Fig. 1.

(A) Coronal contrast-enhanced computed tomography image showing a unilocular cyst in the pancreas tail. (B) Six years later, the cyst had grown, with its longest diameter increasing from 2.2 to 3.5 cm, as well as thickening of the cyst wall (arrowheads). (C) The unilocular cyst in the body and tail of the pancreas showing irregular thickening of the cyst wall. (D) Scanning power image showing lymphoid follicles and lymphoplasmacytic infiltration around the cyst wall. (E) The cyst wall was lined mostly by non-mucinous and focally mucinous epithelial cells with mild cytologic atypia. (F) Progesterone receptor nuclear labeling highlighted ovarian-type stromal cells. (G) The irregularly thickened cyst wall contained multiple lymphoid follicles in a background of chronic inflammatory cell infiltrations. (H) Some areas showed dense periductal lymphoplasmacytic infiltrations. (I, J) Several foci of obliterative phlebitis were noted by hematoxylin and eosin staining (I) and elastic staining (J). (K, L) Areas of dense lymphoplasmacytic infiltrations (K) showed numerous IgG4-positive plasma cell infiltrations (L).