Abstract
Objectives : We examined the characteristic cytological features of MALT lymphoma with extreme plasma cell (PC) differentiation (MALT-EPCD) in Papanicolaou-stained thyroid fine needle aspiration cytology (TFNA) specimens.
Study Design : We studied the findings in TFNA specimens obtained from 27 cases of thyroid disease, including 7 cases of MALT-EPCD and 20 cases of Hashimoto’s thyroiditis (HT) that were diagnosed by histological and cytological examinations at Kuma Hospital.
We examined the percentages of PCs and of cells containing irregularly-shaped nuclei with prominent nucleoli (ISN-PN cells), the percent [sum of PCs plus ISN-PN cells], and the percentages of mountain range-like clusters (MRLCs) and LEL-like clusters (LELCs).
Results : MALT-EPCD : The findings were as follows : percentage of PCs, 24.0% (15-34%) ; percentage of ISN-PN cells, 9.3% (5-14%) ; percentage of MRLCs, 28.6% ; percentage of LELCs, 42.9%.
HT : Percentage of PCs, 2.6% (0-18%) ; percentage of ISN-PN cells, 10.1% (0-25%) ; MRLCs and LELCs were absent.
The mean percent [sum of PCs plus ISN-PN cells] was 33% (29-39%) in MALT-EPCD, 29% in the case of MALT-EPCD with the lowest percentage of PCs (PC : 15%) and 18% in the case of HT with the highest percentage of PCs (PC : 18%).
Conclusion : To differentiate MALT-EPCD from HT, it would be useful to examine #1) the percentage of PCs, #2) the percentage of ISN-PN cells and #3) the sum of #1 plus #2. Percentage of PCs of ≧15%, and percent [sum of PCs plus ISN-PN cells] of ≧30% were regarded as findings characteristic of MALT-EPCD. In addition, the detection of MRLCs or LELCs in MALT-EPCD, even at a low rate, could be helpful for differentiating MALT-EPCD from HT.
