Extranodal nasal/nasal type NK/T cell lymphoma

EXTRANODAL NASAL/NASAL TYPE NK/T CELL LYMPHOMA (the most common and well characterized NK-cell neoplasm^{ref1,
ref2,
ref3,
ref4,
ref5,
ref6,
ref7,
ref8,
ref9,
ref10,
ref11,
ref12}).

nasal lymphomas : approximately 10-20% also have skin involvement.
"nasal-type" lymphomas show the same histologic features but arise from extranasal sites such as :

skin (many) occur more often in females, have a higher frequency of a T-cell rather than a NK-cell phenotype and less association with EBV^ref1,
ref2
gastrointestinal tract
testis
kidney
upper respiratory tract
rarely the eye/orbit^{ref1,
ref2,
ref3,
ref4,
ref5,
ref6}.

Although the cell of origin is a NK cell in 80% of cases, particularly in patients in the Far East, central and South America and in native Americans, 10-30% of cases arise from cytolytic T cells (NK-like T cells that express CD56 and TIA-1; gd > aß type^{ref1,
ref2,
ref3}). Hence, the designation nasal and nasal type NK/T-cell lymphoma. It should be noted that 35-55% of nasal tumors overall have a B cell phenotype^ref1,
ref2. Lymphomas involving the sinuses without nasal lymphoma are predominantly diffuse large B-cell lymphoma (DLBCL)

, whereas lymphomas involving the nasal cavity alone are predominantly NK/T-cell lymphomas^ref.
Epidemiology : more commonly occurs in Asia and Latin America. The disease occurs more commonly in males, and the median age is 50–55 years^ref1,
ref2 (Chan JK. Peripheral T-cell and NK-cell neoplasms: an integrated approach to diagnosis. Mod. Pathol. 1999;12:177–99)
Aetiology : HHV-4 / EBV

is present in the majority (80-100%) of nasal NK/T-cell lymphomas and less often in nasal type NK/T-cell lymphomas (15-40% or more in some series)^{ref1,
ref2,
ref3,
ref4}
Symptoms & signs : nasal obstruction, nasal discharge, and epistaxis. The disease may present with facial swelling or midfacial/destructive disease and was formerly called lethal midline granuloma. Nasal NK/T lymphoma is localized stage I/II in 80% of patients at diagnosis but can disseminate early to skin, gastrointestinal tract, testis, orbit and central nervous system (CNS)
Laboratory examinations :

cytomorphology : tumor cells in nasal/nasal type NK/T-cell lymphoma can be a mixture of small, medium or large cells, but most are large dysplastic cells with hyperchromatic or vesicular chromatin. Admixed inflammatory cells may be numerous. Zonal necrosis is prominent. Angiodestructive lesions are present in most (> 60%) but not all cases.
immunophenotype : CD2⁺, CD3^-, CD16^-/+, CD56⁺, CD57^- phenotype

Therapy : although radiation alone can achieve complete remission in approximately two-thirds of localized disease, local relapse occurs in half the patients and systemic progression develops in one quarter of patients^ref. Combined modality therapy is recommended, and CNS prophylaxis should be considered.
Prognosis is variable with long-term survival of 20-35%^ref1,
ref2, primarily in stage I, non-bulky disease. Some studies have reported survivals above this range (up to 80%); however, inclusion of CD56^– and EBV^– cases or lack of reporting of immunophenotyping may have resulted in the inclusion of more favorable lymphomas. Systemic progression is usually fatal^ref1,
ref2. Nasal-type NK/T cell lymphoma has a worse prognosis that those originating in the nasal region due to disseminated extranodal disease, including skin, gastrointestinal tract, soft tissue, and testis^ref. Only 20% of patients have stage I disease^ref. Despite anthracycline therapy, median survival is < 1 year^ref. Patients with cutaneous only involvement have a better survival^ref.

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