Histologic transformation of rectal adenocarcinoma to choriocarcinoma after surgery and chemotherapy: A rare case report and review of the literature.

INTRODUCTION AND IMPORTANCE

Choriocarcinoma is a rapidly progressive, widely metastatic, β-human chorionic gonadotropin (β-hCG)-secreting malignant tumor originating from trophoblast cells. Most choriocarcinomas are pregnancy-related. Choriocarcinoma of nonpregnant origin is very rare.

CASE PRESENTATION

A 60-year-old woman underwent abdominopelvic resection (APR) for low rectal cancer in May 2020. Postoperative pathological findings showed a poorly differentiated adenocarcinoma. Because of a post-operative recurrence, then she underwent chemotherapy for rectal adenocarcinoma. In February 2021, imaging finding showed metastases in her liver, both lungs and pelvis. Surprisingly, the β-hCG level was significantly elevated. A transvaginal pelvic tumor biopsy was performed and the pathology report was presented after discussions: choriocarcinoma differentiated carcinoma was considered, with no adenocarcinoma component detected. Then the patient underwent chemotherapy regimens for choriocarcinoma, which were initially effective but quickly became resistant. The patient died 8 months after the diagnosis of adenocarcinoma of the rectum transformed into choriocarcinoma.

CLINICAL DISCUSSION

The dedifferentiation of adenocarcinoma to choriocarcinoma is rarely diagnosed and the disease is often overlooked, leading to delays in diagnosis and treatment, documenting cases and their clinical outcomes is important for future research and to improve patient prognosis. Perhaps genomic assessment using next-generation sequencing (NGS) technology could help in diagnosis and guide therapeutic strategies.

CONCLUSION

We report a very rare case of non-pregnant choriocarcinoma transformed from primary rectal adenocarcinoma. Awareness of secondary biopsies in special cases and genetic testing based on the dynamics of the disease should be raised in clinical practice to better develop precise treatment plans.