To determine the appropriate early management of orbital cellulitis and the current bacterial etiology and to evaluate the clinical usefulness of orbital computed tomographic imaging for this infection, a prospective study of orbital cellulitis was conducted during a 2-year period, 1999 to 2000, after the introduction of a conservative medical management plan designed by our pediatric infectious diseases, ophthalmology and otolaryngology services. Basically patients did not have surgical intervention unless progressive involvement of the optic nerve occurred after 24 to 36 h of intravenous antimicrobial therapy. Nine patients had orbital cellulitis and subperiosteal abscesses; only one required surgical drainage because of progressive disease, this case being culture-negative. One had a blood culture positive for Streptococcus pneumoniae; conjunctival cultures showed moderate to heavy growth for S. pneumoniae from this and two other patients, but otherwise bacterial etiology could not be defined. Haemophilus influenzae was not recovered from any of their blood or conjunctival cultures. This experience, during the computed tomography scan and Haemophilus vaccine era, supports an initial medical management approach for most patients with subperiosteal or retrobulbar abscesses resulting in orbital cellulitis.

The molecular events characterizing lymphoid malignancy have been examined in an animal model system, specifically, the retroviral induction of leukemia and lymphoma in the domestic cat following infection with feline leukemia virus (FeLV). Genes differentially expressed in FeLV-induced lymphomas were isolated using a strategy of differential hybridization. Six genes were identified which demonstrate a higher level of expression in an FeLV-induced feline thymic tumor as compared with normal thymus. The differentially expressed genes encode the feline homologues of ribosomal proteins S3a, S4, S17, and L41, elongation factor-1 alpha, and cytochrome oxidase sub-unit I. Northern-blot analysis and quantification by phosphorimaging demonstrates that these genes are expressed at levels from 1.5- to 3.1-fold higher in J5-1 thymic tumor as compared with normal thymus. Expression of the selected ribosomal protein mRNA was further examined in a series of human and feline tissues, including normal tissues, malignant tumors and cell lines. Our data reveal that elevation of the selected ribosomal protein mRNA is associated with all FeLV-induced thymic lymphomas examined. The differentially expressed ribosomal protein mRNA accumulates in a balanced manner in thymic lymphomas. By contrast, the elevation in ribosomal protein mRNA levels is not associated uniformly with hematopoietic malignancy. T-lymphoid malignancy, solid tumors or actively proliferating cells. Rather, the elevation appears to be a uniform and distinctive feature of T-cell malignancy of this particular type. The elevated expression of these genes may be causally related to the neoplastic process.

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Peripheral T-cell lymphoma (PTCL) with a nodular pattern of growth is uncommon and may be misdiagnosed initially as a B-cell lymphoma or reactive process. We report a case of a rapidly growing PTCL with a distinctly nodular pattern in an axillary lymph node from an 89-year-old man. Immunohistochemical stains for CD21, CD23, and CD35 highlighted an extensive dendritic cell network that imparted the nodular appearance and, in addition, was associated intimately with the neoplastic cells. The neoplastic cells otherwise had an immunophenotype similar to previously reported cases of PTCL with a nodular pattern and germinal center origin (CD3+, CD4+, CD5+, bcl-6+, CD31+, subset CD10+, subset CXCL13+, and subset CD79a+). Molecular studies confirm a clonal T-cell receptor g gene rearrangement. This case emphasizes unusual morphologic features in a PTCL that may be mistaken for follicular lymphoma or a tumor of follicular dendritic cell origin.