Case Report

Giant Gastric Gastrointestinal Stromal Tumour GIST Resistant to Systemic Therapy Imatinib Mesylate with a Rare Sarcomatous Differentiation Subtype: A Case Report and Literature Review

by Saad Alharthi1, Wadha Almohamdi2*, Abdulrahman Alzahrani3, Saga Ali2, Jameel Miro2

1Department of General Surgery, Prince Mansour Military Hospital, Armed Forces Hospital, Taif, Kingdom of Saudi Arabia

2Department of General Surgery, King Faisal Specialist Hospital and Research Centre, Jeddah, Kingdom of Saudi Arabia

3Department of General Surgery, King Fahad Armed Forces Hospital, Jeddah, Kingdom of Saudi Arabia

*Corresponding author: Wadha Almohamdi, Department of General Surgery, King Faisal Specialist Hospital and Research Centre, Jeddah, Kingdom of Saudi Arabia

Received Date: 26 July 2023

Accepted Date: 31 July 2023

Published Date: 02 August 2023

Citation: Alharthi S, Almohamdi W, Alzahrani A, Ali S, Miro J (2023) Giant Gastric Gastrointestinal Stromal Tumour GIST Resistant to Systemic Therapy Imatinib Mesylate with a Rare Sarcomatous Differentiation Subtype: A Case Report and Literature Review. Ann Case Report. 8: 1386. https://doi.org/10.29011/2574-7754.101386

Abstract

Gastrointestinal stromal tumors (GISTs) are rare neoplasms originating from the gastrointestinal tract. We presented a rare case of a young patient with a huge malignant gastric GIST not responding to systemic therapy Imatinib, successfully treated surgically. After complete resection of the malignant GIST, adjuvant therapy with imatinib was initiated. Follow-up CT and endoscopy performed 1 year later confirmed no recurrence of the disease.

Keywords: Gastric Gastrointestinal Stromal Tumours GIST; Giant GIST; Systemic Therapy; Imatinib Mesylate; Case Report

Case presentation

A 62 years old male patient, not known to have any medical illness, heavy smoker, presented to the surgical clinic complaining of upper abdominal pain. The patient was doing well till 1 month prior to his presentation when he started to have vague abdominal pain, mainly upper abdomen. He was tolerating orally well with normal bowel habit. Associated with history of unintentional weight loss of 8 kg in the last month. Performance status ECOG [1]. Upon examination abdomen is slightly distended, soft, there is a mass measures 10*8 cm extending from the left upper quadrant towards the umbilicus, smooth surface, firm in consistency, non-tender, non-pulsating, no skin changes, non-fluctuant, no other palpable masses, no cervical or inguinal lymph nodes. Laboratory tests within normal range. Computated tomography (CT) abdomen was done showed large heterogeneous mass lesion 10.3*19*22.3 cm in diameter (Figure 1). Also, upper endoscopy done as part of the investigations which revealed a large well-demarcated, heterogenous, highly vascular mass lesion noted at the area of body of stomach, fine needle biopsy was taken, biopsy revealed a spindle cell neoplasm, consistent with gastrointestinal stromal tumor (GIST) associated with mild to moderate atypia and rare mitosis (up to 1 mitotic figure), with a background of myxoid changes and necrosis. The tumor cells were positive for DOG-1, CD117(KIT), CD34, and CAM5.2. Negative for S-100 and Desmin. MMR protein test intact protein expression. IHC normal expression of MLH1, MSH2, MSH6 and PMS [2]. The case was discussed in the Gastrointestinal tumor board as patient was presented with large mass with borderline respectable and the decision was to start him on Neoadjuvant Imatinib mesylate with frequent reassessment with imaging to assess the potential of respectability. The main aim of systemic Imatinib is to shrink the tumor for future resection if feasible. Patient was seen by medical oncologist and he started Imatinib for 3 months. Follow up CT showed interval increase in size of previously noted large abdominal mass, currently measuring 16.7*29.6*33.5 in diameter. The lesion became almost cystic with multifocal eccentric enhancing soft tissue density. The lesion displaces the bowel loops anterio-laterally and inseparable from the hepatic lobe, gallbladder and the pancreatic body and tail (Figures 2 and 3). The patient started to have more frequent abdominal pain, developed obstructive symptoms in terms of solid food intolerance with nausea and vomiting, loss of appetite, therefore the decision was made to go for surgical resection. Imatinib was stopped 1 week prior to surgery as per NCCN guidelines. He underwent open partial gastrectomy; intraoperative finding was a huge tumor occupying the whole abdomen. The cystic part was aspirated in order to gain access to the abdomen and around 3 L of blackish fluid was aspirated (Figures 4 and 5). Histopathology revealed GIST, mixed subtype spindle and epithelioid with sarcomatous differentiation. Tumor was unifocal, high grade and 32*17*5 cm in size. Mitotic rate 37/5 mm2. Immunohistochemistry (IHC) Results for MLH1, MSH2, MSH6 and PMS2 were intact nuclear expression. (MMR) Interpretation: No loss of nuclear expression of MMR proteins: No evidence of deficient mismatch repair (low probability of MSI-H). The case was re-discussed in Gastrointestinal tumor board and the decision was to start adjuvant Imatinib. Patient was followed for 1-year post resection. He was doing well, tolerating regular diet, gaining weight with good appetite. Also, follow up CT showed no intra-abdominal or chest metastases.

Figure 1: CT abdomen showed the mass size pre-treatment.

Figure 2: CT abdomen post treatment.