One in Five GISTs at Tanzanian Hospital Lack SDHB, Study Finds

A new retrospective study from Muhimbili National Hospital in Tanzania reports that among 60 CD117-positive GISTs tested with SDHB immunohistochemistry, 12 cases, or 20.0 percent (95% CI, 11.8–31.8%), were SDHB-negative. The authors describe this as one of the first reports of SDHB-negative GISTs from a sub-Saharan African population, and the frequency they observed is higher than that reported in several previous series.

The study, published in BMC Gastroenterology, was conducted at the hospital’s Central Pathology Laboratory using archived formalin-fixed paraffin-embedded blocks from CD117-positive GISTs diagnosed between January 2015 and January 2022. The researchers extracted clinical and pathological variables from patient records and analyzed the data in SPSS version 23, using Fisher’s exact test to look for associations between SDHB status and factors such as age, sex, tumor location and histomorphological pattern, with a p-value below 0.05 considered statistically significant.

The patients ranged from 30 to 87 years old, with a mean age of 54.37 ± 14.6 years. SDHB negativity was distributed fairly evenly across age groups: 5 of 24 cases (20.8%; 95% CI, 9.2–40.5%) occurred in patients aged 50 years or younger, while 7 of 36 cases (19.4%; 95% CI, 9.8–35.0%) occurred in patients older than 50. Similarly, 6 of 36 tumors from male patients (16.7%; 95% CI, 7.9–31.9%) and 6 of 24 tumors from female patients (25.0%; 95% CI, 12.0–44.9%) were SDHB-negative.

Morphology also did not separate the two groups cleanly. Spindle-cell tumors showed SDHB negativity in 8 of 36 cases (22.2%; 95% CI, 11.7–38.1%), compared with 4 of 24 cases (16.7%; 95% CI, 6.7–35.9%) that had mixed epithelioid and spindle-cell features. By anatomical site, 7 of 34 gastric GISTs (20.6%; 95% CI, 10.3–36.8%) and 3 of 12 small-bowel GISTs (25.0%; 95% CI, 8.9–53.2%) were SDHB-negative, confirming that these tumors arise at both gastric and non-gastric locations.

Despite the numerical differences across subgroups, none of the comparisons reached statistical significance. The authors report that no statistically significant associations were identified between SDHB status and age, sex, anatomical site or histomorphological pattern, and they attribute this to the limited sample size rather than to evidence of a true absence of differences. Their conclusion notes a higher numerical trend for several of these variables but states explicitly that the small number of cases precluded statistical confirmation.

The clinical relevance of identifying SDHB-negative GISTs lies in how this subset is managed. According to the study’s background, SDHB-negative GISTs are readily diagnosed using immunohistochemistry and can be treated with second-line tyrosine kinase inhibitor targeted therapy when appropriate. The authors also note that GISTs in sub-Saharan African countries, including Tanzania, have been poorly researched with respect to prevalence, histomorphological features, clinical presentation and response to targeted therapy, which makes local frequency data directly useful for pathology practice in the region.

Methodologically, the study is a single-center retrospective cross-sectional analysis, which shapes what its results can and cannot show. Because it relied on archived diagnostic material from one tertiary hospital, covering cases diagnosed between January 2015 and January 2022, the 60 evaluable tumors represent the cases available at that laboratory rather than a population-based sample. The confidence intervals around each subgroup estimate are wide, in several cases spanning from under 10 percent to over 40 percent, reflecting the small numbers of cases within each stratum.

The authors themselves frame the work as a starting point rather than a definitive answer. They call for further large multicenter studies incorporating molecular testing to validate the observed frequencies and patterns. Such studies would be needed to determine whether the roughly one-in-five frequency seen at Muhimbili National Hospital holds across other African settings, and whether the apparent morphological and anatomical distributions reflect real biological variation or simply the play of chance in a small sample.

For now, the study’s key contributions are descriptive: it documents that SDHB-negative GISTs account for 20.0 percent of evaluable CD117-positive cases at this Tanzanian tertiary center, that they occur across a wide adult age range and in both sexes, and that they are found at both gastric and small-bowel sites. Within the constraints of its design, it provides a baseline frequency estimate for a tumor subgroup that had previously been poorly characterized in this region.

Subject of Research: The frequency and histomorphological features of SDHB-negative gastrointestinal stromal tumors at a Tanzanian tertiary hospital.

Article Title: Prevalence and morphology of SDHB-negative GISTs: insights from a Tanzanian tertiary center

Article References: Mavundla, J. A., Matiku, S. B., Liwa, E. A., Mwakigonja, A. R., Vuhahula, E., & Kabyemela, E. R. (2026). Prevalence and morphology of SDHB-negative GISTs: insights from a Tanzanian tertiary center. BMC Gastroenterology. https://doi.org/10.1186/s12876-026-05452-7

Image Credits: AI Generated

DOI: 10.1186/s12876-026-05452-7

Keywords: GIST, SDHB, immunohistochemistry, Tanzania, Muhimbili National Hospital, retrospective study, gastrointestinal stromal tumors, pathology, spindle-cell morphology, tyrosine kinase inhibitors, sub-Saharan Africa, BMC Gastroenterology