Heterogeneous bone marrow uptake on interim (18)F-fluorodeoxyglucose positron emission tomography for lymphoma mimicking disease progression: a case report

INTRODUCTION: The use of (18)F-fluorodeoxyglucose positron emission tomography ((18)F-FDG PET) scanning for baseline staging and assessment of treatment response for higher grade lymphomas is considered to be the standard of care. Evaluation of lymphomatous bone marrow infiltration on (18)F-FDG PET can usually distinguish between normal regenerating marrow following chemotherapy by a characteristic pattern of uptake. CASE PRESENTATION: Here we report the case of a 51-year-old Caucasian woman with mixed low- and high-grade lymphoma with biopsy confirmed marrow infiltration. An interim post-three cycle chemotherapy (18)F-FDG PET scan revealed apparent progression of marrow disease. Subsequent investigations were performed including bone marrow biopsies, repeat (18)F-FDG PET scanning and a white cell scan. These revealed the interim (18)F-FDG PET scan appearance was due to a highly unusual pattern of scattered islands of regenerating normal marrow, rather than progressive lymphoma. CONCLUSIONS: Our case report highlights that apparent severe bone marrow abnormalities on (18)F-FDG PET scans in lymphoma patients treated with chemotherapy are not always due to disease. Clinicians should retain a high index of suspicion for benign causes when (18)F-FDG PET scan results appear incongruent with clinical response.