Affiliations of authors: Hematology Branch, National Heart, Lung and Blood Institute (RS, YT, RWC); Urologic Oncology Branch, National Cancer Institute (RS); Laboratory of Pathology, National Cancer Institute (AF), Warren Magnusson Grant Clinical Center, National Institutes of Health (JR, RC, CC, A FS); and Surgery Branch, National Cancer Institute (DSS), Bethesda, MD
Correspondence to: Richard W. Childs, MD, Hematology Branch, National Heart, Lung and Blood Institute, 10 Center Dr., Bldg. 10/CRC-35330, Bethesda, MD 20892 (e-mail: childsr{at}nhlbi.nih.gov).
Positron emission tomography (PET) has gained favor as an imaging modality to assess tumor extent and response to chemotherapy and to predict the risk of disease relapse in patients with Hodgkin disease and non-Hodgkin lymphoma (15). Although PET is highly sensitive for diagnosing relapsed lymphomas, the following case from our institution demonstrates that PET positivity does not always imply disease recurrence. A 14-year-old girl with stage III-B diffuse large B-cell lymphoma achieved a complete remission after being treated with cyclophosphamide, doxorubicin, etoposide, prednisone, cytarabine, bleomycin, vincristine, methotrexate, and leucovorin (ProMACE-CytaBOM) chemotherapy. A computed tomography (CT) scan 3 months after the patient completed chemotherapy revealed recurrent mediastinal adenopathy and new lung nodules; lymphoma relapse was confirmed by thoracoscopic lung biopsy. The thoracoscopy was complicated by a pneumothorax and a recurrent left-sided pleural effusion, both of which resolved after the patient underwent talc pleurodesis. The patient received salvage chemotherapy, and follow-up staging studies (CT scans and whole-body gallium and PET scans) revealed that she had achieved a second complete response. She then received an investigational allogeneic hematopoietic cell transplant (HCT) from her human leukocyte antigenidentical brother after reduced intensity conditioning with cyclophosphamide and fludarabine. She was subsequently discharged from the hospital and remained in complete response 100 days after the transplant.
The patient returned to our facility 3 years after her transplant for routine restaging studies. She denied having any B symptoms, and her physical examination, bone marrow biopsy, and blood analyses were normal. CT scans revealed no evidence of recurrent lymphadenopathy; multiple left-sided pleural-based masses remained unchanged compared with those detected by CT scans performed after pleurodesis and immediately before HCT (Fig.1, a). However, a PET scan (Fig. 1, b) now showed intense metabolic activity in the pleural-based nodules that was suggestive of lymphoma relapse. A subsequent CT-guided fine-needle aspiration biopsy of a left pleural mass revealed no histopathologic evidence of lymphoma; instead, a granulomatous background with numerous polarizable foreign bodies in multinucleated giant cells (Fig. 1, c) established a diagnosis of talc granulomas. The patient remains well and in complete remission more than 4
years after transplantation.
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This case report highlights the importance of considering the possibility that patients who have undergone talc pleurodesis may develop talc granulomas that produce a false-positive PET scan. Histologic or cytologic examination of pleural abnormalities remains the only method to determine whether a positive PET scan is the consequence of malignancy versus a benign inflammatory process, such as a talc-induced granuloma. The time interval required for talc-induced pleural granulomas to resolve is unclear. This case, as well as one reported previously (7), demonstrates that metabolically active granulomas that mimic a tumor relapse on PET scans may persist for years after talc pleurodesis. Therefore, it is important for oncologists to be aware that talc pleurodesis might result in metabolically active pleural granulomas that would diminish the specificity of PET scans obtained for tumor restaging.
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