Clinicopathologic study of succinate-dehydrogenase-deficient gastrointestinal stromal tumors: A single-institutional experience in China

SDHA Germline Mutations in SDH-Deficient GISTs: A Current Update

Loss of function of the succinate dehydrogenase complex characterizes 20–40% of all KIT/PDGFRA-negative GIST. Approximately half of SDH-deficient GIST patients lack SDHx mutations and are caused by a hypermethylation of the SDHC promoter, which causes the repression of SDHC transcription and depletion of SDHC protein levels through a mechanism described as epimutation. The remaining 50% of SDH-deficient GISTs have mutations in one of the SDH subunits and SDHA mutations are the most common (30%), with consequent loss of SDHA and SDHB protein expression immunohistochemically. SDHB, SDHC, and SDHD mutations in GIST occur in only 20–30% of cases and most of these SDH mutations are germline. More recently, germline mutations in SDHA have also been described in several patients with loss of function of the SDH complex. SDHA-mutant patients usually carry two mutational events at the SDHA locus, either the loss of the wild type allele or a second somatic event in compound heterozygosis. This review provides an overview of all data in the literature regarding SDHA-mutated GIST, especially focusing on the prevalence of germline mutations in SDH-deficient GIST populations who harbor SDHA somatic mutations, and offers a view towards understanding the importance of genetic counselling for SDHA-variant carriers and relatives.

Molecular Mechanisms of Gastrointestinal Stromal Tumors and Their Impact on Systemic Therapy Decision

Gastrointestinal stromal tumors (GISTs) are soft tissue sarcomas that mostly derive from Cajal cell precursors. They are by far the most common soft tissue sarcomas. Clinically, they present as gastrointestinal malignancies, most often with bleeding, pain, or intestinal obstruction. They are identified using characteristic immunohistochemical staining for CD117 and DOG1. Improved understanding of the molecular biology of these tumors and identification of oncogenic drivers have altered the systemic treatment of primarily disseminated disease, which is becoming increasingly complex. Gain-of-function mutations in KIT or PDGFRA genes represent the driving mutations in more than 90% of all GISTs. These patients exhibit good responses to targeted therapy with tyrosine kinase inhibitors (TKIs). Gastrointestinal stromal tumors lacking the KIT/PDGFRA mutations, however, represent distinct clinico-pathological entities with diverse molecular mechanisms of oncogenesis. In these patients, therapy with TKIs is hardly ever as effective as for KIT/PDGFRA-mutated GISTs. This review provides an outline of current diagnostics aimed at identifying clinically relevant driver alterations and a comprehensive summary of current treatments with targeted therapies for patients with GISTs in both adjuvant and metastatic settings. The role of molecular testing and the selection of the optimal targeted therapy according to the identified oncogenic driver are reviewed and some future directions are proposed.

NCCN Guidelines® Insights: Gastrointestinal Stromal Tumors, Version 2.2022

Gastrointestinal stromal tumors (GIST) are the most common type of soft tissue sarcoma that occur throughout the gastrointestinal tract. Most of these tumors are caused by oncogenic activating mutations in the KIT or PDGFRA genes. The NCCN Guidelines for GIST provide recommendations for the diagnosis, evaluation, treatment, and follow-up of patients with these tumors. These NCCN Guidelines Insights summarize the panel discussion behind recent important updates to the guidelines, including revised systemic therapy options for unresectable, progressive, or metastatic GIST based on mutational status, and updated recommendations for the management of GIST that develop resistance to specific tyrosine kinase inhibitors.

Targeted therapy in SDH-deficient GIST

The medical management of advanced gastrointestinal stromal tumors (GIST) has improved with the development of tyrosine kinase inhibitors (TKIs) targeting KIT and PDGFRA mutations. However, approximately 5-10% of GIST lack KIT and PDGFRA mutations, and about a half are deficient in succinate dehydrogenase (SDH) that promotes carcinogenesis by the cytoplasmic accumulation of succinate. This rare group of GIST primarily occurs in the younger patients than other subtypes, and is frequently associated with hereditary syndromes. The role of TKIs in patients with SDH-deficient GIST is controversial, with conflicting results; thus, there is an urgent need to uncover the disease mechanisms, treatment patterns, and responses to systemic therapy among these patients. Here, based on an extensive literature search, we have provided a rigorous overview of the current evidence on the medical treatment of SDH-deficient GIST.

