Clinicopathological features of CD56+ nasal-type T/natural killer cell lymphomas with lobular panniculitis.

Nasal-type T/natural killer cell lymphoma (TNKCL) shows frequent extranodal involvement including the skin, and is associated with a poor prognosis. We have studied six patients with nasal-type TNKCL presenting with inflammatory subcutaneous nodular lesions with a subcutaneous lymphoid infiltrate. Clinical information was obtained from the medical records of the patients and at follow-up. All cases showed features of angiocentric lymphoma on histology, although there was diffuse cellular infiltration rather than an angiocentric pattern in the subcutis. All six patients were similar in immunophenotype: positive for CD56 and either cytoplasmic CD3 or CD45RO, but negative for B-cell markers and CD30. In situ hybridization using an anti-sense Epstein-Barr virus early regions probe showed a positive reaction in all cases. All patients either died with progressive disease or showed no response to combined chemotherapy. The diagnosis of nasal-type TNKCL, which has a fatal outcome, is facilitated by detection of CD56-positive tumour cells. In evaluating lobular panniculitis including apparently benign inflammatory subcutaneous nodules, nasal-type TNKCL should be considered in the differential diagnosis, especially in Asian countries.