A Rare Case of Medullary Carcinoma of the Ileum

Abstract

Medullary carcinoma of the small intestine is a unique histopathological subtype of colorectal cancers whose underlying mechanism is unknown. The World Health Organization (WHO) recognized this rare condition as a separate entity in colorectal cancers in hopes to better specify treatment. Medullary carcinoma of the colon is a rare neoplasm accounting for less than 0.04% of all colorectal cancers and only 1 case has been reported in the ileum, making the following case report exceptionally rare. A 70 year old male with past medical history of psoriasis, diabetes mellitus, hypertension, and malnutrition presented to the emergency department with diffuse, sharp, abdominal pain of 4 days duration. Physical exam was remarkable only for diffuse tenderness to palpation of abdomen, mild distension, and percutaneous endoscopic gastrostomy tube. Laboratory data showed WBC of 13.4, lipase 18. Colonoscopy perfomed 2 years ago was unremarkable. CT abdomen/pelvis showed intermediate grade small bowel obstruction. Exploratory laparoscopy with ileal mass resection was performed. The necrotic mass measured 4.8x3.9x3.8cm. Specimen pathology showed high-grade medullary carcinoma of the ileum with angiolymphatic invasion. The carcinoma invaded through the muscularis propia into the periileal adipose tissue. The tumoral stage was pT3N0M0. Immunohistochemistry was positive for EMA, and pancytokeratin. Ki-67 index was 80%. CDX-2, CD56 synaptophysin, and chromogranin were negative. The patient was treated with local excision and radiation therapy and instructed on appropriate follow-up. Medullary carcinoma is a rare colorectal neoplasm which typically manifests in the colon, occuring with more frequency in the ascending colon. This neoplasm occurs more frequently in women, and arises in the 7th decade of life. Studies have suggested an association between microsatellite instabilty and the predisposition to developing this neoplasm. Main histopathology consists of intratumor lymphocytic infiltration and poor gland differentiation. Current literature have correlated lack of keratin 20 in medullary neoplasms with variable expression of CDX-2. Treatment modalities aimed at erradication of the neoplasm are yet to be establsihed. It is clear that additional diagnostic and treatment studies need to be conducted, but until then, the treatment for medullary carcinoma of the ileum will remain inconsistent due to a lack of standardized diagnostic criteria.2484_A Figure 1. CT Abdomen and Pelvis demonstrating intermediate grade mid small bowel obstruction.2484_B Figure 2. Sheets of syncytial cells with abundant cytoplasm, and prominent nucleoli.2484_C Figure 3. HE demonstrating tumor invading into muscularis propia.