Papillary carcinomas of thyroid type rarely arise within
struma ovarii. There are limited data on the immunohistochemical and molecular features of these
tumors. Three cases of
papillary carcinoma arising in
struma ovarii (
PCSO) were identified. The clinicopathological features were reviewed and immunohistochemical staining for HBME-1,
cytokeratin (CK) 19, and CD56 was performed.
Tumor DNA was sequenced for somatic mutations using a panel of 26 oncogenes, with a particular focus on BRAF and KRAS mutations. The patients were aged 22, 48, and 55 years. All cases were FIGO stage IA. Two
tumors were of classical histological type, and one was a follicular variant
papillary carcinoma. All
tumors expressed HBME-1 and two were positive for CK19. CD56 was negative in all three cases. One
tumor demonstrated a BRAF G469A mutation in exon 11, and in a second case, a KRAS Q61K double base mutation in exon 3 was detected. These mutations have not been described previously in
PCSO. No mutations were detected in the benign follicular components of the
tumors adjacent to the malignant papillary tissue. None of the patients had
tumor recurrence on clinical follow-up (range 11 months to 8½ years). HBME-1, CK19, and CD56 are useful immunohistochemical markers of
PCSO. Novel BRAF and KRAS mutations were identified in two of three
tumors suggesting that mutations in
PCSO may differ from those commonly identified in
papillary carcinoma of the eutopic thyroid. The clinical significance of these mutations is uncertain but follow-up data in this small series support the generally good prognosis of
PCSO.