The clinicopathologic significance of psammoma bodies in cytology specimens: A series of 78 cases.

Background: Currently the clinicopathologic significance of psammoma bodies in cytology specimens are not completely understood, including types of cytology specimens and pathologic conditions frequently associated with this unique cytologic feature. In this study, we undertook a retrospective approach to review the specimen types, cytology preparations, patient characteristics, organs or tissues involved and differential diagnoses in cytology specimens with the finding of psammoma bodies.

Methods: Cytology cases with the finding of psammoma bodies from January 2004 to December 2022 were retrieved from our institution's pathology databases, and their clinicopathological features were reviewed.

Results: A total of 78 cytology specimens with the finding of psammoma bodies were recorded in our CoPath system. The mean age at diagnosis was 59 years. The patient group showed female gender predominancy (90%). FNA specimens comprised about 38.5% of total cases. Other common specimen types were body cavity fluids (38.5%), including pleural effusion and peritoneal fluid, and about 20.5% of the cases were pelvic washing performed during gynecologic surgeries. Most cytology cases with psammoma bodies had a malignant diagnosis (69%). About 18% of the cases were in the indeterminate diagnostic categories, with 12% suspicious for malignancy and 6% of the cases with atypical cells. About 5% of cases were placed in the neoplastic category, while 8% of cases were negative for malignancy. About 79% of peritoneal cytology with psammoma bodies were neoplastic and mostly gynecologic tumors. Pleural fluids with psammoma bodies were very likely to be malignant and involved by serous carcinoma (15 of 16 cases, 94%). Papillary thyroid carcinoma was the second most common malignancy in our series, present in about 53% of thyroid cytologies with the finding of psammoma bodies.

Conclusion: Our study showed that psammoma bodies in cytology preparations were more often associated with malignancies in our study of 78 cytology specimens (69%). The most sampled location in our study was peritoneal cavity, followed by pleural cavity, thyroid, lymph nodes, neck masses, and omentum. The clinicopathologic value of psammoma bodies in predicting malignancy varies depending on locations and specimen types.