Background: Ovarian cancer is the sixth most common cancer among women in Croatia. The most frequent type is epithelial, which accounts for about 90% of all ovarian cancers. The challenge with this type of ovarian cancer lies with diagnosis and subsequent high mortality, with approximately 90% of all serous ovarian cancers diagnosed in the FIGO III-IV stage, and rarely in FIGO I. Diagnosis is additionally complicated by morphologic heterogeneity, probably relating to transformation or progression from different tumor subtypes. Case: A 53-year-old woman, postmenopausal for 3.5 years, was found to have a right ovarian solid and cystic formation measuring 53 mm in diameter on routine transvaginal ultrasound and which had been followed for more than 5 years and described as benign and asymptomatic. Hysterectomy and bilateral adnexectomy were performed, and staging was described as FIGO IA. This case shows squamous metaplasia in the marginal part of the depicted sample, which has led to squamous differentiation in serous papillary cystadenocarcinoma. Immunohistochemical staining for WT-1, p53, and p63 was performed, and it proved to be focal positive for WT1 or diffusely positive for p53 and p63. Conclusion: This was a very rare case of multicystic papillary adenocarcinoma with marginal squamous differentiation. The mechanisms of metaplasia in similar cases remain unknown, and the possible effects of minor components on prognosis should be investigated intensively. © Science Printers and Publishers, Inc.