Lymphocytic Surface Markers in Lymphoid Leukemoid Reactions

Expression of JL1 is an effective adjunctive marker of leukemia cutis

CONTEXT

Specific differentiation of leukemia cutis (LC) from nonleukemic dermatoses is crucial to ensure proper treatment for the disease. Because of the exceptionally variable histologic features of LC and the frequent nonleukemic dermatoses in leukemia patients, identification of leukemic cells that infiltrate skin lesions is important. Here, we introduce JL1, a novel leukemia-associated surface antigen, which is not expressed in mature human tissue but in cortical thymocytes and small subpopulations of bone marrow hematopoietic precursors.

OBJECTIVES

To assess the expression pattern of JL1 in LC and compare it with other commonly used markers. Also, to evaluate the expression of JL1 in other cutaneous lesions that need differential diagnoses.

DESIGN

Immunohistochemical staining with anti-JL1 and other commonly used markers for LC was performed on paraffin-embedded skin biopsies from 32 cases of LC with acute lymphoblastic leukemia/lymphoma and acute myelogenous leukemia. Immunohistochemical staining score was evaluated in each case according to the proportion of positive tumor cells found. JL1 staining was also done on 96 reactive or neoplastic cutaneous lesions.

RESULTS

JL1 was detected in 7 of 11 acute lymphoblastic leukemia/lymphoma LC (63.6%) and 7 of 21 acute myelogenous leukemia LC (33.3%), with invariably high-staining scores. None of the other cutaneous lesions or normal tissues expressed JL1. The expression pattern of JL1 was not altered in 2 patients with follow-up biopsies.

CONCLUSIONS

Our finding that JL1 is expressed exclusively and stably by leukemic cells suggests that it can be used as a useful adjunctive marker for initial diagnosis and follow-up biopsy of LC, particularly in cases of scarce infiltrates.

How to interpret and pursue an abnormal complete blood cell count in adults

A complete blood cell count (CBC) is one of the most common laboratory tests in medicine. For example, at our institution alone, approximately 1800 CBCs are ordered every day, and 10% to 20% of results are reported as abnormal. Therefore, it is in every clinician's interest to have some understanding of the specific test basics as well as a structured action plan when confronted with abnormal CBC results. In this article, we provide practical diagnostic algorithms that address frequently encountered conditions associated with CBC abnormalities including anemia, thrombocytopenia, leukopenia, polycythemia, thrombocytosis, and leukocytosis. The objective is to help the nonhematologist recognize when a subspecialty consultation is reasonable and when it may be circumvented, thus allowing a cost-effective and intellectually rewarding practice.

Expression of CD45 isoforms in lymph node reactive hyperplasia

The CD45 antigen family consists of multiple molecular isoforms ranging from 180 to 220 kDa. The highest Mr isoforms are recognized by monoclonal antibodies (MoAbs) designated CD45RA, while those recognizing the low Mr isoforms are designated CD45RO. T cells expressing CD45RA are "naive" or unprimed, while those expressing CD45RO have "memory." Further, stimulation of CD45RA+ T cells induces an isoform switch to the CD45RA-/CD45RO+ phenotype. The present study examined this in vitro process by determining the in vivo CD45 isoform expression of T cells from human hyperplastic lymph nodes. Hyperplastic, as opposed to nonhyperplastic, lymph nodes exhibited the expected CD45 isoform switch from CD45RA+ to CD45RO+ T cells that has been described in vitro. The percentage of CD45RO+ T cells did not correlate with other parameters of lymphoid activation. Thus, CD45RO expression probably represents a marker of differentiation and acquisition of "memory" or late cellular activation.