09 March 2025
: Case report 
A 58-Year-Old Man with a History of Autoimmune Thyroiditis Diagnosed with Mucosa-Associated Lymphoid Tissue Lymphoma and Papillary Carcinoma of the Thyroid
Challenging differential diagnosis, Rare disease
Naru Babaya
ABCDEF 1*, Sawa Yoshida ABCD 1, Shinsuke Noso D 1, Yoshihisa Hiromine D 1, Yasunori Taketomo D 1, Takayuki Kimura BD 2, Hiroaki Kakutani BD 3, Takao Satou BD 4, Hiroshi Ikegami DE 1, Norikazu Maeda DE 1
DOI: 10.12659/AJCR.946022
Am J Case Rep 2025; 26:e946022
Figure 4. Photomicrographs of the histopathology of mucosa-assisted lymphoid tissue (MALT) lymphoma of the thyroid gland. (A) Hematoxylin and eosin staining (×400). A substantial portion of normal thyroid architecture appears to be replaced by dense, diffuse infiltrates of small, atypical lymphocytes. (B) Immunohistochemical labeling for IRTA1 (×600). Diffusely proliferated small lymphocytes are IRTA1 positive. (C, D) Immunohistochemical labeling for immunoglobulin light chain, kappa (C), and lambda (D) (×600). The ratio of κ-positive cells to λ-positive cells is more than 10-fold, considered an obvious light chain restriction, and can be judged as monoclonal B-cell proliferation. Scale bar: 50 μm.