NK cell lymphoblastic lymphoma in the masticator space: a case of non-Hodgkin lymphoma with challenging maxillofacial manifestation and immunophenotype.

Clinical and pathologic findings in extranodal non-Hodgkin lymphoma (NHL) often raise challenging problems in diagnosis. We demonstrate the first established case of lymphoma with precursor natural killer (NK) cell origin in the oral and maxillofacial region. An 81-year-old Japanese man had an enlarged facial mass mainly in the parotid region but hyposensitivity in the affected side of the mental and lingual region, and diagnostic imaging revealed the origin to be in the masticator space and indicated an advanced-stage lymphoma. The tumor cell immunophenotype was CD56(+)CD3(-)CD4(-), with no B-cell- or myeloid-associated markers. The genotype was of the germ-line configuration of T-cell receptor genes, and no association with Epstein-Barr virus was evident, leading to a diagnosis of NK-cell lymphoblastic lymphoma. This report discusses diagnostic challenges of NHL, including manifestation of numb chin syndrome as a clinical indicator and immunophenotyping of NK-cell-lineage neoplasms.