Metastatic mucinous colorectal adenocarcinoma

Discussion:

This is a very dramatic presentation of metastatic mucinous adenocarcinoma of the colon. The primary tumor involves a long segment of the sigmoid colon and invades into the bladder with a large intraluminal mass. There are small but abnormal lymph nodes within the pericolonic mesentery and a larger nodal metastasis in the left common iliac chain. 

Finally, there are several liver lesions which are classic for mucinous colorectal carcinoma metastasis: intermediate/mucin attenuation with small, stippled calcifications. As noted in the discussion, there are also several benign hepatic cysts. This serves as a great internal comparison for the two types of lesions. In general, calcifications in multiple hepatic lesions is highly suspicious for mucinous adenocarcinoma metastases (colon, ovary, pancreas).  Mucinous adenocarcinoma is considered poorly differentiated and frequently presents at a more advanced stage than non-mucinous subtypes, likely due to a "less firm" consistency causing symptoms later than non-mucinous adenocarcinoma. 

This patient underwent sigmoidoscopic biopsy of the primary mass. However, the biopsy returned non-diagnostic, as no cells were present. This is a common pitfall for biopsy: there is a paucity of cellular material due to abundant mucin production, making the biopsy yield frequently low. However, given the appearance of the primary tumor and classic appearance of the liver metastases, the diagnosis is basically certain. Due to the patient's advanced age, comorbidities, and advanced disease, she elected no further work-up or treatment. 

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