title: Infectious mononucleosis lymphoadenitis showing histologic findings indistinguishable from toxoplasma lymphadenitis. A report of three cases.
abstract: Lymph node lesions in infectious mononucleosis (IM) show a marked histologic diversity. We report here three cases of IM lymphadenitis with histologic findings indistinguishable from those of toxoplasmic lymphadenitis. The histologic findings of the three cases presented here showed a histologic triad of toxoplasmic lymphadenitis, including (i) numerous lymphoid follicles with hyperplastic germinal centers; (ii) small clusters or single epithelioid histiocytes; and (iii) multiple foci of monocytoid B-cells. Moreover, all three lesions contained isolated or small clusters of epithelioid histiocytes within the hyperplastic germinal centers and the periphery of lymphoid follicles, which are the most specific histologic findings of toxoplasmic lymphadenitis. However, serologic findings confirmed EBV infection in all three cases. On in situ hybridization, numerous Epstein-Barr virus (EBV)-encoded small RNA (EBER)-positive cells were demonstrated in the germinal center, as well as in interfollicular areas in all three cases. Toxoplasmosis gondii infection was excluded in at least one case, based on serologic findings. Polymerase chain reaction analysis also demonstrated that there was no T. gondii DNA in the remaining two cases. Two of our three cases showed atypical clinical presentations, including an absence of atypical lymphocytosis in peripheral blood in two cases, age more than 30 years, and an absence of systemic symptoms in one case. It appears that previous descriptions emphasize the differential diagnostic problems between IM lymphadenitis and malignant lymphomas. However, from a therapeutic perspective, it is important to discriminate IM lymphadenitis from toxoplasmic lymphadenitis particularly in patients showing atypical clinical features.
authors.affiliation: Department of Anatomic and Diagnostic Pathology, Dokkyo Medical University School of Medicine, Mibu, Tochigi 321-0293, Japan. mkojima@dokkyomed.ac.jp
authors.forename: Masaru
authors.initials: M
authors.lastname: Kojima
authors.forename: Makoto
authors.initials: M
authors.lastname: Kashimura
authors.forename: Hideaki
authors.initials: H
authors.lastname: Itoh
authors.forename: Masahiro
authors.initials: M
authors.lastname: Noro
authors.forename: Hazuki
authors.initials: H
authors.lastname: Matsuda
authors.forename: Norihumi
authors.initials: N
authors.lastname: Tsukamoto
authors.forename: Bunshiro
authors.initials: B
authors.lastname: Akikusa
authors.forename: Nobuhide
authors.initials: N
authors.lastname: Masawa
authors.forename: Yukio
authors.initials: Y
authors.lastname: Morita
mesh_terms: D000328:Adult; D000914:Antibodies, Viral / Q000097:blood; D000956:Antigens, Viral / Q000276:immunology; D016054:DNA, Protozoan / Q000032:analysis / Q000302:isolation & purification; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D017403:In Situ Hybridization; D007244:Infectious Mononucleosis / Q000097:blood / Q000473:pathology*; D008199:Lymphadenitis / Q000097:blood / Q000382:microbiology* / Q000473:pathology*; D008297:Male; D016133:Polymerase Chain Reaction; D012367:RNA, Viral / Q000032:analysis / Q000302:isolation & purification; D014123:Toxoplasmosis / Q000473:pathology*; D055815:Young Adult
chemical_list: D000914:Antibodies, Viral; D000956:Antigens, Viral; D016054:DNA, Protozoan; D012367:RNA, Viral