Primary omental gastrointestinal stromal tumor (GIST)

Our plain-English summary of Primary omental gastrointestinal stromal tumor (GIST), by T. Todoroki, T. Sano, S. Sakurai, et al (World Journal of Surgical Oncology, 2007).

The study

• Authors: T. Todoroki, T. Sano, S. Sakurai, A. Segawa, T. Saitoh, K. Fujikawa, S. Yamada, N. Hirahara, Y. Tsushima, R. Motojima, T. Motojima
• Journal: World Journal of Surgical Oncology
• Published: 2007;5:66
• Type of article: Case report, Review
• Cited by: 27 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Background: We report herein a rare case of primary omental gastrointestinal stromal tumor (GIST).

Case Presentation: A 65 year-old man was referred to our hospital with a huge abdominal mass occupying the entire left upper abdomen as shown by sonography. On computed tomography (CT), this appeared as a heterogeneous low-density mass with faint enhancement. Abdominal angiography revealed that the right gastroepiploic artery supplied the tumor. With such an indication of gastric GIST, liposarcoma, leiomyosarcoma or mesothelioma laparotomy was performed and revealed that this large mass measured 20 x 17 x 6 cm, arising from the greater omentum. It was completely resected. Histopathologically, it was composed of proliferating spindle and epithelioid cells with an interlacing bundle pattern. Immunohistochemically, the tumor was positive for myeloid stem cell antigen (CD34), weakly positive for c-KIT (CD117) and slightly positive for neuron-specific enolase (NSE), but negative for cytokeratin (CK), alpha-smooth muscle actin (SMA) and S-100 protein. A mutation was identified in the platelet-derived growth factor alpha (PDGFRA) juxtamembrane domain (exon 12, codon561) and the tumor was diagnosed as an omental GIST. The postoperative course was uneventful. The patient is treated by Glevec(R) and is alive well with no sign of relapse.

Conclusion: Our case demonstrated a weak immunohistochemical expression of c-kit (CD117) and a point mutation in PDGFRA exon 12 resulting in an Asp for Val561 substitution. Imatinib therapy as an adjuvant to complete resection has been carried out safely. Because of the rarity of primary omental GISTs, it is inevitable to analyze accumulating data from case reports for a better and more detailed understanding of primary omental GISTs.

In plain English

This case report from a hospital in Ota, Japan, described a 65-year-old man referred in October 2006 with a huge abdominal tumor. Before surgery the doctors suspected liposarcoma, leiomyosarcoma, mesothelioma or a gastric gastrointestinal stromal tumor (GIST). At surgery, a well-encapsulated tumor measuring 20 by 17 by 6 cm was found in the greater omentum and was completely removed. It showed 2 mitotic figures per 50 high power fields and a MIB-1 index of 4.4%. It was weakly or focally positive for CD117 (c-kit) and negative for cytokeratin, alpha-smooth muscle actin and S-100 protein. Sequencing found a point mutation in the PDGFRA gene (exon 12, codon 561), and the tumor was diagnosed as an omental GIST. One risk scheme placed it at intermediate risk, and another rated it high-risk because of its size. The patient took Glevec (imatinib) 300 mg a day and had been disease-free for 6 months. The authors also listed 28 reported omental GIST cases, including this one. They noted that the rarity of these tumors makes their malignant potential hard to assess. The article did not discuss asbestos.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: case report, with a table of previously reported cases from the English-language literature
• Who was studied: one 65-year-old man treated at Motojima General Hospital, Ota, Japan, in October 2006
• Main results:
  • Mesothelioma was among the diagnoses suspected before surgery, along with liposarcoma, leiomyosarcoma and gastric GIST.
  • At laparotomy, a well-encapsulated tumor measuring 20 by 17 by 6 cm was found in the greater omentum.
  • In this patient's tumor, there were 2 mitotic figures per 50 high power fields, and the MIB-1 index was 4.4%.
  • The tumor was weakly or focally positive for CD117 (c-kit) and did not stain for cytokeratin, alpha-smooth muscle actin or S-100 protein.
  • Sequencing showed a point mutation at codon 561 of PDGFRA exon 12, changing Val561 to Asp, and the tumor was diagnosed as an omental GIST.
  • Under the Miettinen and Lasota criteria the tumor fell in group 3b, intermediate risk. Under the Fletcher et al. scheme it was high-risk because of a size above 10 cm.
  • After complete resection, the patient took Glevec 300 mg/day by mouth and had been disease-free for 6 months, with no signs of toxicity reported.
  • The authors counted 28 reported cases of primary omental GIST, including this one. Only half of the collected cases were spindle cell tumors; the rest were epithelioid and myxoid.
• The authors' conclusion: The authors concluded that their case showed weak CD117 expression and a PDGFRA exon 12 point mutation (Asp for Val561). They wrote that imatinib after complete resection had been given safely and may prevent relapse.
• Limitations the authors state:
  • Because primary omental GISTs are rare, the authors said it was difficult to predict this patient's risk of disease progression and malignant potential.
  • Because of rarity (and, the authors also note, the short follow-up), it is difficult to assess malignant potential, treatment efficacy and overall prognosis.

Topics

Medical terms in this study, explained in our Lexicon: Mesothelioma, Laparotomy, Omentum, Epithelioid, STEM, CD34, S-100, Platelet-Derived Growth Factor (PDGF).

Related studies

• Extragastrointestinal Stromal Tumor Presenting as Omental Cyst — A. Monabati, M. Safavi, et al. (2016)
• Expression of neural cell adhesion molecule L1 (CD171) in neuroectodermal and other tumors: An immunohistochemical study of 5155 tumors and critical evaluation of CD171 prognostic value in gastrointestinal stromal tumors — S. Inaguma, Z. Wang, et al. (2016)
• CT-guided core-needle biopsy in omental pathology — F. Pombo, E. Rodriguez, et al. (1997)
• Primary omental mesothelioma: a rare but important differential diagnosis in previous asbestos exposure — A. Harb, E. King, et al. (2010)
• Primary malignant mesothelioma of the greater omentum: report of a case — Y.C. Liu, Y.L. Kuo, et al. (2004)
• Well-Differentiated Papillary Mesothelioma with Omental Calcifications: A Case Report and Review of the Literature — A.S. Erem, S.S. Allamaneni, et al. (2020)

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