Background: The Working Formulation commonly used to classify NHL in Thailand has been recognized as imperfect for
primary extranodal lymphoma, especially in head and neck regions.
Objective: To study the clinicopathological and immunohistochemical features of extranodal malignant lymphoma of the upper aerodigestive tract according to WHO classification.
Setting: King Chulalongkorn Memorial Hospital.
Design: Descriptive study.
Patients: 77 Thai patients who presented between 1998 and 2003.
Methods: Routine histology was performed and stained with H&E and immunohistochemistry, and clinical characteristics
were recorded.
Results: The patients included 42 males and 35 females, with an average age of 53.87years. Tumor sites were as follows:
Waldeyer’s ring (n = 42, 54.55%), sinonasal areas (n = 19, 24.67%), oral cavity (n = 9, 11.69%), hypopharynx (n = 4,
5.19%), and larynx (n = 3, 3.90%). Immunohistochemically, 57 tumors (74.02%) were of B-cell phenotype and 19 tumors (24.68%) were of T-cell phenotype. According to the WHO classification, 45cases (58.43%) were large B-cell, 3 (3.90%)
were Burkitt, 3 (3.90%) were marginal zone B-cell lymphomas of mucosa-associated lymphoid tissue (MALT), 4 (5.19%) were follicular lymphoma, 1 (1.30%) was precursor B-lymphoblastic lymphoma, and 1 (1.30%) were mantle cell lymphoma.
Among the T-cell lymphomas, 9 (11.69%) were of peripheral T-cell lymphoma, unspecified, 9 (11.69%) were extranodal NK/T cell lymphoma, nasal type, and 1 (1.30%) were anaplastic large-cell lymphomas. In nasal cavity, 8 tumors (42.11%)
were extranodal NK/T-cell lymphoma, nasal type, 5 (26.32%) were diffuse large B-cell lymphoma, 4 (21.05%) were peripheral T-cell lymphoma, unclassified, and 1 (5.26%) was Burkitt lymphoma.
Conclusion: Our data correspond with series from Japan, Hong Kong, and Korea, but there is a significant difference from Western population in T-cell lymphomas of sinonasal area especially extranodal NK/T cell lymphoma of nasal type and peripheral T-cell lymphoma, unspecified which had a higher frequency in Thailand, Japan, Hong Kong, and Korea.

Keywords: Lymphoma, Upper aerodigestive tract, WHO classification, Extranodal, Thai