Lethal midline granuloma: report of three cases.

Lethal midline granuloma (LMG) is a rare clinical entity characterized by progressive relentless ulcerations and necrosis of midfacial structures. It occurs more frequently in Oriental than in Western populations with no demonstrable etiology. Treatment and outcome for cases differ, but their pathological distinction may not always be possible from routine biopsy specimens. The histological features often seen include widespread coagulative necrosis, heavy inflammatory infiltrates, and atypical pleomorphic cells. However, the paucity of these atypical cells in biopsy specimens and the degree of necrosis can make the diagnosis of a neoplastic lesion very difficult. Because of the progress in pathology methodology including immunohistochemistry, most cases have been proven to be malignant lymphomas of T-cell lineage. We present 3 patients for whom an initial clinical diagnosis of LMG was made. From their several oral biopsies and nasal specimens, difficulties were encountered in differentiating "midline granuloma" from other possible diseases using histomorphological criteria alone. After extensive evaluations, malignant T-cell lymphoma was the specific disease entity identified in only one case by cell membrane immunostaining technique. A literature review was carried out, and recent concepts of the etiology and pathogenesis of this disease are presented.