Intraoperative Assessment of Metastatic Thyroid Cancer to Brain Using Combined Frozen Section, Squash (Crush), and Touch Preparation Cytology at the Queens Medical Center: A 30-Year Retrospective Analysis

Objective: Thyroid cancer with brain metastasis is extremely rare (incidence 0.15-2.1%), leading to infrequent pathologic experience. We aimed to determine their incidence and to assess efficacy of their intraoperative detection.

Method: Brain lesions assessed intraoperatively from 1/1/96-12/31/25 were sought.

Results: Of 1210 brain lesions, 1079 (89.2%) and 131 (10.8%) were neoplastic and non-neoplastic, respectively. There were only 2 (1%) metastatic thyroid cancers. The 1st patient was a 59 year old female with papillary thyroid carcinoma (PTC) with BRAF V600E and AKT1 mutations diagnosed 5 years previously, who presented with right temporal brain metastasis and malignant pleural effusion 3 months later. The 2nd patient was a 73 year old female with dural metastasis from PTC with BRAF V600E, TERT, and ATM mutations diagnosed 1 year previously, with intervening right upper lobe and left acetabulum involvement. Intraoperative assessment for these metastatic thyroid cancers correlated with their final diagnoses.

Conclusion: Thyroid cancers comprised 1% of metastases and 0.16% of all brain lesions encountered at our institution. Combined squash/touch preps and frozen section examination proved accurate in the intraoperative assessment of this rare entity.