Extranodal NK/T Cell Lymphoma Accompanied by Heavy Eosinophilic Infiltration and Peripheral Blood Eosinophilia, Involving Skeletal Muscles

ABSTRACT

The patient was a 52-year-old female with swelling in both lower legs and peripheral blood eosinophilia. Biopsy specimen revealed the heavy infiltration of eosinophils with sparse small lymphocytes showing mild atypia. The diagnosis was Kimura disease. The symptoms including eosinophilia were relieved by steroid treatment. At 17 months from initial biopsy, the patient developed swelling of the buttock. At 25 months, fever and dyspnea with multiple lung nodules developed. Wedge resection revealed multiple aggregates of CD3(+), CD56(+), Epstein-Barr virus(+) large atypical lymphocytes with necrosis. The patient was finally diagnosed with extranodal NK/T cell lymphoma (NKTL). Epstein-Barr virus in situ hybridization retrospectively performed on the previous biopsies demonstrated Epstein-Barr virus infection in small CD3(+) lymphocytes. The patient expired after 26 months despite chemotherapy. Blood eosinophilia correlated well with disease activity during the clinical course. This case shows not only unusual histologic features, which hampered the correct diagnosis, but also a unique clinical manifestation of NKTL.