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Gastrointestinal stromal tumors (GISTs) are sarcomas affecting the stomach and small intestine, with a rare subtype characterized by succinate dehydrogenase B (SDHB)-loss posing significant diagnostic and therapeutic challenges. A 62-year-old man with weight loss and abdominal pain was diagnosed with a gastric GIST showing SDHB-loss. Initial treatment with Imatinib reduced the tumor size, but surgery revealed no residual tumor. Despite adjuvant Imatinib, recurrence occurred, necessitating further surgical intervention. While GISTs typically benefit from surgery and tyrosine kinase inhibitors (TKIs), those with SDHB-loss are resistant to TKIs, requiring a different management approach. This case emphasizes the importance of surgical intervention for SDHB-deficient GISTs and the need for ongoing research into effective treatments for this subtype.

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Background Gastrointestinal stromal tumors (GISTs) arise from Cajal's interstitial cell precursors and display a variety of genetic mutations, primarily in the KIT and PDGFRA genes. These mutations are linked to tumor location, prognosis, and response to treatment. This study delves into the mutational patterns of GISTs in a Mexican population and their impact on overall survival (OS) and disease-free survival (DFS). Methodology This retrospective study examined 42 GIST cases diagnosed at the Oncology Hospital of the National Medical Center XXI Century between January 2018 and December 2020. Clinical, histological, and immunohistochemical data were gathered, and mutational analysis of KIT and PDGFRA genes was conducted using second-generation sequencing. Results The study group consisted of 52.4% females and 47.6% males, with an average age of 62.6 years. The most common tumor site was the stomach (59.5%), followed by the small intestine (26.2%). KIT mutations were detected in 71.4% of cases, predominantly involving exon 11. PDGFRA mutations were observed in 7.1% of cases. Recurrence was noted in 9.5% of patients, all with high-risk tumors. No significant link was identified between specific mutations and OS or DFS. Conclusions This investigation sheds light on the genetic landscape of GISTs in the Mexican population. While no significant association was established between particular mutations and survival outcomes, the study emphasizes the importance of molecular profiling in treatment decision-making. Further studies with larger sample sizes and longer follow-up periods are necessary to validate these results and explore their clinical relevance.

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RESUMEN El tumor estromal gastrointestinal es el tumor mesenquimático más frecuente y se caracteriza por la expresión de un receptor de factor de crecimiento tirosina kinasa, CD117 c-KIT/CD 117. Se diferencia del resto de los tumores mesenquimáticos en que no expresa esta proteína. Alrededor del 70 - 80 por ciento de estos tumores son benignos, la mayoría se localizan en estómago e intestino delgado (> 90 por ciento). Los tumores estromal gastrointestinal malignos son generalmente de gran tamaño (> 5 cm), con índice mitótico alto y pueden dar metástasis a hígado y peritoneo. El tratamiento es la resección quirúrgica. Presentamos una paciente con 65 años de edad que acudió al cuerpo de guardia por sufrir caída de sus pies y quejarse de dolor abdominal. Como datos positivos al examen físico se constató palidez cutáneo mucosa y los complementarios de urgencia. El ultrasonido y la tomografía axial computarizada informaron líquido libre en cavidad con cifras de hemoglobina en 6,4 g/L. La punción abdominal constató sangre roja que no coagulaba. Se realizó laparotomía exploratoria encontrando hemoperitoneo y gran tumoración en cara anterior del antro gástrico, con otra pequeña en la porción alta del cuerpo; se realizó resección local con bordes libres de tumor y se suturaron los bordes gástricos. El resultado de la biopsia informó tumor del estroma gastrointestinal de células fusiformes con bajo índice mitótico, que midió 13 x 8 x 8 cm, con marcada angiogénesis y zonas de calcificación(AU)

ABSTRACT Gastrointestinal stromal tumor is the most frequent mesenchymal tumor and is characterized by expression of a tyrosine kinase growth factor receptor, CD117 c-KIT/CD 117. It is different to the rest of mesenchymal tumors in that it does not express this protein. About 70-80 percent of these tumors are benign. The majority are located in the stomach and small intestine (more than 90 percent). Malignant gastrointestinal stromal tumors are usually large (over 5 cm in size), with a high mitotic index, and can metastasize to the liver and peritoneum. The treatment is surgical resection. We present a 65-year-old patient who came to the emergency room due to having fallen on her own feet and complaining of abdominal pain. As positive data to the physical examination, mucous and skin whitening and the emergency complement tests were analyzed. Ultrasound and CT scan reported free fluid in cavity with hemoglobin values at 6.4 g/L. The abdominal puncture showed red blood that did not clot. The exploratory laparotomy showed a hemoperitoneum and a large tumor in the anterior face of the gastric antrum, with a small one in the upper portion of the body; local resection with tumor-free borders was performed and the gastric borders were sutured. The result of the biopsy reported a spindle cell gastrointestinal stromal tumor with a low mitotic index, measuring 13x8x8 cm, with marked angiogenesis and areas of calcification(AU)

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Cuando tenemos un tumor óseo maligno del fémur distal con contaminación de la articulación, ya sea por extensión del tumor, fracturas secundarias al tumor con trazo intraarticular o contaminación en una biopsia tomada de manera inadecuada, debemos realizar resecciones extraarticulares de rodilla para lograr un control primario del tumor. Podemos emplear varias técnicas para lograr este fin, y una buena reconstrucción; la técnica que empleamos es la resección extraarticular más la preservación del mecanismo extensor, poco conocida en nuestro medio y de la cual es pionera el instituto Nacional de Cancerología. Con ella, hemos logrado un adecuado control tumoral primario de las lesiones óseas malignas en el fémur distal, menor número de complicaciones, una rápida rehabilitación y retorno a sus actividades habituales. Por esto, el interés de dar a conocer dicha técnica en los grupos de ortopedia oncológica, para que haga parte de su armamentario quirúrgico habitual.

When we encounter a malignant bone tumor in the distal femur with contamination of the joint, whether caused by tumor extension, secondary tumor fractures with intra-articular traces, or by contamination produced by inadequate taking of biopsies, extra-articular knee resection must be performed in order to achieve primary tumor control. Several methods are at our disposal to do so; our reconstruction technique of choice is that of extra-articular resection plus preservation of the extensor mechanism. this method is not well known locally; however, the National Cancer institute of Colombia has pioneered its use, thus allowing us to attain adequate primary tumor control in malignant bone lesions in the distal femur, with fewer complications, rapid rehabilitation and more immediate return to daily activities. We are, therefore, interested in sharing our expertise on this method with orthopedic oncologists so that they may include it their armory of standard surgical procedures.

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