Succinate dehydrogenase deficient gastrointestinal stromal tumor in a three month old boy with a fatal clinical course: a case report and review of literature

Background

Succinate dehydrogenase deficient gastrointestinal stromal tumors (SDH-deficient GISTs), which lack KIT or PDGFRA mutations demonstrate unique clinical and pathological features, and they respond poorly to standard targeted therapy. We herein present a novel case of SDH-deficient GIST in a three-month-old infant’s colon mesentery, and he is the youngest patientto date.

Case presentation

The infantpresented with complaints of blood in the stool. CT showed a 6.3 × 4.6 cm mass in the left lower retroperitoneal. Complete resection of tumor and segmental bowel resection was performed without regional lymphadenectomy. Histologically, tumor cells were distinctive in their multinodular colon wall involvement with interspersed tracts of colon wall smooth muscle. The tumor was composed mainly of epithelioid cells. Immunohistochemically, the tumor cells were positive for Vim, CD117, PDGFR, while negative for SDHB. Mutational analysis showed a synonymous mutation for SDHB and wild-type for KIT and PDGFRA. Two months after surgery, metastases were found and Imatinib was administered. Unfortunately, the disease continued to progress, and the infant died 5 months after surgery.

Conclusions

SDH-deficient GISTs comprise a subgroup of a relatively rare tumor type and show a number of clinically and biologically unique features, especially for infants. It is of great importance to developing new therapeutic targets and novel specific drugs.

Succinate dehydrogenase-deficient gastrointestinal stromal tumor of stomach diagnosed by endoscopic ultrasound-guided fine-needle biopsy: Report of a distinct subtype in cytology

Succinate dehydrogenase (SDH)-deficient gastrointestinal stromal tumors (GISTs) are characterized by the lack of mutations in KIT receptor tyrosine kinase complex and platelet derived growth factor receptor-alpha (PDGFRA) that are commonly found in the majority of GISTs. SDH-deficient GISTs comprise approximately 5%-10% of all GISTs. This subset may be associated with Carney Triad and Carney-Stratakis syndrome. SDH-deficient GISTs show unique demographic, radiologic, morphologic findings, clinical behavior, and treatment response. To our knowledge, the identification and characterization of this subset of GISTs have not yet been described in the cytopathology literature. By understanding the clinical as well as the other unique features of this tumor, in addition to the rapidly evolving identification of specific molecular alterations and targeted therapies, cytopathologists may play an important role in the diagnosis and work-up of these patients to allow clinicians to better manage and treat them. We present a young female with gastric SDH-deficient GIST diagnosed by fine-needle biopsy with supporting surgical pathology follow-up and molecular confirmation. This report suggests that the diagnosis of SDH-deficient GIST can be made on cytology in the appropriate clinical setting by using cytomorphologic features and demonstrating SDH loss by IHC on the cell block. In addition, molecular testing may be possible on the cytology cell block or supernatant to confirm the diagnosis.

Primary Gastrointestinal Stromal Tumor Mimicking as Gynecologic Mass: Characteristics, Management, and Prognosis

BACKGROUND

Primary gastrointestinal stromal tumor (GIST)-mimicking gynecologic masses are easily misdiagnosed. This study aimed to investigate the clinicopathological features, management, and prognosis of primary GIST mimicking as gynecologic mass.

METHODS

Clinicopathological and survival data of GIST mimicking as gynecologic mass admitted to our center from January 2005 to December 2017 were retrospectively analyzed.

RESULTS

Thirty-eight patients were included. The most common primary tumor site was the jejunoileum (n = 33, 86.9%), and 33 patients (86.9%) were classified as high recurrence risk. The short-term outcomes of operative incision length (P = 0.004), time to gas passage (P = 0.002), and hospital stay (P = 0.012) with laparoscopy-assisted resection were significantly shorter than those with open resection, showing no significant differences of long-term outcomes. With a median follow-up of 56 mo for 31 patients (81.6%), 18 (58.1%) received adjuvant therapy with imatinib. The 5-year disease-free survival and disease-specific survival of pelvic high-risk GIST was 37.0% and 48.3%, respectively; both were significantly lower than those of the other female high-risk group (both P < 0.05).

CONCLUSIONS

GIST mimicking as gynecologic mass is not uncommon, most originate from the jejunoileum and have a high risk of recurrence. Laparoscopy-assisted resection may be preferable for more favorable short-term outcomes. Compared with the other female high-risk GIST, pelvic high-risk GIST has a significantly worse prognosis; a longer duration of adjuvant therapy with imatinib than recommended may be beneficial.

