Medullary carcinoma of the large intestine: A population based analysis

Abstract

Abstract. Medullary carcinoma (MC) of the colorectum is a relatively new histological type of adenocarcinoma characterized by poor glandular differentiation and intraepithelial lymphocytic infiltrate. To date, there has been no epidemiological study of this rare tumor type, which has now been incorporated as a separate entity in the World Health Organization (WHO) classification of colorectal cancers. We used the population-based registries of the Surveillance, Epidemiology and End Results (SEER) database to identify all cases of colorectal MC between 1973 and 2006 and compared them to poorly and undifferentiated colonic adenocarcinomas (PDA and UDA, respectively). We observed that MCs were rare tumors, constituting approximately 5-8 cases for every 10,000 colon cancers diagnosed, with a mean annual incidence of 3.47 (±0.75) per 10 million population. Mean age at diagnosis was 69.3 (±12.5) years, with incidence increasing with age. MCs were twice as common in females, who presented at a later age, with a lower stage and a trend towards favorable prognosis. MCs were extremely rare among AfricanAmericans. MCs were most common in the proximal colon (74%), where they present at a later age than the sigmoid colon. There were no cases reliably identified in the rectum or appendix. Serum carcinoembryonic antigen levels (CEA) were elevated prior to first course of treatment in 40% of the patients. MCs were more commonly poorly differentiated (72%), with 22% being undifferentiated. MCs commonly presented with Stage II disease, with 10% presenting with metastases. Only one patient presented with N2b disease (>7 positive nodes). Early outcome analyses showed that MCs have 1-and 2-year relative survival rates of 92.7 and 73.8% respectively. Although MCs showed a trend towards better early overall survival, undifferentiated MCs present more commonly with Stage III, with comparatively worse early outcomes.

Microsatellite Instability in Medullary Carcinoma of the Colon

“…These tumors are usually larger in size and have a poorly differentiated or undifferentiated histological appearance. 3 …”

“…Medullary carcinoma tipically present a lesser rate of nodal metastasis and a minor tendency toward extramural and invasion, when compared to poorly differentiated adenocarcinoma, 4 , 7 while the linfovascular invasion con be relatively high (62.9 vs 36.5%). 7 In comparison with undifferentiated and poorly-differentiated adenocarcinomas of the large intestine, MC has a better prognosis 3 and it improves further in case of MSI - H. 8 …”

“…Essentially, MCs are a solid variety of adenocarcinoma with very little glandular differentiation; for this reason they are morphologically similar to poorly differentiated adenocarcinoma and undifferentiated adenocarcinoma and histological differential diagnosis can be extremely challenging. 1 MC can be represented by a morphological type of minimally differentiated adenocarcinoma (0.03%), poorly differentiated (72%), and undifferentiated (22%); 2 , 3 these tumors are typically more common in older females and tend to have a distinct clinical behavior with less nodal involvement and a better prognosis. 4 MC tend to be right-sided (54%) and incidence increase directly with the age (mean age at diagnosis 69.3 years); they are usually diagnosed at an advanced stage but distant metastases are rare at presentation (10%).…”

Prognostic stratification of colorectal cancer patients: current perspectives

“…5 Medullary carcinomas arise frequently in the proximal colon, with an incidence increasing with age and a female predominance. 22 , 23 …”

“…Medullary differentiation is an indicator of favorable prognosis: follow-up data showed 1- and 2- year survival rates of 92.7% and 73.8%, respectively. 23 On the molecular level, the majority of medullary carcinomas are MSI-H cancers. 24 …”