Rare histologic types of rectal cancer: A monocentric cases series report

Primary Rectal Tumor With Extensive Choriocarcinoma Differentiation in a Woman With Lung, Liver and Disseminated Peritoneal Disease: A Primary Rectal Adenocarcinoma With Extensive Choriocarcinoma Differentiation or Primary Rectal Choriocarcinoma?

Primary rectal adenocarcinoma with extensive choriocarcinomatous differentiation is a rare neoplasm, with only sporadic cases reported worldwide. The prognosis is typically poor, and no standard therapy has been established for this tumor. We report a case of a 63-year-old woman who presented with lower abdominal and pelvic discomfort, as well as rectal bleeding. Endoscopy revealed a rectal tumor. She was diagnosed with primary rectal adenocarcinoma with extensive choriocarcinomatous differentiation, accompanied by liver metastasis and peritoneal carcinomatosis. The immunohistochemical profile demonstrated strong and diffuse positivity for keratin (AE1/AE3), beta-human chorionic gonadotropin (β-HCG), p53, MYC, p16, and Ki-67. Molecular analysis indicated mutations in KRAS, TP53, and PI3KCA. Despite the tumor's profile, the serum β-HCG level was not elevated. A chemotherapy regimen for metastatic colorectal adenocarcinoma was initiated, but there was a poor response, with rapid tumor progression. The patient survived for only 5 months postdiagnosis. We discuss the histopathological, immunohistochemical, and molecular findings, emphasizing their relevance to the differential diagnosis of neoplasms with choriocarcinomatous differentiation.

Signet ring cell carcinoma of the rectum: atypical metastatic presentation

Colorectal cancer is the third most common cancer in the world and the fourth most common cause of death related to cancer. Signet ring cell carcinoma represents an uncommon histological type for rectal cancer with less than 1% of all rectal neoplasms. It usually behaves aggressively and has an inferior prognosis. We present the case of a young man diagnosed with signet ring cell rectal carcinoma. He underwent neoadjuvant therapy with partial response, had surgery with curative intent and showed local recurrence after only 3 months. Disease progression happened only weeks after recurrence with metastasis to vertebrae, extraocular muscles, bone marrow and skin. He is currently receiving palliative chemotherapy.