A completely infarcted lymph node should alert the pathologist to the high possibility of malignant lymphoma. The lymph node lesion of infectious mononucleosis (IM) shows marked histologic diversity and occasionally may be confused with malignant lymphoma. We report a rare case of IM showing extensive lymph node infarction whose lymph node lesion was similar to lymph node infarction associated with malignant lymphoma. This case describes a 32-year-old Japanese man who had signs and symptoms consistent with IM, which he was later proven serologically to have, but whose cervical lymph node showed extensive lymph node infarction with a thin area of granulation tissue beneath the capsule. The infarcted tissue contained numerous eosinophilic ghosts of large lymphoid cells. The thin granulation tissue was composed of numerous small lymphocytes, plasma cells, and histiocytes, in addition to large lymphoid cells including immunoblasts and granulocytes. CD20, CD3, and CD45RO immunostains revealed the mixed B- and T-cell nature of the ghosts of large lymphoid cells in the infarcted tissue as well as viable large cells in the granulation tissue. The patient was free from disease after 50 months' follow-up.