Arias-Stella atypia in a paratubal cyst: a rare phenomenon with potential diagnostic pitfalls.

Background: Arias-Stella reaction is commonly encountered in the endometrium during the gestational period and puerperium. Similar changes in the tubal epithelium are exceedingly rare. The cytologic findings of this phenomenon have never been described before.

Methods: Cytologic findings of Arias-Stella changes in the lining cells of a left paratubal cyst in a 41-year-old woman were examined. The smears showed occasional small clusters or isolated tubal epithelial cells consisting of a mixture of ciliated and secretory cells. Some of the ciliated cells showed a marked increase in nuclear and cytoplasmic volume and possessed coarse chromatin, prominent, angulated nucleoli, dense, amphophilic cytoplasm; and a discrete cell membrane. The nuclear membrane was still thin and regular, and these cells were mitotically inactive. The preservation of apical cilia in some of them ensured their benign nature. In some areas, clusters of secretory cells with an increase in both nuclear and cytoplasmic volume and ample, clear cytoplasm were also found. There were small, monolayered sheets of regular and benign-looking epithelial cells with a honeycomb arrangement, suggesting that the Arias-Stella atypia was focal.

Conclusions: In view of the presence of scattered giant cells with coarse chromatin and angulated macronucleoli, a false positive cytologic diagnosis of malignancy can be made if one does not pay attention to the coexistence of apical cilia and other subtle changes, including the usual nuclear/cytoplasmic ratio, thin and regular nuclear membrane and absence of mitotic activity.