Medullary Carcinoma of the Colon: A Rare Histopathological Subtype of Colorectal Cancer
Year: 2026
Type: article
Study design: Case Report
Abstract: Medullary colon carcinoma (MCC) is an uncommon histological subtype, accounting for approximately 0.03% of all cases of colorectal cancer (CCR). It predominantly affects older white female individuals, is typically right-sided, exhibits poorly-differentiated histology, and shows a strong association with microsatellite instability (MSI). We herein report a case of MCC, with the diagnosis confirmed by an immunohistochemistry panel. An 81-year-old woman presented with abdominal pain, loss of weight, and severe anemia persisting for 6 months. A physical examination revealed a palpable, mobile mass in the right flank and iliac fossa. Colonoscopy identified a large, vegetative, stenosing tumor in the right colon. Computed tomography confirmed the presence of the ascending colon mass and enlarged regional lymph nodes, without evidence of hepatic or pulmonary metastases. She underwent an elective extended right colectomy with third-tier (D3) lymphadenectomy. A histopathological analysis revealed a poorly-differentiated adenocarcinoma infiltrating the colonic wall up to the subserosa, with metastasis to 3 out of 33 resected lymph nodes (T3N1b). Immunohistochemical staining was positive for caudal-type homeobox 2 (CDX2), special AT-rich sequence-binding protein 2 (SATB2), and cytokeratin (AE1/AE3), with complete loss of MutL Homolog 1 (MLH1) expression, consistent with the diagnosis of MCC. Postoperatively, the patient received 9 cycles of adjuvant chemotherapy with 5-fluorouracil (5-FU) and oxaliplatin. She remains asymptomatic and free of disease recurrence at 1 year of follow-up. A rare and distinct histological subtype of CRC, the diagnosis of MCC often relies on immunohistochemical evaluation, particularly demonstrating MSI. Due to its rarity and unique pathological features, awareness and accurate identification of MCC are essential for the appropriate management and prognostic assessment.
Source: Journal of Coloproctology
Institution: Universidade de São Paulo
Language: English
Subfield: Pathology and Forensic Medicine
Field: Medicine
Domain: Health Sciences
Open Access status: diamond
OpenAlex ID: W7223373744