S2466 Homomorphic Adenocarcinoma Metastases to the Liver: A Report of Two Cases

Abstract

INTRODUCTION: Classifying a malignant lesion as primary or metastatic can be challenging in some cases. However, identifying the underlying primary disease is crucial for guiding therapy. We describe two cases of liver lesions of unclear etiology that were ultimately determined to be from metastatic adenocarcinoma originating in the ampulla (Case 1) and the colon (Case 2) and were curiously “homomorphic” in appearance. That is, their radiographic appearances resembled a dilated tubular structure akin to the ampulla and a haustrated bowel akin to the colon, respectively. Tumor homomorphism is a relatively new concept utilizing visual similarities to aid in determining an uncertain primary source of metastatic disease. CASE DESCRIPTION/METHODS: Case 1: A 51-year-old male who presented with dyspnea and right upper quadrant abdominal pain underwent computed tomography (CT) of the abdomen, revealing a solitary, 6 cm, cystic lesion in the liver, reminiscent of an ampulla anatomically (Figure 1). Percutaneous biopsy showed adenocarcinoma with signet-ring features of unknown primary. An obstructive mass was seen by endoscopy in the region of the major duodenal papilla. Endoscopic biopsy confirmed tumor cells with signet ring features and a mucinous background (Figure 2). Immunohistochemical evaluation was positive for BerEP4, consistent with signet-ring adenocarcinoma. Case 2: A 46-year-old male presented with five months of generalized abdominal pain, weight loss, constipation, and recent vomiting. CT of the abdomen and pelvis demonstrated numerous hypodense liver lesions. Percutaneous biopsy of the liver lesions revealed malignant glands positive for CK20 and CDX2 and negative for CK7, consistent with intestinal-type adenocarcinoma, suggestive of colorectal primary. On further review of the CT images, annular thickening of the rectosigmoid junction was noted, and the liver lesions were reminiscent of colon, being capacious with haustra-like septations (Figure 3). Colonoscopy revealed a firm, malignant appearing lesion at the rectosigmoid junction. DISCUSSION: The liver is a common site of tumor metastasis. While numerous diagnostic modalities can help detect the primary malignancy, they are often costly, time-consuming, invasive, and may still be inconclusive. Hence, as recently reported in hollow viscous organs and as illustrated here in the context of the liver, the presence of tumor homomorphism may allow clinicians to visually link a metastatic lesion to its primary source, thus providing a unique diagnostic clue.Figure 1.: Computed tomography (CT) scan depicting a 6 cm, ampulla-like, cystic appearing hypodense left hepatic lobe lesion with bile duct and periampullary thickening resulting in mass effect and consequent duodenal stenosis.Figure 2.: Ancillary studies on cytology specimen illustrating malignant cells with signet ring features.Figure 3.: Computed tomography (CT) scan of the abdomen and pelvis illustrating liver metastasis reminiscent of a sigmoid colon anatomically delineating the concept of homomorphism.