Abstract
Objective : We examined the findings and significance of mountain range-like clusters (MRLCs) in Papanicolaou-stained thyroid fine needle aspiration (TFNA) biopsy specimens.
Study Design : We studied 64 cases of MALT lymphoma (n=44) or Hashimoto’s thyroiditis (HT ; n=20) that were diagnosed by histological and cytological examinations at Kuma hospital. To prepare the smear samples, each of the glass slide onto which the aspirates were plated was sandwiched with another slide, and the smears were prepared by vertically separating the two slides.
We examined the nuclear findings of the neoplastic cells, the cellular clusters derived from the MALT lymphomas, and the origin of the MRLCs. The findings for distinguishing MALT lymphoma from HT were assessed by discriminant analysis. MRLCs were defined as long and consecutive cellular clusters in the low-power fields of Papanicolaou-stained specimens with a cluster length÷mean cluster width of>4.
Results : When the cutoff value for the frequency of [ISN-PN] (irregularly-shaped nucleus with prominent nucleolus) of 20% was used in combination with the presence of LEL-MALTs (cellular clusters derived from lymphoepithelial lesions) and MRLCs, the accuracy rate for distinguishing MALT lymphoma from HT was 97%. MRLCs were observed in 90% of the MALT lymphomas, but in none of the cases of HT. Follicular dendritic cell-like cells, tingible-body macrophages, small lymphocytes, and neoplastic cells were intermingled with the MRLCs.
Conclusion : Our findings suggest that MRLCs are derived from regions of follicular colonization in MALT lymphomas, and that the presence of MRLCs is one of the useful findings for differentiating MALT lymphoma from HT.
