# Malignant transformations in mature cystic teratomas: A case report and literature review

## TL;DR

This paper reports a rare case of a testicular teratoma turning into mucinous adenocarcinoma and highlights the importance of early detection and multidisciplinary treatment.

## Contribution

The study presents a unique case of malignant transformation in a testicular teratoma and emphasizes the need for timely documentation of such rare events.

## Key findings

- Testicular teratomas can rarely transform into mucinous adenocarcinoma.
- Immunohistochemical markers like CDX2, CK20, and CK7 are crucial for diagnosis.
- Early detection and multidisciplinary management improve prognosis in these rare cases.

## Abstract

Testicular teratomas, although generally benign, may rarely undergo malignant transformation into somatic cancers, most notably, adenocarcinomas. The incidence of malignancy transformation in ovarian teratomas is well-established at ~2%; however, it is extremely uncommon for testicular and extragonadal teratomas to undergo such transformations. The present study describes a unique case of a testicular teratoma that underwent malignant transformation into mucinous adenocarcinoma. The pathophysiology underlying testicular teratoma transformation remains incompletely understood, with several mechanisms proposed, including the malignancy of totipotent embryonal carcinoma cells or the malignant differentiation of mature teratomatous elements. Additionally, secondary malignancy, often induced by chemotherapy or radiotherapy, is also a contributing factor in certain cases. Immunohistochemical analyses play a crucial role in diagnosing these rare malignancies, with markers such as CDX2, CK20 and CK7 helping to differentiate the adenocarcinoma phenotypes. Despite the rarity of such cases, it is imperative to recognize the potential for aggressive progression, particularly when adenocarcinoma is involved, as these cases require intensive management, including chemotherapy and, sometimes, surgical intervention. The present study emphasizes how crucial early discovery is for improving prognosis and treatment results for individuals with malignant transformation of testicular teratomas, as well as the value of a multidisciplinary approach. Given the limited number of reported cases and lack of standardized management guidelines, the timely documentation and analysis of such rare presentations are essential to guide future clinical decision-making.