NASAL-TYPE T/NK-CELL LYMPHOMA (ANGIOCENTRIC LYMPHOMA)
Nasal-type T/NK-cell lymphomas are common in Asia and in parts of Latin America but rare in the United States and in Europe. This may reflect an ethnic predisposition for the disease. Children may be effected as well as adults. Most studies have shown a male-to-female ratio of 2:1 to 3:1.
This neoplasm most commonly presents in the nasal cavity, but may involve the entire upper aerodigestive tract down to the larynx. The skin, soft tissue, gastrointestinal tract and testes may be secondarily involved. Lung involvement is not seen.
Clinically, patients present with ulcerative destructive lesions of the midline face. The course of the disease is usually aggressive, with a large number of Asian studies reporting a median survival of 6 to 25 months. Several American and European studies have shown similar results. A recent small series by Ferry et al. of 17 patients with nasal-type T/NK lymphomas demonstrated 73% survival at last follow-up (median follow-up 10 years). Nearly all of the patients had stage I disease. Localized disease is sensitive to radiation therapy, but once dissemination occurs, prognosis is poor. Some patients may go on to develop a hemophagocytic syndrome which has a rapidly progressive course and may be responsible for some deaths.
Morphologically, the disease consists of a polymorphic lymphoid population with a broad cytologic spectrum. The neoplastic cells may range from small and slightly atypical to large cells with oval to convoluted nuclei and nucleoli. Many of the cells show a distinct rim of clear cytoplasm. Admixed neutrophils, plasma cells and histiocytes are often seen. This inflammatory background may be prominent, especially in low grade lesions. Necrosis is a prominent feature in nasal-type T/NK-cell lymphomas, often extensive and associated with vascular thromboses.
Vascular invasion and destruction is commonly seen, hence the term "angiocentric lymphomas" previously used to describe these lesions. The characteristic feature is invasion of vascular walls by neoplastic lymphoid cells often with thrombosis and luminal occlusion. The vascular occlusion is usually associated with prominent coagulative necrosis and karyorrhectic debris as previously mentioned. Although usually present, angioinvasion is not required for a diagnosis of nasal-type T/NK-cell lymphoma.
Most cases are CD2+, CD45RO+, CD43+ , CD56+, CD5-/+, and CD7+/-. Surface CD3 expression is typically absent, but cytoplasmic CD3 may be identified. Although usually strongly CD56+, these lymphomas are negative for other NK cell associated antigens such as CD16 and CD57. The cells may be positive for CD4 or CD8 and are negative for TCRb and TCRg gene rearrangements. Virtually all cases demonstrate Epstein Barr virus-encoded RNA (EBER) by in-situ hybridization.
The differential diagnosis includes blastic or monomorphic NK-cell leukemia/lymphoma. These tumors are typically negative for CD2 and EBER. They closely resemble acute myeloid leukemia and may express CD56. Lymphomatoid granulomatosis (LYG) is a similar lesion and is considered to be part of the same disease spectrum (angiocentric immunoproliferative lesions). However, most cases of LYG are EBER positive B-cell neoplasms with a prominent T-cell reaction. The pattern of necrosis and vascular invasion is similar in both tumors, however, LYG tends to involve the kidney and central nervous system, sites rarely involved with nasal type T/NK-cell lymphoma.
Contributed by Melissa Halpern, MD