Original ArticlesPostchemotherapy Histiocyte-rich Pseudotumor Mimicking Residual Lymphoma A Report of 11 Cases Correlating Clinicopathologic and Radiologic FindingsFang, Hong MD*; Chuang, Hubert H. MD†; Strati, Paolo MD‡,§; Hu, Shimin MD, PhD*; Shuai, Wen MD*; Medeiros, L. Jeffrey MD*; Wang, Wei MD, PhD* Author Information Departments of *Hematopathology †Nuclear Medicine ‡Lymphoma and Myeloma §Translational Molecular Pathology, The University of Texas MD Anderson Cancer Center, Houston, TX W.W. and L.J.M.: designed the study. H.F.: wrote the manuscript. H.H.C., P.S., S.H., and W.S.: collected data and performed analysis. Conflicts of Interest and Source of Funding: The authors have disclosed that they have no significant relationships with, or financial interest in, any commercial companies pertaining to this article. Correspondence: Wei Wang, MD, PhD, Department of Hematopathology, Unit 72, The University of Texas MD Anderson Cancer Center, 1515 Holcombe Boulevard, Houston, TX 77030 (e-mail: [email protected]). The American Journal of Surgical Pathology: February 2021 - Volume 45 - Issue 2 - p 160-168 doi: 10.1097/PAS.0000000000001547 Buy Metrics Abstract Postchemotherapy histiocyte-rich pseudotumor is a rare event in lymphoma patients and can cause elevated metabolic activity on positron emission tomography-computed tomography scan mimicking residual tumor. Here, we reported 11 lymphoma cases showing mass-like lesions with increased fluorodeoxyglucose uptake after chemotherapy. These postchemotherapy lesions occurred in various anatomic sites including spleen, mediastinum, lymph node, and other tissue locations, concerning for refractory or residual lymphoma. Their median size was 2.7 cm (range, 1.4 to 7.7 cm) and the median standardized uptake value on positron emission tomography-computed tomography was 10.6 (range, 5.2 to 13.8). Histologic examination of these lesions demonstrated reactive changes mainly composed of histiocyte-rich proliferation without viable lymphoma. Fat necrosis, cholesterol cleft, and calcium deposit were also commonly observed. After biopsies, 3 patients received additional chemotherapy, 2 had stem cell transplant with adjuvant chemotherapy or radiation, 1 had surgical excision, and the remaining 5 patients did not receive any further treatment. Follow-up imaging studies showed the resolved or decreased fluorodeoxyglucose activities in all patients including those without additional treatments, consistent with benign/reactive nature of these pseudotumor lesions. This study illustrates postchemotherapy mass-like lesions with elevated metabolic activity do not always represent residual disease and provides awareness of correlation between radiologic and histologic features of these lesions to avoid misinterpretation and overtreatment of lymphoma patients after chemotherapy. Copyright © 2020 Wolters Kluwer Health, Inc. All rights reserved.