Intravascular (IV) lymphomas are characterized by the presence of neoplastic lymphocytes (mostly of the B-cell lineage) restricted to the lumen of small vessels. We report an exceptional case of IV NK/T-cell lymphoma (IVNKTL) occurring in a patient with a history of extranodal NK/T-cell lymphoma, nasal-type (ENKTL).

A 64-year-old woman consulted for a recent history of asymptomatic and diffuse eruption, without B symptoms. Four years ago, she was treated for a stage I nasal ENKTL with an ongoing complete response. Clinical examination showed diffuse telangiectasia of the trunk with erythematous and telangiectatic patches/plaques of the trunk and limbs (figure). Epstein-Barr virus (EBV) viremia was present (5 log copies/ml). The histological examination of a pre-thoracic skin biopsy showed a dermal IV proliferation of large cells with a CD2+ CD3+ CD4+ CD56+/- Granzyme B+ phenotype. EBER in situ hybridization was positive, reflecting EBV infection of the neoplastic cells. These findings supported the diagnosis of IVNKTL. Staging investigations revealed bone involvement without nasal lesions. A treatment with multiple drug chemotherapy was started. However she died 1 month after.

Acquired, diffuse, eruptive and non-ascending telangiectasia can reveal viral infection, mastocytosis, monoclonal gammopathy (POEMS, TEMPI syndromes), B-cell IV lymphoma. We reported an original case of diffuse telangiectasia leading to the diagnosis of IVNKTL.
To date, 36 IVNKTL have been reported (24 men, mean age of 50 years):

1. Similarly to ENKTL, the diagnosis of IVNKTL is based on (1) a neoplastic cell proliferation, (2) of NK/T-cell phenotype (CD2+ CD56+), (3) expressing cytotoxic proteins (TIA-1, granzyme B, perforine) with (4) EBV infection. However, this proliferation is confined to the lumina of vessels in IVNKTL whereas it takes place in the extravascular tissue in case of ENKTL,
2. IVNKTL involved mostly the skin (26/36), followed by the central nervous system (8/36), lung (4/36), liver and bone (2/36), heart, spleen, testicles, ileum and kidney (1/36),
3. The skin involvement presented as erythematous patches/plaques (n=26) sometimes hyperpigmented (n=4) or purpuric (n=2); nodules (n=4) or ulceration (n=1). The lesions were mostly multiple (n=24) and were strictly localised on the trunk (n=7), lower limbs (n=10) or were diffuse (n=9). Presence of telangiectasia on the plaques was noted in 2 cases,
4. The prognosis is poor with a 1-year survival rate of 32%.

Only 2/ 36 IVNKTL were associated with ENKTL. We reported the third case. The occurrence of these two rare and closely related entities in the same patient suggests a common origin (IV relapse of the ENTKL). However, in the absence of available clonality analysis, the hypothesis of 2 different EBV-related lymphoproliferations remains possible.