# Triple-negative ovarian apocrine carcinoma arising in a giant mature cystic teratoma: Case Report and Case Review

## TL;DR

A rare case of triple-negative ovarian apocrine carcinoma developing in a giant mature cystic teratoma is reported, highlighting the importance of surgical removal and the need for further research.

## Contribution

This is the fifth reported case of apocrine carcinoma arising in a mature cystic teratoma, adding to the limited clinical understanding of this rare tumor transformation.

## Key findings

- The patient had a 35 cm ovarian tumor with histopathological confirmation of high-grade apocrine carcinoma within a mature cystic teratoma.
- Complete surgical excision was achieved with no evidence of recurrence at 6-month follow-up.
- Immunohistochemistry showed AR and EGFR positivity, with no standard systemic therapy established for this rare tumor type.

## Abstract

Mature cystic teratoma (MCT) of the ovary is one of the most common benign ovarian neoplasms in women of reproductive age. Malignant transformation is rare, occurring in approximately 1–2% of cases, and transformation into apocrine carcinoma is exceptionally uncommon. To date, only four such cases have been reported.

We describe a 68-year-old woman with a giant ovarian tumor that had been slowly growing for over 40 years. Imaging revealed a 35 cm cystic mass, consistent with malignant degeneration and serum CA-125 was elevated (559 U/mL). The patient underwent exploratory laparotomy with complete removal of a 11 kg right ovarian tumor. Histopathological examination revealed a mature cystic teratoma of the ovary with malignant transformation into high-grade apocrine carcinoma. The tumor involved the cyst wall multifocally and showed no capsular rupture. Immunohistochemistry showed AR and EGFR positivity, ER and PR negativity, and HER2 score 2+ (FISH negative). The PET-CT showed 2 pericaval lymph nodes possible reactive after surgery. The postoperative course was uneventful, and from the outset the patient refused a comprehensive staging with hysterectomy, omentectomy and lymphadenectomy. At 6-month follow-up, CA-125 remained normal (<8 U/mL), with no evidence of recurrence.

Ovarian apocrine carcinoma arising in MCT is exceedingly rare. Complete surgical excision remains the cornerstone of treatment, as no standard systemic therapy has been established. Further accumulation of similar cases is essential to better understand the biological behavior and optimize management of this rare tumor type.