Alan D. Ramsay

Five cases of B-cell lymphoma are described in which the morphology and initial immunohistochemistry suggested a diagnosis of T-cell neoplasia. In four cases, the histological picture was that of an adult pleomorphic T-cell lymphoma; the fifth case was a lymphocytic lymphoma (CLL) with an accompanying T-cell lymphocytosis in the peripheral blood. Immunohistochemistry on both frozen and paraffin-embedded material showed that the cellular population in all five cases consisted mainly of T-cells; less than 10% of the cells stained as B-cells. However, immunoglobulin immunostaining combined with use of the new lineage-related monoclonal antibodies reactive in paraffin section revealed that the B-cells constituted the neoplastic population. Genetic analysis showed no evidence of clonality in the T-cells, nor was it able to detect rearrangement in the small number of clonal B-cells present. These cases represent a variety of B-cell neoplasia that mimicks T-cell lymphoma morphologically and immunologically. The vigorous T-cell reaction seen in such lymphomas means that the malignant population can be correctly identified only by careful examination of the immunohistochemical findings.

UCHL1 is a murine monoclonal antibody that recognises a 180-185 kD determinant on CD4 (72%) and CD8 (36%) positive T cells. This antibody is effective in formalin fixed and paraffin embedded tissues, using the immunoperoxidase method. One hundred and forty three cases of malignant lymphoma were examined. Neoplastic cells in 100% of cases of Mycosis fungoides (n = 10), 83% of cases of peripheral T cell lymphoma (n = 25), and 78% of cases of (T-ALL) T acute lymphoblastic lymphoma (n = 9) were stained by this antibody. In addition, staining was seen in 100% of cases of malignant histiocytosis of the intestine (n = 13), a condition now thought to be a T cell lymphoma. Two cases of true histiocytic lymphoma were also positive. This antibody stained neither the neoplastic cells in a wide range of B cell lymphomas (n = 62) nor Reed-Sternberg cells in 16 cases of Hodgkin's disease. UCHL1 also stained neoplastic cells in four cases of granulocytic sarcoma. A panel of normal tissues was similarly studied. Staining was seen in normal T cells and mucosal intraepithelial lymphocytes, macrophages, mature myeloid cells, and endometrial stromal granulocytes. UCHL1 is a monoclonal antibody that identifies T cells in formalin fixed paraffin embedded tissues, and should prove useful for diagnosing T cell lymphomas, especially when only formalin fixed tissue is available for diagnosis.

The histopathological diagnosis is the bedrock of modern oncology, and plays a major role in the treatment of many other types of disease. Errors in these reports can critically affect patient care and may become the subject of media concern. This article considers how audit in histopathology can provide information about errors and inconsistencies in the diagnosis of surgical specimens. The use of audit to generate information about the background level of errors in pathology reports is reviewed, along with findings about the nature of these errors and the types of specimens more commonly affected. Generic audit strategies that can be used to minimize the risk of errors in reports are discussed, together with the use of audit to evaluate diagnostic criteria and pathological scoring or grading systems. The role of audit in determining the informational content of reports is included, and there is consideration of the relationship between sample size and error rates. The limited extent to which audit can be used to assess the performance of individual pathologists is also covered.

In order to assess the performance of a surgical pathology laboratory in a university hospital, we have established a comprehensive system of quality audit based on peer review. Each month, 2% of cases received are selected at random and assessed retrospectively by two senior pathologists. The system, which uses semi-quantitative scoring, examines diagnostic accuracy, identifies delay at any stage in the production of reports, evaluates the overall quality of the slides, the presentation of the final report, and the accuracy of the SNOMED coding. Each of these parameters is graded as "satisfactory," "borderline," or "unsatisfactory." In 20 of 518 cases (3.9%) analyzed in 18 months, the microscopic report was unsatisfactory; in six of these cases, the error could have affected patient management. Remediable faults were detected in the macroscopic description of specimens and in the speed and accuracy of report typing by the secretarial staff. In 13 of 18 months, greater than 10% of reports were delayed because of the time taken in microscopic reporting by pathologists. Some (but not all) of this delay was attributable to the "checking out" of pathologists in training. We conclude that this audit system has uncovered substantial deficiencies in our departmental performance, some of which could affect the clinical course of patients. These surprising results suggest that a system of peer review should be adopted more widely.