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  Anatomic Abstracts





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March 2001

Interpreting Crohn’s colitis-like changes in sigmoid diverticulitis specimens
The clinical outcome and optimum classification of patients who have sigmoid resection specimens that show the histologic features of Crohn's disease and diverticulitis is not well defined. In the United States, individuals older than 60 years frequently have sigmoid diverticular disease. CD also has a second incidence peak in this age group and is the most common site of active colonic disease. Historically, these patients were considered to have coexistent diseases, but recent studies have suggested that the CD-like changes are part of the inflammatory reaction of the diverticulitis. The authors conducted a study of 29 such patients. Twenty-five of them had no prior or concurrent CD at the time of surgery; 23 remained free of CD during the followup period (median, six years); and two developed CD in other regions of the bowel. All four patients with CD prior to sigmoid resection continued to have active CD postoperatively. No histologic features of the sigmoid resection specimens could be associated with patient outcome. The authors suggest that CD-like changes within the sigmoid resection specimen are an idiosyncratic inflammatory response to the diverticulosis rather than coexistent CD in the majority of patients who do not have prior or concurrent CD at the time of sigmoid resection. They also caution that pathologists should be wary of making the diagnosis of sigmoid CD in the context of diverticulitis unless CD is found in other parts of the bowel.

Goldstein NS, Leon-Armin C, Mani A. Crohn's colitis-like changes in sigmoid diverticulitis specimens is usually an idiosyncratic inflammatory response to the diverticulosis rather than Crohn's colitis. Am J Surg Pathol. 2000;24(5):668-675.

Reprints: Dr. Neal S. Goldstein, Dept. of Anatomic Pathology, William Beaumont Hospital, 3601 W. Thirteen Mile Rd., Royal Oak, MI 48073

Cytokeratin 7 and cytokeratin 20 expression in epithelial neoplasms from various organ systems: a survey of 435 cases
Cytokeratin 7 and cytokeratin 20 expression recently have been shown to differentiate between various epithelial neoplasms. The authors surveyed 435 epithelial neoplasms from various organ systems by immunohistochemistry using CK 7 and CK 20 monoclonal antibodies. Expression of CK 7 was absent in carcinomas arising from the colon, prostate, kidney, and thymus; carcinoid tumors of the lung and gastrointestinal tract; and Merkel cell tumor of the skin. Most squamous cell carcinomas of various origins were negative for CK 7, except cervical squamous cell carcinoma, in which 87 percent of cases were positive. Approximately two-thirds of cases of malignant mesothelioma were CK 7-positive. CK 20 positivity was seen in a variety of carcinomas, including colorectal carcinoma (100 percent), Merkel cell tumors (80 percent), pancreatic carcinoma (62 percent), gastric carcinoma (50 percent), cholangio-carcinoma (43 percent), and transitional cell carcinoma (29 percent). The expression of CK 20 was virtually absent in carcinomas from other organ systems and malignant mesothelioma. CK 7- and CK 20-negative epithelial neoplasms included adrenal cortical carcinoma, germ cell tumor, prostate carcinoma, renal cell carcinoma, and hepatocellular carcinoma.

Chu P, Wu E, Weiss LM. Cytokeratin 7 and cytokeratin 20 expression in epithelial neoplasms: a survey of 435 cases. Mod Pathol. 2000;13(9):962-972.

Reprints: Dr. Lawrence M. Weiss, Div. of Pathology, City of Hope National Medical Center, 1500 E. Duarte Rd., Duarte, CA 91010

Effect of formalin tissue fixation and processing on immunohistochemistry
Immunohistochemistry is now accepted as the most useful ancillary method in diagnostic histopathology, apart from histochemical stains. It is primarily used to detect differentiation antigens for classifying undifferentiated tumors, lymphomas, and neuroendocrine and soft tissue tumors. Immunohistochemistry is routinely performed by many pathology laboratories, but it still lacks standardization. A major cause of variation in the reproducibility of immunohistochemical staining is induced by tissue fixation and, to a lesser degree, tissue processing. A report, stemming from the first meeting of the International Consensus Group on Standardization and Quality Control, in Nice, France, summarizes the problem and suggests ways to standardize fixation and processing. Most laboratories use neutral-buffered formalin (10 percent) for tissue fixation, which introduces cross-links; coagulative fixatives are less popular. Problems with formalin fixation primarily involve delay of fixation and variations in the duration of the fixation. Solving these problems could entail starting fixation soon (less than 30 minutes) after surgically removing the tissue and avoiding overfixation (longer than 24 to 48 hours). The most significant problem in tissue processing is inadequate tissue dehydration prior to paraffin embedding. This can be prevented by preparing fresh solutions every week depending on the volume of tissue processed. Consistently applying these procedures could eliminate some of the sources of variation in immunohistochemical stains.

Werner M, Chott A, Fabiano A, et al. Effect of formalin tissue fixation and processing on immunohistochemistry. Am J Surg Pathol. 2000;24(7):1016-1019.

Reprints: Dr. Martin Werner, Institut für Allgemeine Pathologie und Pathologische Anatomie, Klinikum rechts der Isar, Technische Universität München, Ismaniger Str. 22, 81675 München, Germany;