Small lymphoid proliferations in extranodal locations.
BACKGROUND
Low-grade non-Hodgkin lymphomas frequently involve extranodal sites including the gastrointestinal tract, skin, and lung, either selectively or as part of widespread dissemination. Differentiation from inflammatory or infectious conditions requires knowledge of specific histologic characteristics of the various entities as well as ancillary techniques.


OBJECTIVE
To describe the key features and provide diagnostic clues to the identification of specific extranodal low-grade lymphomas of T-cell and B-cell types including small lymphocytic lymphoma, follicular lymphoma, mantle cell lymphoma, extranodal marginal zone B-cell lymphomas of mucosal-associated lymphoid tissue, and hairy cell leukemia. Histologic and cytologic features are highlighted, as well as appropriate integration of results of ancillary diagnostic studies including flow cytometry, immunohistochemistry, molecular features, and cytogenetics.


METHODS
The published literature as well as personal experience from a specialized hematopathology practice at a large university medical center.


CONCLUSIONS
Correct identification of extranodal low-grade lymphomas and differentiation from hyperplastic and inflammatory or infectious processes require the ability to distinguish each of the specific entities discussed. Ancillary studies are often indispensable in reaching a correct diagnosis.
Rao
Dinesh S
DS
Center for Health Sciences, UCLA, Department of Pathology and Laboratory Medicine, 10833 Le Conte Ave, Los Angeles, CA 90095, USA.
Said
Jonathan W
JW
D049109:Cell Proliferation; D003937:Diagnosis, Differential; D005770:Gastrointestinal Neoplasms / Q000473:pathology; D006801:Humans; D007239:Infections / Q000473:pathology; D007249:Inflammation / Q000473:pathology; D008228:Lymphoma, Non-Hodgkin / Q000473:pathology*; D013601:T-Lymphocytes / Q000166:cytology