A Rare Case of Gastric Metastasis in Ewing’s Sarcoma of the Femur

Case Reports in Oncological Medicine
15 May, 2019 ,

This is a case report of Ewing’s sarcoma of the right proximal femur metastasizing to the stomach. A young female treated for Ewing’s sarcoma of the femur in 2012 presented with gastric metastasis after four years of disease-free interval. She was treated with irinotecan-based chemotherapy followed by total gastrectomy with esophagojejunal anastomosis and radiation therapy. In 2016, she had presented with abdominal pain with low-grade fever and unquantified weight loss. Ultrasound abdomen showed epigastric mass measuring. Biopsy from the lesion was reported as malignant round cell tumor, immunopositive for CD99 and FLI-1. 

Source
Full content

A 14-year-old girl presented to our hospital in February 2012 with complaints of painful swelling of the right thigh for 8 months and difficulty in walking. There was no history of trauma, fever, or other constitutional symptoms. Magnetic resonance imaging (MRI) showed right proximal femur lesion. Biopsy from the same was reported as malignant small round cell tumor suggestive of Ewing’s sarcoma. Tumor cells were immunopositive for CD99 and negative for CD3, CD79a, MPO, and desmin. There was no systemic metastasis on further evaluation. She received 6 cycles of chemotherapy with vincristine, ifosfamide, doxorubicin, and etoposide (VIDE) followed by wide local excision of the tumor with endoprosthesis insertion on 06/09/2012. Surgical specimen histopathology examination did not show a viable tumor. Margins were free of tumor. She had received further 8 cycles of vincristine, ifosfamide, and actinomycin D (VAI). She was on regular follow-up. In 2016, she had presented with abdominal pain with low-grade fever and unquantified weight loss. Ultrasound abdomen showed epigastric mass measuring.

Investigation
On computed tomography (CT) of the abdomen and pelvis, an (anteroposterior×craniocaudal×transverse) well-defined exophytic mixed solid-cystic mass was located along the lesser curvature of the stomach bulging into the superior and inferior recesses of the lesser sac. The lesion had thick, irregular walls and enhancing solid components interspersed within. Multiple enhancing intratumoral vessels were present. Mass was seen abutting the inferior surface of the left lobe of the liver superiorly, the pancreatic body posteroinferiorly with no definite invasion. There was no loss of fat plane with adjacent structures. No lymphadenopathy or ascites was noted.
Upper gastrointestinal endoscopy showed a mucosal bulge along the lesser curvature of the body of the stomach and proximal antrum. A single deep mucosal ulcer was noted in the mid-body along the lesser curvature with surrounding mucosal edema and erythema and friability. Clinical differentials considered were a gastrointestinal stromal tumor (GIST), lymphoma, and adenocarcinoma. Metastasis was considered unlikely in view of the stomach is a rare site. However, a biopsy from the lesion was reported as malignant round cell tumor, immunopositive for CD99 and FLI-1. Immunohistochemistry marker for CK, DOG, desmin, and TdT was negative ruling out epithelial tumors, GIST, rhabdomyosarcoma, and lymphoblastic lymphomas, respectively. Bone marrow examination did not reveal metastatic infiltration. No suspicious lesions were seen on bone scintigraphy. CT thorax was negative for lung metastasis.

Treatment
After discussion with the multidisciplinary tumor board (MDT), it was considered to be a metastatic lesion from previous Ewing sarcoma and it was planned to offer her systemic chemotherapy followed by an assessment for gastrectomy. She received 6 cycles of chemotherapy with irinotecan and temozolomide till 07/03/17.
She underwent total gastrectomy with end-to-side esophagojejunal stapled anastomosis and feeding jejunostomy on 07/04/17. At surgery, an exophytic lesion along the lesser curvature of the stomach with mucosal involvement adherent to the transverse mesocolon was found. There was no ascites or liver or nodal metastasis.
Surgical specimen histopathological examination was reported as malignant round cell tumor (viable tumor: 80-85%), consistent with Ewing’s sarcoma. Hematoxylin and eosin staining showed characteristic uniform cells with the round nuclei, small nucleoli with scant-to-moderate clear cytoplasm. Margins were free of tumour. Omentum was noted to have focal tumour deposit. Eight perigastric lymph nodes with reactive hyperplasia. On immunohistochemistry, the tumour cells were diffusely positive for CD99. In view of poor response to chemotherapy, following discussion with the multidisciplinary tumour board, it was decided to rule out anaplastic large-cell lymphoma. The pathologist had a re-look at her biopsy and surgical specimen slides. Lymphoma and GIST IHC panel was negative. FLI-1 was positive on immunohistochemistry. Reverse transcription polymerase chain reaction (RT-PCR) on the gastric resection specimen was negative for EWS-FLI-1 types 1 and 2, EWS-ERG, and EWS-FEV translocations. After ruling out epithelial tumors, rhabdomyosarcoma, lymphoma, and GIST, the likelihood of having an RT-PCR negative Ewing’s sarcoma that is known to have an incidence of 10-15% was considered.
It was decided to offer her radiation therapy in view of poor response to chemotherapy and omental deposit by the MDT team. A renogram was performed prior to the initiation of RT, and informed consent was obtained. She received intensity-modulated radiotherapy to a dose of 50.4 Gy in 28 fractions, delivered once a day over 5 and a half weeks. She received further chemotherapy with irinotecan and temozolomide till July 2017. At the last follow-up in March 2018, the patient was doing well without evidence of the disease.