Cheng-Hung Tai, MD, Connie Park, MD, Richa Bhardwaj, MBBS, Ryan Des Jean, MD, Manju Harshan, MD, Nazish Ilyas, MD, Arun Swaminath, MD
Lenox Hill Hospital, New York, NY
Introduction: Colon cancer is the third most common type of cancer globally and approximately 20% patients diagnosed with colon cancer will already have metastatic disease at the time of diagnosis. The liver is the most common site of metastasis, followed by lung, nervous system and bones. Only 15% of patients with stage IV colon cancer will have metastases to locations outside these sites. Here we report a rare presentation of metastatic colon cancer with skeletal muscle (SM) metastases.
Case Description/Methods: 81-year-old male with peripheral artery disease and diabetes mellitus presented with severe right shoulder pain and shortness of breath. Lab work revealed iron deficiency anemia with a hemoglobin of 5.8 g/dl. CT of the chest revealed an 8.2 cm mass in the right lower lung lobe. Positron-emission tomography-CT (PET-CT) revealed increased activity in the right lung, right supraspinatus, gluteus maximus, and right adductor magnus muscles (Figure 1). He then underwent biopsy of the right supraspinatus muscle, which revealed a poorly differentiated metastatic adenocarcinoma with immunohistochemistry (IHC) positive for CK7, and negative for CK 20, CDX-2, TTF-1, NKX3.1 and Napsin A. Colonoscopy revealed a 5 cm friable ulcerated mass in the cecum (Figure 2) with biopsy showing poorly differentiated adenocarcinoma with morphology similar to the muscle mass. Patient subsequently received palliative chemotherapy and underwent a palliative right hemicolectomy. IHC staining of the resected mass was similar to that of the biopsied right supraspinatus muscle (Figure 3). Patient ultimately transitioned to hospice.
Discussion: Muscle metastasis from solid tumors is very rare, accounting for less than 1% of overall metastases. This is in part due to the fact that muscles produce antitumor factors and its sarcolemma or cell membrane acts as a physical barrier against tumor cells. Muscle metastases are more common in primary lung, stomach, or genitourinary tumors and portend poor outcomes due to advanced disease stage. This case appears to be one of the few reported cases of metastatic colon cancer presenting with SM metastases and emphasizes the importance of considering metastatic colon cancer in the differential of SM lesions. It also highlights the importance of PET-CT and IHC in establishing diagnosis and hence guiding appropriate therapy.
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Citation: Cheng-Hung Tai, MD, Connie Park, MD, Richa Bhardwaj, MBBS, Ryan Des Jean, MD, Manju Harshan, MD, Nazish Ilyas, MD, Arun Swaminath, MD. P1112 - SKELETAL MUSCLE (SM) METASTASIS: A RARE INITIAL PRESENTATION OF METASTATIC COLON CANCER. Program No. P1112. ACG 2019 Annual Scientific Meeting Abstracts. San Antonio, Texas: American College of Gastroenterology.