Metastatic Leiomyosarcoma Presenting as a Pancreatic Mass and Small Bowel Obstruction

Abstract

Leiomyosarcomas are rare smooth muscle cell tumors that primarily originate in the retroperitoneum, genitourinary tract, and gastrointestinal tract. However, among soft-tissue sarcomas, they are a fairly common subtype, accounting for 10-20% of soft-tissue sarcomas. The recurrence rate of leiomyosarcoma is quite high, ranging from 26% to 51%, and dependent upon the origin of the primary lesion. Metastatic tumors are typically detected in the lungs and liver. Metastases to the liver from a primary extremity leiomyosarcoma are rare, and metastases to the pancreas regardless of cancer are very rare in themselves. Here we present the case of a patient with previous history of leiomyosarcoma of the right thigh (Fig. 1), which was treated medically with chemotherapy and radiation, as well as surgical resection. The patient later presented with abdominal pain and elevated amylase and lipase. Computed tomography imaging identified a mass in the head of the pancreas and liver (Fig. 2). Endoscopic ultrasound-guided fine-needle aspiration biopsy of the pancreatic mass demonstrated atypical spindle cell stromal fragments staining positive for the SMMS-1 and actin proteins and negative for desmin. Laparoscopy was performed for staging and biopsy of the liver and confirmed metastatic leiomyosarcoma. While recovering from surgery, the patient developed a closed loop small bowel obstruction (Fig. 3). Urgent surgery discovered a bowel obstruction secondary to intussusception of a metastatic tumor located within the wall of the jejunum. The current plan for the patient's pancreatic and liver lesions is cytotoxic chemotherapy, such as gemcitabine-based therapy, and screening for possible GPC3-CD3 BiTE therapy. This case provides a unique presentation of several rare leiomyosarcoma metastases in a single patient and demonstrates the common recurrence of metastases in these particular types of cancers.2925_A Figure 1. Short TI inversion recovery (STIR) MR image depicting a 4.9 x 1.9 cm mass intra-articular mass within the suprapatellar recess and deep to the medial patellar retinaculum within the right knee.2925_B Figure 2. CT imaging of the abdomen and pelvis with contrast. Arrow demonstrates a 1.7 x 1.3 cm hypodense lesion within the head of the pancreas.2925_C Figure 3. CT imaging of the abdomen and pelvis with contrast. Arrows demonstrate a 1.8 x 1.5 cm enhancing lesion within the small bowel. Bottom images were taken 3 days after top images and demonstrate dilation of the small bowel.