecular alterations in adenosquamous carcinoma of the lung. Mod Pathol. 2013;26:239–246.
Correspondence: Dr. A. C. Borczuk at ab748@columbia.edu
Microdensitometry of osteopontin as a prognostic biomarker in colorectal carcinoma tissue microarrays
The authors conducted a study to explore the potential and limitations of “biomarker pathology” with quantitative immunohistochemistry on tissue microarrays, using osteopontin and colorectal carcinoma as a model system. Microdensitometry for quantitative evaluation of osteopontin immunohistochemistry (clone OP3N) on digital microphotographs using the public domain software ImageJ was observed to be straightforward and reliable. However, using colorectal carcinoma cell lines (n=11), the correlation between densitometric evaluations of Western blots and microdensitometry of immunocytochemistry of slide cultures was only moderate. A virtual resampling method to simulate tissue microarrays showed that, due to the heterogeneity of immunostaining, tumors were misclassified in nearly 20 percent of the arrays, even if four punches were used. Micro-densitometric evaluation of a tissue microarray made of a clinicopathologically well-characterized series of colorectal carcinomas with long-term followup (222 cases evaluable in the tissue microarray; Union Internationale Contre le Cancer [UICC] stages I–III/R0) showed a moderate survival advantage for patients with high osteopontin expression by microdensitometry. The authors concluded that these results challenge the basic assumption that microdensitometry is a precise technique for quantifying proteins detected by immunohistochemistry and delineate drawbacks when working with tissue microarrays in clinicopathological studies.
Prall F, Maletzki C, Linnebacher M. Microdensitometry of osteopontin as an immunohistochemical prognostic biomarker in colorectal carcinoma tissue microarrays: potential and limitations of the method in ‘biomarker pathology’. Histopathology. 2012;61(5):823–832.
Correspondence: Dr. Friedrich Prall at friedrich.prall@med.unirostock.de
Evaluation of pathological and molecular features in clinically aggressive dermatofibromas
Dermatofibroma, or cutaneous fibrous histiocytoma, represents a common benign mesenchymal tumor, and numerous morphological variants have been described. Some variants of dermatofibroma are characterized by an increased risk of local recurrences, and a few cases of metastasis have been reported. Unfortunately, aggressive behavior cannot be predicted reliably by morphology. The authors evaluated the value of array-comparative genomic hybridization in this setting. Seven cases of clinically aggressive dermatofibromas were identified, and pathological and molecular features were evaluated. The neoplasms occurred in four female and three male patients (mean age, 33 years; range, 2–65 years) and arose on the shoulder, buttock, temple, lateral neck, thigh, ankle, and cheek. The size of the neoplasms ranged from 1 cm to 9 cm (mean, 3 cm). An infiltration of the subcutis was seen in five cases. Two neoplasms were completely excised, and an incomplete or marginal excision was reported in the remaining cases. Local recurrences were seen in six cases (time to the first recurrence, eight months to nine years). Metastases were noted between three months and eight years after diagnosis in six patients. Two patients died of disease, and two patients were alive with disease. Histologically, the primary tumors showed features of cellular dermatofibroma (four cases), cellular/aneurysmal dermatofibroma (one case), atypical/cellular dermatofibroma (one case), and classical dermatofibroma (one case). Mitotic figures ranged from three to 25 per 10 high-power fields, and focal necrosis was present in five cases. Interestingly, malignant transformation from cellular dermatofibroma to an obvious spindle cell/pleomorphic sarcoma was seen in one primary and one recurrent neoplasm. Five neoplasms showed chromosomal aberrations by array-comparative genomic hybridization, suggesting that these changes may represent an additional diagnostic tool for identifying cases of dermatofibroma with metastatic potential.
Mentzel T, Wiesner T, Cerroni L, et al. Malignant dermatofibroma: clinicopathological, immunohistochemical, and molecular analysis of seven cases. Mod Pathol. 2013;26:256–267.
Correspondence: Dr. T. Mentzel at mentzel@dermpath.de
Interobserver agreement in the reporting of colorectal polyp pathology by bowel cancer screening pathologists
The authors conducted a study to assess interobserver agreement in the reporting of colorectal polyps among histopathologists participating in the Welsh Bowel Cancer Screening (BCS) program. Twelve benign polyps representative of BCS cases were identified from pathology files and reported by 28 BCS histopathologists using proforma sheets. The level of agreement between the participants and a gold standard was determined using kappa statistics. A moderate level of agreement was achieved in the reporting of polyp type (›=0.45; 95 percent confidence interval [CI], 0.34–0.59), and adenomatous lesions were distinguished from nonadenomatous lesions in 96 percent of cases. Substantial agreement was obtained in distinguishing low- and high-grade dysplasias (›=0.67; 95 percent CI, 0.50–0.86), but there was only fair agreement in reporting excision margin status (›=0.24; 95 percent CI, 0.07–0.43), with frequent use of the “uncertain” category. Significant issues were noted in categorizing serrated lesions, recognizing focal high-grade dysplasia and epithelial misplacement, and diagnosing villous change in adenomas. The authors concluded that interobserver variability in some aspects of BCS pathologists’ reporting of colorectal polyps is suboptimal, with a potential impact on patient management and efficient operation of the screening service.
Turner JK, Williams GT, Morgan M, et al. Interobserver agreement in the reporting of colorectal polyp pathology among bowel cancer screening pathologists in Wales. Histopathology. 2013;62(6):916–924.
Correspondence: S. Dolwani at sunil.dolwani@wales.nhs.uk