Diagnostic Tissue Re-Evaluation Supporting the Observation of a ¹¹C-Methionine PET-Negative Residual Paraskeletal Mass in Multiple Myeloma.

Authors

Seiji Kakiuchi, Chiharu Mishima, Kanae Yamakawa, Naru Tomigaki, Akimasa Sakamoto, Shutaro Fujioka, Isamu Harima, Hiroaki Akiyama, Ryotaro Niwa, Ikumi Takagi, Yoko Kozuki, Yoshiharu Miyata, Nobuko Iwata, Kyoko Yoshihara, Satoshi Yoshihara, Kyoko Otani

Published in

Internal medicine (Tokyo, Japan). Aug 19, 2026. Epub Aug 19, 2026.

Abstract

A 52-year-old man with Bence Jones protein λ-type multiple myeloma developed a large sacral bone-associated, paraskeletal mass. After radiotherapy and idecabtagene vicleucel, serum and urine immunofixation tests were negative, marrow minimal residual disease assessment was negative, and post-treatment ¹¹C-methionine positron emission tomography/computed tomography showed no abnormal uptake in the residual lesion, although computed tomography showed a persistent mass. A re-biopsy was not clinically justified in this case. A re-evaluation of the diagnostic tissue revealed plasma cell-rich areas and acellular collagen-rich stroma with extracellular matrix-associated proteins and λ light chain-derived peptides. Observation was selected, and the mass gradually decreased without any clinical relapse.

PMID:
42618275
Bibliographic data and abstract were imported from PubMed on 20 Aug 2026.

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