Keywords
Gastrointestinal Stromal Tumor - GIST - rectum - surgical resection - immunohistochemistry
Introduction
A gastrointestinal stromal tumor (GIST) is a rare entity originating from the cells
of Cajal. Although their incidence is rare (14–20 per million), they are the most
common type of malignant mesenchymal tumors of the gastrointestinal tract. They are
most found in the stomach and small intestines but can arise at other sites. Of these,
∼ 5% are located primarily in the rectum.[1]
[2]
These tumors occur equally in both sexes, mostly in the sixth decade of life. No specific
risk factor has been identified, but people with neurofibromatosis type I are more
likely to develop a GIST, as are those with Carney triad[3] and those with a family history of stromal tumor. Gastrointestinal stromal tumors
do not appear to be associated with other malignancies.[4]
[5]
They cause unspecific symptoms depending on their location (early satiety, abdominal
distension, gastrointestinal disorders, bleeding, obstruction, among others).[6]
Rectal GISTs present with primary symptoms of hematochezia (23.0%), constipation (15.2%),
and anal pain (38.5%), similar to those of other rectal tumors.[7]
[8]
These tumors are usually diagnosed incidentally during a radiological or endoscopic
study, in which lesions of less than 10 mm to large lesions measuring more than 350 mm
can be observed.[9]
Gastrointestinal stromal tumors are considered specific entities that can be classified
into three categories according to their morphology: epithelioid, spindle cell, or
mixed.[10]
To confirm the diagnosis, an immunohistochemical study is necessary.[7] To be called GIST, they must be identified by mutations in the c-KIT receptor (the
most sensitive and specific marker) -present in 75 to 80%- and in the platelet-derived
growth factor receptor tyrosine kinase alpha (PDGRF-α).[11]
[12] present in 75 to 80% and in the PDGRF- α—present in 5 to 10%—these characteristics
are what cause GISTs.[6]
[13] These characteristics are what make them highly resistant to conventional chemotherapy
and radiotherapy. Tumors that do not have these mutations are called wild-type GISTs.[14]
As mentioned, these tumors are usually found incidentally; however, when their surgical
protocol is performed, computed tomography (CT) and positron emission tomography (PET)
scans are usually of great help. On CT, GISTs are usually seen as an exophytic mass
that enhances heterogeneously with intravenous contrast because of their high vascularity,
and PET can reveal small metastases and establish baseline metabolic activity, which
can later help in the evaluation of effectiveness of therapy. In the anorectal region,
magnetic resonance imaging (MRI) can be of great help due to the anatomical detail
it offers for planning the surgical approach.[7]
[15]
On the other hand, The Canadian Advisory Committee on Gastrointestinal Stromal Tumours
recommends that a follow-up CT scan be performed every 3 to 6 months for a minimum
of 5 years after resection in patients without residual disease.[16]
If there is a high suspicion that it is a GIST, biopsy is not recommended; however,
if it is an undetermined lesion in an accessible location, fine needle aspiration
or endoscopic biopsy are the methods of choice. Percutaneous biopsy is not recommended
because of the risk of dissemination. Open biopsy is indicated for inaccessible tumors.[17]
Surgical resection is preferred for the management of local disease. The objective
is complete macroscopic resection obtaining negative margins with preservation of
the pseudocapsule to avoid tumor dissemination.[18]
[19]
Particularly with GISTs arising in the rectum, total excision of the mesorectum is
the preferred approach. Resecting the lymph nodes along the mesenteric or mesorectal
vessels is not necessary.[1]
[20]
Prognosis after surgical resection is strongly affected by both tumor size and mitotic
activity.[21]
Presentation of the Case
We present the case of a 60-year-old male who was sent for consultation due to diarrhea
with 1 year and 6 months of evolution and weight loss of 30 kg in 1 year. He denied
bleeding or transrectal mucus output. On physical examination, the abdomen had a palpable
tumor in the right iliac fossa, not delimited, without peritoneal irritation; and
on rectal examination, a lesion was palpated, 5–6 cm from the anal margin, anterior,
renitent, and mobile. A biopsy was taken by anal exploration, which reported inadequate
material for diagnosis; thus, a colonoscopy was scheduled ([Fig. 1]), during which a biopsy was taken, which reported an ulcer bed with granulation
tissue without neoplasia and inadequate material.
Fig. 1 Tumor from 6 to 13 cm of anal margin, pedicle at 13 cm anterior left; without mucosal
alterations.
The patient was protocolized for surgery, and abdominopelvic CT scan ([Fig. 2]) and MRI ([Fig. 3]) were performed.
Fig. 2 Abdominopelvic computed tomography scan. Rectum – sigmoid-dependent tumor lesion
with apparent intussusception effect, heterogeneous content, 95 × 88 × 80 mm.
