Pathological transformation of rectal adenocarcinoma to choriocarcinoma in a male patient: A case report and review of the literature.

Choriocarcinoma associated with poorly differentiated somatic cell carcinoma is a rare disease and there are limitations in its clinical management. The present study describes the case of a 62-year-old male patient with rectal adenocarcinoma; after undergoing three lines of standard colorectal cancer treatment, the rectal adenocarcinoma exhibited abnormal differentiation into choriocarcinoma with a notable increase in serum β-human chorionic gonadotropin (β-hCG). The patient underwent two cycles of EMP/CO chemotherapy (etoposide, methotrexate, cisplatin/cyclophosphamide and vincristine); the standard treatment regimen for choriocarcinoma is EMA/CO (etoposide, methotrexate, actinomycin D/cyclophosphamide and vincristine), whereas in the present case, cisplatin was used in place of actinomycin D. Subsequently, β-hCG levels exhibited a marked decrease. After the first cycle of chemotherapy, the β-hCG level decreased from >15,000 mIU/ml to 4,109 mIU/ml. Notably, the second cycle of chemotherapy was delayed due to fever and perianal abscess, after which the β-hCG level rose again to >15,000 mIU/ml; yet, after chemotherapy on days 1-2 of the second cycle, the β-hCG level decreased again to 11,900 mIU/ml. However, due to poor tolerance and rapid disease progression, the patient was unable to continue receiving treatment and ultimately died. Given the rarity and clinical intractability of this disease, the relevant literature was reviewed to offer insights into its mechanism, diagnosis and treatment. The current case report illustrates the pathological transformation from rectal adenocarcinoma to choriocarcinoma in a male patient, which provides evidence for the abnormal differentiation of somatic cell carcinoma into choriocarcinoma. Concurrently, post-treatment β-hCG level changes validated the therapeutic efficacy of EMP/CO. Furthermore, given the promising advances in antiangiogenic and immunotherapy research, these therapeutic approaches warrant further exploration alongside chemotherapy.