[Imatinib and beyond-what is important for surgery?]

The treatment of gastrointestinal stromal tumors (GIST) has dramatically improved since the introduction of small molecule KIT proto-oncogene receptor tyrosine kinase inhibitors. Nevertheless, the cure of patients is still based on surgical treatment of the primary tumor. The chance of long-term tumor control by tyrosine kinase inhibitors (TKI) even in the metastatic setting also appears to be improved after achieving a surgical complete resection. The decision on which patients will most likely profit from multimodal treatment approaches is increasingly based on complex molecular predictors in addition to clinical factors and also a profound understanding of the biology of GIST that requires discussion in a multidisciplinary, highly experienced treatment team. Novel, more potent inhibitors enable a response to treatment in so far treatment-refractory GIST subtypes, such as the platelet-derived growth factor receptor (PDGFR) D842V mutated GIST subtype and also appear to show treatment benefits even in KIT mutated GIST after the failure of all approved treatments. These treatments are expected to profoundly change treatment algorithms in the near future.

Succinate Dehydrogenase–Deficient Gastrointestinal Stromal Tumors

Succinate dehydrogenase (SDH)–deficient gastrointestinal stromal tumor (GIST) is a subset of wild-type GIST that constitutes approximately 10% of gastric GISTs. SDH-mutated GISTs lack mutations in the proto-oncogene receptor tyrosine kinase (also known as KIT, c-KIT, or CD117) or platelet-derived growth factor receptor α (PDGFR-α). These tumors have female predilection, affect children and young adults, and have a spectrum of behavior from indolent to progressive. These tumors have characteristic morphologic features including multinodular architecture, multiple tumors, lymphovascular involvement, and occasional lymph node metastasis. They can be seen in patients with Carney triad or Carney-Stratakis syndrome. Although a mutation in any one of the SDH subunits can be pathogenic, deficiency of a single subunit leads to loss of detectable SDH subunit B by immunohistochemistry, enabling a convenient, tissue-based screening method. The prognosis and the clinical course of these tumors is different from that of KIT- or PDGFR-α–mutated GISTs. Surgical management is considered the main line of treatment. SDH-mutated GISTs do not respond well to the common targeted therapy, with no objective tumor response to imatinib. The role of the pathologist in diagnosing these cases is imperative in management and subsequent follow-up.

Predictors of lymph node metastasis in patients with gastrointestinal stromal tumors (GISTs)

BACKGROUND

Lymph node metastasis is not common among patients with gastrointestinal stromal tumors (GISTs) and its prognostic value is controversial. The purposes of this study are to identify predictors of lymph node metastasis and determine its prognostic associations.

METHODS

A retrospective analysis of the surveillance, epidemiology and end results (SEER) database was performed. Patients with GISTs that underwent surgery and pathologic nodal staging were identified. Logistic regression and Cox regression were performed to identify independent predictors and prognostic factors, respectively.

RESULTS

Of 1430 patients (age: 61.5 ± 14.5 years, 52% males), 140 (9.8%) had lymph node metastasis. On multivariable analysis, distant metastasis was the only independent predictor of lymph node metastasis (OR 4.95, 95% CI: 2.43-10.08, p < 0.001). In the entire cohort, lymph node metastasis did not reflect a worse overall survival (OS, HR 1.12, 95% CI: 0.49-2.58, p = 0.794) or disease-specific survival (DSS, HR 0.95, 95% CI: 0.31-2.88, p = 0.924), but was an independent predictor of worse OS in 51 patients (25.4% of 201 patients) who presented with both lymph node metastasis and synchronous distant metastasis (HR 2, 95% CI: 1.25-3.21, p = 0.004). Lymph node metastasis was also independently associated with worse survival among patients with small intestinal (OS: HR 1.88, 95% CI: 1.15-3.1, p = 0.013) and colorectal tumors (OS: HR 3.41, 95% CI: 1.56-7.46, p = 0.002, DSS: HR 3.58, 95% CI: 1.27-10.06, p = 0.016).

CONCLUSIONS

Metastatic disease is an independent predictor of lymph node metastasis in patients with GISTs. Lymph node metastasis is also associated with worse overall survival in patients with metastatic GISTs.