Fig. 3 Magnetic resonance imaging scan. Tumor lesion in upper and middle third of rectum
9.3 × 8.5 × 8.1 cm probably related to gastrointestinal stromal tumor. Lower third
of rectum and levator and sphincter complex muscles with preserved signal intensity.
The patient underwent elective ultra-low anterior resection with primary colorectal
anastomosis 5 cm from the margin of the anus ([Fig. 4]).
Fig. 4 Ultra-low anterior resection.
Pathology confirmed rectal GIST ([Fig. 5]) measuring 10 × 7.1 × 6.5 cm, pedunculated and ulcerated, with less than 1% mitoses
in 10 high-power fields, no neoplasia in proximal, distal, or radial surgical edges,
no vascular invasion, necrosis, or hemorrhage.
Fig. 5 Surgical specimen of ultra-low anterior resection of the middle, superior and sigmoid
rectum. Gastrointestinal stromal tumor measuring 10 × 7.1 × 6.5 cm, pedunculated and
ulcerated.
The result of the immunohistochemistry revealed CD117 positive, CD34 positive, AML
positive, PS100 negative, and Ki67 positive < 1% mitosis ([Fig. 6]).
Fig. 6 Immunohistochemical analysis. (A) CD34: positive (++); (B) AML: positive (++); (C) PS100: negative; (D) ki-67: positive < 1% mitosis.
Discussion
The cornerstone of treatment remains resection. For the treatment of advanced GIST,
imatinib, which is a small molecule tyrosine kinase inhibitor with activity against
Abelson leukemia virus (ABL), breakpoint cluster region (BCR)-ABL, stem cell factor
receptor (KIT), PDGFR-α, platelet-derived growth factor receptor beta (PDGFR-β), ARG,
and possibly colony-stimulating factor-1 receptor (CSF1R), is also indicated as neoadjuvant
or adjuvant therapy.[22]
Gastrointestinal stromal tumors are sensitive to imatinib by two mechanisms, as the
drug inhibits the activity of wild-type KIT kinase and the growth of a line of gastrointestinal
stromal tumor cells; however, if there is no response to treatment within 6 months,
we speak of a tumor with primary resistance.[23]
[24]
If the tumor is located in the rectum and is in an advanced stage, it is usually a
bulky entity. There is still no standardized technique, but a local resection (minimally
invasive transanal resection) can be performed, although its use is limited by the
distance to the dentate line, which must be close; a low anterior resection (LAR),
an abdominoperineal resection (APR) or even a pelvic exenteration.[7]
[25]
[26]
Consideration must be given to the confined pelvic space and the fact that the tumor
is often densely adherent to the pelvic floor, which can require cruciate surgery
to achieve a complete surgical resection.[20]
The cause of death following curative resection is distant metastasis rather than
local recurrence, with the most common site being the liver. Gastrointestinal stromal
tumors metastasize to lymph nodes only rarely. Almost all patients undergoing resection
for advanced disease have subsequent recurrence, regardless of the quality of the
procedure. It has been observed that the median survival of patients with advanced
disease is 18 to 24 months.[27]
[28]
Conclusion
Gastrointestinal stromal tumor is a rare but important entity, as it is the most common
type of mesenchymal tumor in the gastrointestinal tract. Although its incidence is
low, its diagnosis and management are critical due to its malignant potential and
resistance to conventional treatments such as chemotherapy and radiotherapy.
Gastrointestinal stromal tumors can occur in various locations of the gastrointestinal
tract, with the most common being the stomach and small intestine. Although no specific
risk factor has been identified, certain genetic conditions may increase the likelihood
of developing GIST.
The diagnosis is usually made incidentally during radiologic or endoscopic studies,
confirmed by immunohistochemical studies that identify mutations in c-KIT and PDGRF-α
receptors. Primary management involves surgical resection, aiming for complete removal
of the tumor. In advanced cases, imatinib therapy may be considered, although primary
resistance to treatment can be a challenge.
Despite curative resection, recurrence and distant metastasis are major concerns,
especially in the liver. Therefore, periodic long-term follow-up is recommended to
detect and treat possible recurrences.
Bibliographical Record
Nadab David Mitre-Reyes, Yulia Angélica Morales-Chomina, Luz del Carmen Mendoza Namur,
Alan Guerrero-Gomez, Kevin Joseph Fuentes-Calvo, Moises Freddy Rojas-Illanes. Gastrointestinal
Stromal Tumor (GIST) in the Rectum: A Rare Location. Journal of Coloproctology 2025;
45: s00451802978.
DOI: 10.1055/s-0045-1802978
