AIDS-associated B-cell non-Hodgkin's lymphoma masquerading as a cutaneous T-cell neoplasm: an aberrant immunophenotype requiring comprehensive analysis for lineage resolution

CD3-positive large B-cell lymphoma

It is not uncommon for some B-lineage non-Hodgkin lymphomas (NHLs) to aberrantly coexpress T-cell markers, particularly CD5, as well as CD7, CD2, CD4, and/or CD8 in rare cases. Cases of CD3-positive B-cell NHL, however, have not previously been described in the literature. We present 4 cases of large B-cell lymphoma aberrantly coexpressing T-cell marker CD3 and B-lineage markers as well as demonstrating clonal rearrangement of the immunoglobulin genes but not the gamma T-cell receptor gene. To our knowledge, this represents the first series report of B-cell NHL coexpressing T-lineage-specific marker CD3. The identification of such cases indicates that the use of CD3 antibody alone in paraffin sections may lead to an incorrect determination of cell lineage in some B-cell NHL. Immunohistochemistry using additional cell lineage specific markers or molecular analysis for antigen receptor gene rearrangements are necessary for correct determination of the cell lineage in such cases.

Histopathologic, Immunohistochemical, and Cytologic Analysis of Feline Myeloma-Related Disorders: Further Evidence for Primary Extramedullary Development in the Cat

Feline myeloma-related disorders (MRD) are rare neoplasms of plasma cells. The multistep transformation model of myeloma in humans is based on the premise that plasma cells undergo neoplastic transformation primarily within the intramedullary compartment and that over time they become poorly differentiated and metastasize to extramedullary locations. Historically, diagnostic criteria used for human multiple myeloma have been applied to the cat, with the assumption that feline MRD commonly arises in the intramedullary compartment. Our objectives were to describe the features of feline MRD confirmed by cytology, histopathology, histochemistry, and immunohistochemistry and to categorize these tumors. A priori hypotheses were 1) tumor category predicts survival and 2) cats with well-differentiated tumors commonly have extramedullary involvement in contrast to human myeloma patients. This multicenter, retrospective study identified 26 MRD cases. There was good agreement between histopathologic and cytologic tumor categorization. Histochemistry and immunohistochemistry were shown to be valuable adjunct tests in the diagnosis of MRD. Cats with well-differentiated tumors had increased median survival relative to those with poorly differentiated tumors (254 versus 14 days). We have reported that marked extramedullary involvement at initial clinical presentation is significantly more common in the cat than in human MRD patients. In this study, we demonstrate that cats with well-differentiated tumors more commonly have extramedullary involvement than human myeloma patients with well-differentiated tumors (90% versus 20%, P < 0.0002). These results contrast strongly with the human myeloma model of primary intramedullary neoplastic transformation and suggest that primary extramedullary neoplastic transformation may be more common in feline MRD.

Cutaneous CD8 T cell infiltrates in advanced HIV infection

BACKGROUND

Aggressive non-Hodgkin's lymphomas are common among patients infected with HIV. Although such lymphomas are mostly of the B-cell type, various cases of cutaneous T-cell lymphoma (CTCL) have also been reported. Recent reports suggest that some HIV-related lymphoproliferative conditions may not be clonal processes, but polyclonal lymphoid proliferations.

OBJECTIVE

We reviewed our experience with HIV patients seen at the dermatology clinics for possible CTCL.

METHODS

A retrospective study was performed to evaluate clinical, laboratory, and histologic findings of HIV-infected patients with atypical T-cell cutaneous infiltrates.

RESULTS

We observed 9 patients with advanced HIV infection and a cutaneous eruption characterized by a dense infiltrate of lymphocytes resembling mycosis fungoides histopathologically, but composed of CD8(+) cells. Although clonality was not identified in any of the 6 cases tested, 3 patients had similar CD8(+) infiltrates involving lymph nodes or bone marrow. Of the 9 patients, 8 died of AIDS wasting syndrome or infections in less than 1 year.

CONCLUSION

Cutaneous and systemic infiltrates with polyclonal CD8 T lymphocytes can be seen in patients with advanced HIV infection and profound CD4 lymphopenia. The clinical presentation may resemble CTCL and is associated with a poor outcome.