Clinical features

•Aggressive with high mortality

•Extranodal NK/T cell lymphoma, nasal type & aggressive NK-cell leukemia

•Most commonly affects the nasal cavity & upper aerodigestive tract

•Predominantly seen in Chinese, Korean & Japanese populations; rare in Europeans

•Cutaneous involvement may co-exist with nasal lesions or represent the primary site

•Skin lesions include often ulcerated nodules & plaques, vasculitic lesions, panniculitis & cellulitis-like lesions

•Predilection for trunk & limbs

•B symptoms

•Hemaophagocytosis syndrome

Histological features

•Associated with EBV

•Immunosuppression

•Mutation of genes in JAK/STAT pathway

•Variable ulceration & Pseudoepitheliomatous hyperplasia

•Exceptional epidermal involvement

•Dense nodular or diffuse infiltrate of small to large atypical lymphocytes

•Frequent mitoses

•Angiotropism, angiodestruction, thrombi & coagulative necrosis

•Background inflammatory cells

•NK variants- CD2, CD56, CD43, CD45RO & CD3e

•TIA-1, granzyme B & perforin +ve

•CD2, CD4, CD5, CD7 & CD8 –ve

•Germline TCR

•T-cell lineage may be seen in up to 40% of cases with variable expression of T-cell markers, cytotoxic markers and monoclonal TCR

Differential diagnosis

Lymhomatoid granulomatosis is also associated with EBV and an angiocentric/angiodestructive infiltrate but is a B-cell lymphoma with associated reactive T-cells. Other lymphomas which may demonstate angioinvasion & angiodestruction including γ/δ T-cell & subcutaneous panniculitis-like T-cell lymoma may be excluded with IHC & insitu hybridization for EBV.