A Case of Nasal Extranodal NK/T-cell Lymphoma of Lower Limb Muscle Revealed by 18F-FDG PET/CT.

BACKGROUND: Extranodal NK/T-cell lymphoma (ENKTCL) is a type of malignant non-Hodgkin's lymphoma originating from mature T cells and NK cells, mainly involving the upper aerodigestive tract, including the nasal cavity, nasopharynx, oropharynx, oral cavity, hypopharynx, larynx, and occasionally the skin, salivary glands, testes, and gastrointestinal tract, but rarely the skeletal muscle.

CASE PRESENTATION: An 82-year-old man presented with redness, swelling, and pain in his right lower limb for 3 months. He was initially diagnosed with cellulitis at another hospital and was treated conservatively for two weeks without improvement. He underwent a biopsy of the lesioned muscle and histopathology revealed nasal type ENKTCL. 18F-FDG PET/CT was recommended for the staging of the lymphoma, and the results showed that except for the muscles of the right lower extremity, no other organs and tissues were involved.

CONCLUSION: ENKTCL confined to the muscle of the lower extremity is rare and often initially misdiagnosed as myositis because of red, swollen, heat, and painful symptoms that resemble inflammation, and in it, higher radiotracer uptake in 18F-FDG PET/CT helps to distinguish it from myositis.