CD123 immunostaining patterns in systemic mastocytosis: differential expression in disease subgroups and potential prognostic value.

CD123 is the α-subunit of the interleukin-3 receptor; it represents a potential therapeutic target in systemic mastocytosis (SM) given its absent expression on normal/reactive mast cells (MCs) and aberrant expression on neoplastic MCs. We studied 58 SM patients to define CD123 expression patterns by immunohistochemistry and its clinical significance. Two hematopathologists independently scored bone marrow slides using predefined histologic parameters. In all, 23 patients had indolent SM (ISM), 10 aggressive SM (ASM), 23 SM with associated hematological neoplasm (SM-AHN) and 2 had mast cell leukemia (MCL). MC_CD123 expression was demonstrable in 37 (64%) cases; expression rates were 100%, 61%, 57% and 0% in ASM, ISM, SM-AHN and MCL, respectively (P=0.02). Focal proliferation of plasmacytoid dendritic cells (PDCs) around MC aggregates, suggesting a tumor-promoting role for PDCs, was noted in 44 (76%) cases, and was significantly higher in CD123-positive versus -negative cases (87% versus 50%, P=0.005). CD123 expression and its staining intensity had prognostic value in SM-chronic myelomonocytic leukemia and nonindolent SM patients, respectively. These observations suggest that targeting CD123 in SM may have direct (via MCs) and indirect (via PDCs) antitumor effects and clinical trials to that effect require laboratory correlative studies to address the observed target expression heterogeneity.

Recurrent translocations involving the IRF4 oncogene locus in peripheral T-cell lymphomas.

Oncogenes involved in recurrent chromosomal translocations serve as diagnostic markers and therapeutic targets in hematopoietic tumors. In contrast to myeloid and B-cell neoplasms, translocations in peripheral T-cell lymphomas (PTCLs) are poorly understood. Here, we identified recurrent translocations involving the multiple myeloma oncogene-1/interferon regulatory factor-4 (IRF4) locus in PTCLs. IRF4 translocations exist in myeloma and some B-cell lymphomas, but have not been reported earlier in PTCLs. We studied 169 PTCLs using fluorescence in situ hybridization and identified 12 cases with IRF4 translocations. Two cases with t(6;14)(p25;q11.2) had translocations between IRF4 and the T-cell receptor-alpha (TCRA) locus. Both were cytotoxic PTCLs, unspecified (PTCL-Us) involving bone marrow and skin. In total, 8 of the remaining 10 cases were cutaneous anaplastic large-cell lymphomas (ALCLs) without TCRA rearrangements (57% of cutaneous ALCLs tested). These findings identified IRF4 translocations as a novel recurrent genetic abnormality in PTCLs. Cytotoxic PTCL-Us involving bone marrow and skin and containing IRF4/TCRA translocations might represent a distinct clinicopathologic entity. Translocations involving IRF4 but not TCRA appear to occur predominantly in cutaneous ALCLs. Detecting these translocations may be useful in lymphoma diagnosis. Further, due to its involvement in translocations, MUM1/IRF4 protein may play an important biologic role in some PTCLs, and might represent a possible therapeutic target.

Overexpression of Syk tyrosine kinase in peripheral T-cell lymphomas.

Peripheral T-cell lymphomas (PTCLs) are fatal in the majority of patients and novel treatments, such as protein tyrosine kinase (PTK) inhibition, are needed. The recent finding of SYK/ITK translocations in rare PTCLs led us to examine the expression of Syk PTK in 141 PTCLs. Syk was positive by immunohistochemistry (IHC) in 133 PTCLs (94%), whereas normal T cells were negative. Western blot on frozen tissue (n=6) and flow cytometry on cell suspensions (n=4) correlated with IHC results in paraffin. Additionally, western blot demonstrated that Syk-positive PTCLs show tyrosine (525/526) phosphorylation, known to be required for Syk activation. Fluorescence in situ hybridization showed no SYK/ITK translocation in 86 cases. Overexpression of Syk, phosphorylation of its Y525/526 residues and the availability of orally available Syk inhibitors suggest that Syk merits further evaluation as a candidate target for pharmacologic PTK inhibition in patients with PTCL.

HIV infection and lymphoma.

The incidence of lymphoma in patients with HIV infection greatly exceeds that of the general population. The increased risk for lymphoma appears related to multiple factors, including the transforming properties of the retrovirus itself, the immunosuppression and cytokine dysregulation that results from the disease, and, most importantly, opportunistic infections with other lymphotrophic herpes viruses such as Epstein-Barr virus and human herpesvirus 8. Histologically lymphomas fall into three groups: (1) those also occurring in immunocompetent patients; (2) those occurring more specifically in HIV-positive patients; and (3) those also occurring in patients with other forms of immunosuppression. Aggressive lymphomas account for the vast majority cases. They frequently present with advanced stage, bulky disease with high tumour burden and, typically, involve extranodal sites. Clinical outcome appears to be worse than in similar aggressive lymphomas in the general population. However, following the introduction of highly active antiretroviral therapy, the risk for developing lymphoma in the context of HIV infection has decreased and the clinical outcome has improved.

Subcutaneous granuloma annulare in childhood: clinicopathologic features in 34 cases.

OBJECTIVE: To gather clinicopathologic data on subcutaneous granuloma annulare (SGA), a subtype of granuloma annulare that occurs exclusively in children and is histologically similar to rheumatoid nodules. DESIGN: Retrospective record review. PATIENTS: Children <10 years old in whom SGA, deep granuloma annulare, or necrobiotic granuloma was diagnosed at the Mayo Clinic (Rochester, MN) from 1983 to 1998. RESULTS: Thirty-four patients (21 girls and 13 boys; average age at diagnosis: 4.6 years) were found to have SGA. The lesions predominantly occurred in the lower extremity, especially in a pretibial location. Local recurrence within 1 month to 7 years was documented in 38.2%; recurrence at other locations was documented in 14.7%. Average follow-up was 60 months; during follow-up, no patients developed signs or symptoms of rheumatologic disease. Insulin-dependent diabetes mellitus was diagnosed in 2 patients, 1 before the development of SGA and 1 after it by 1 month. CONCLUSIONS: SGA is a lesion that presents as subcutaneous nodules on the lower extremities, hands, or scalp in young children. Recurrence is common but usually does not warrant additional biopsy.

Death from inappropriate therapy for Lyme disease.

A 30-year-old woman died as a result of a large Candida parapsilosis septic thrombus located on the tip of a Groshong catheter. The catheter had been in place for 28 months for administration of a 27 month course of intravenous cefotaxime for an unsubstantiated diagnosis of chronic Lyme disease.