Burke J S
Department of Anatomic Pathology, Alta Bates Medical Center, Berkeley, California 94705, USA.
Am J Clin Pathol. 1999 Jan;111(1 Suppl 1):S40-5.
Extranodal lymphomas are increasing in frequency owing in part to a true increase, but also as a consequence of AIDS and the recognition by pathologists that many cases formerly regarded as extranodal lymphoid hyperplasias or as pseudolymphomas are low-grade lymphomas of mucosa-associated lymphoid tissue (MALT) type. However, most primary extranodal lymphomas are aggressive lymphomas, usually of large B-cell type. Extranodal T-cell lymphomas also occur, such as the NK/T-cell lymphomas of the sinonasal area, the subcutaneous panniculitic T-cell lymphomas, and anaplastic large cell lymphomas. The aggressive lymphomas need to be distinguished from extranodal myeloid leukemias, whereas the low-grade lymphomas of MALT need to be distinguished from other extranodal lymphomas composed of small lymphocytes, such as mantle cell and follicular lymphomas. MALT lymphomas also must be differentiated from the various forms of extranodal lymphoid hyperplasia. Caution is required when determining this differentiation, since the discovery of a clonal cell population in a clinically and pathologically innocuous extranodal lymphocytic infiltrate does not necessarily equate with a diagnosis of malignant lymphoma. In this setting, a more appropriate designation might be a neoplasm or disorder of "uncertain malignant potential."
结外淋巴瘤的发病率正在上升，部分原因是其真正的发病率增加，但也归因于艾滋病，以及病理学家认识到许多以前被视为结外淋巴组织增生或假淋巴瘤的病例实际上是黏膜相关淋巴组织（MALT）型的低度淋巴瘤。然而，大多数原发性结外淋巴瘤是侵袭性淋巴瘤，通常为大B细胞型。结外T细胞淋巴瘤也会发生，如鼻窦区的NK/T细胞淋巴瘤、皮下脂膜炎样T细胞淋巴瘤和间变性大细胞淋巴瘤。侵袭性淋巴瘤需要与结外髓细胞白血病相鉴别，而MALT低度淋巴瘤则需要与其他由小淋巴细胞组成的结外淋巴瘤相鉴别，如套细胞淋巴瘤和滤泡性淋巴瘤。MALT淋巴瘤还必须与结外淋巴组织增生相鉴别。在确定这种鉴别时需要谨慎，因为在临床和病理上无害的结外淋巴细胞浸润中发现克隆性细胞群并不一定等同于恶性淋巴瘤的诊断。在这种情况下，更合适的诊断可能是“恶性潜能不确定”的肿瘤或疾病。
