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Extranodal natural killer cell/T-cell lymphoma, nasal type
Lethal midline granuloma
Malignant midline reticulosis [OBS]
Malignant reticulosis, NOS [OBS]
NK-/T-cell lymphoma, nasal and nasal-type
Polymorphic reticulosis [OBS]
Predominantly extranodal, characterized by a broad morphologic spectrum. The infiltrate is often angiocentric, with prominent necrosis and vascular destruction. It is designated NK/T (rather than NK) because while most cases appear to be NK cell neoplasms, (EBV+ CD56+), rare cases show EBV+ CD56- cytotoxic T-cell phenotype.
Extranodal NK/T cell lymphoma almost always shows an extranodal presentation. The upper aerodigestive tract (nasal cavity, nasopharynx, paranasal sinuses, palate) is the most commonly involved, with the nasal cavity being the prototypic site of involvement. Preferential sites of extranasal involvement include the skin, soft tissue, GI tract, and testis. Some cases may be accompanied by secondary LN involvement. Rare examples of primary LN disease in the absence of extranodal involvement have been reported. Patients with nasal involvement present with symptoms of nasal obstruction or epistaxis due to the presence of a mass lesion or with extensive midfacial destructive lesions. The lymphoma can extend to adjacent tissues such as the nasopharynx, paranasal sinuses, orbit, oral cavity, palate, and oropharynx. The disease is often localized to the upper aerodigestive tract at presentation, and bone marrow involvement is uncommon.
Extranasal NK/T-cell lymphomas have variable presentations depending upon the major site of involvement. Skin lesions are commonly nodular, often with ulceration; intestinal lesions often manifest as perforation. Other involved sites often present with mass lesions, commonly in late stage of disease with involvement of multiple extranodal sites. LN can be involved as part of disseminated disease. BM and PB involvement can occur.
The prognosis for nasal extranodal NK/T-cell lymphoma is variable, historically 30-40%, but survival has improved in recent years with more intensive therapy including radiotherapy.
Extranasal extranodal NK/T-cell lymphoma is highly aggressive with a short survival time and poor response to therapy.
Definitive Diagnostic Methods
T-cell receptor and immunoglobulin genes are in germline configuration in most cases
T-cell receptor genes show clonal rearrangement in small proportion of cases