Transverse colon foreign body-associated reactive mass mimicking gastrointestinal stromal tumors: A case report

Abstract

BACKGROUND

Foreign body-associated reactive masses may appear months to decades after abdominal surgery and often present as well-circumscribed lesions on imaging studies. Their radiological features frequently mimic gastrointestinal stromal tumors (GISTs) or other malignant intra-abdominal neoplasms. While most reported postoperative foreign body reactions arise in the peritoneal cavity or mesentery, reactive masses originating from the colonic wall are exceptionally rare. Large colonic lesions presenting many years after surgery further complicate diagnosis.

CASE SUMMARY

A 38-year-old man with a history of open appendectomy 20 years prior was incidentally found to have a 9-10 cm intra-abdominal mass on a subsequent computed tomography (CT) screening. Contrast-enhanced CT presented a well-circumscribed lesion with marked central low attenuation and peripheral enhancement, strongly suggestive of a GIST in the small bowel. Exploratory laparotomy revealed a firm, heterogeneous mass densely adherent to adjacent structures and arising from the transverse colon. Thus, segmental transverse colectomy with stapled anastomosis was performed. Histopathological examination showed extensive fibrosis, necrosis, and old hemorrhage with a chronic foreign body-type reactive process and no neoplastic features. No grossly identifiable foreign material was detected, although microscopic findings supported a chronic foreign body reaction. Postoperative recovery was uneventful aside from a brief readmission for transient ileus.

CONCLUSION

Colonic foreign body-associated reactive masses can mimic GISTs decades after surgery and should be considered in patients with prior abdominal operations.

Key Words: Foreign body-associated reactive mass; Gossypiboma; Transverse colon; Gastrointestinal stromal tumor mimic; Postoperative reactive process; Case report

Core Tip: We report a rare case of a large foreign body-associated reactive mass presenting 20 years after surgery for perforated appendicitis. The lesion mimicked a gastrointestinal stromal tumor on contrast-enhanced computed tomography, leading to diagnostic uncertainty. Surgical resection and histopathological evaluation revealed a chronic foreign body-type inflammatory reaction, in which microscopic foreign materials were identified despite the absence of a grossly identifiable foreign body. This case illustrates a potential diagnostic pitfall and emphasizes the need to consider postoperative inflammatory and foreign body-associated lesions in the differential diagnosis of large intra-abdominal masses.

INTRODUCTION

Foreign body-associated reactive masses arising in the abdominal cavity are uncommon but clinically significant, as these masses often mimic malignant tumors on cross-sectional imaging[1-4]. Retained surgical materials, such as sponges (gossypiboma or textiloma), account for the majority of reported cases; however, non-textile foreign bodies and chronic postoperative changes, such as organizing hematomas, may generate similar foreign body reactions[5,6]. The true incidence is underestimated due to medicolegal concerns, although prior studies have indicated an occurrence of approximately 1 in 1000-1500 abdominal surgeries, with notable morbidity and occasional mortality[5].

These lesions frequently mimic gastrointestinal stromal tumors (GISTs), soft-tissue sarcomas, ovarian neoplasms, or lymphomas[1-4,7]. Indeed, imaging characteristics, including peripheral enhancement, central necrosis, and well-defined margins, closely resemble those of GISTs, thereby making preoperative diagnosis particularly challenging[1,2,8]. Most reported foreign body-associated reactive masses occur in the small bowel mesentery, pelvis, or retroperitoneum[3,4,6]; involvement of the colon is exceptionally rare[8,9].

We present a unique case of a large transverse colon foreign body-associated reactive mass that developed 20 years after an open appendectomy and strongly mimicked a GIST on contrast-enhanced computed tomography (CT). To our knowledge, reports of colonic foreign body-related reactive masses of this size with such a prolonged latency are exceedingly rare. Thus, this case highlights critical diagnostic pitfalls and underscores the need to consider foreign body reactions in the differential diagnosis of abdominal masses in patients with remote surgical histories.

CASE PRESENTATION

Chief complaints

A 38-year-old man was referred for evaluation of an incidentally detected intra-abdominal mass identified on a chest CT scan performed during routine health screening.

History of present illness

The patient was asymptomatic at the time of detection. He denied abdominal pain, distension, nausea, vomiting, changes in bowel habits, gastrointestinal bleeding, weight loss, fever, or other systemic symptoms. The mass was discovered incidentally, and he remained clinically stable up to the time of surgery.

History of past illness

The patient had no medical comorbidities. His only prior abdominal surgery was an open appendectomy performed 20 years earlier at another hospital for perforated appendicitis complicated by peritonitis.

Personal and family history

The patient had no significant personal history of smoking, alcohol use, or occupational exposures. There was no family history of gastrointestinal malignancy or other hereditary diseases.

Physical examination

On physical examination, a firm, palpable mass was noted in the right upper quadrant without tenderness or signs of peritoneal irritation. The abdomen was otherwise soft and nondistended. Vital signs were within normal limits.

Laboratory examinations

Laboratory evaluation revealed no abnormalities. Complete blood count, liver function tests, renal function tests, and routine blood biochemistry were all within normal ranges.

Imaging examinations

An abdominal contrast-enhanced CT revealed a well-circumscribed mass of approximately 10 cm located in the small bowel mesentery (Figure 1). The lesion demonstrated markedly low attenuation in the central portion with a solid, enhancing peripheral rim, creating a radiological appearance highly suggestive of a GIST. The mass was tightly abutting adjacent ileal loops, raising suspicion of a mural or mesenteric origin. There were no associated liver lesions, ascites, or lymphadenopathy, and no other abnormal intra-abdominal findings were identified.

Figure 1 Contrast-enhanced abdominal computed tomography images. A: Axial view. The orange arrow indicates the mass closely abutting the adjacent small bowel loops; B: Coronal view. Two orange arrows indicate the lesion at multiple points where it is in close proximity to the small bowel, which contributed to the initial interpretation of a small bowel-originating mass.

FINAL DIAGNOSIS

Gross examination of the resected specimen revealed a well-circumscribed subserosal mass arising from the transverse colon, measuring 9.7 cm × 8.0 cm × 7.5 cm (Figure 2A). The external surface of the mass was smooth and glistening with a pale tan appearance, with focal areas of discoloration consistent with old hemorrhage. On the opposite aspect, the mass showed irregular nodularity and dense fibrotic tissue firmly adherent to the adjacent colonic wall and mesentery, correlating with the marked adhesions observed intraoperatively (Figure 2B). No grossly identifiable foreign material was detected on initial inspection.

Figure 2 Gross appearance of the resected mass. A: Smooth, glistening external surface with pale tan coloration; B: Opposite surface with irregular nodularity and dense fibrotic adhesions.

On gross examination of the opened specimen, the colonic mucosa was intact, and a large subserosal mass measuring approximately 10 cm in maximal diameter was identified (Figure 3A). On sectioning, the mass was revealed as a unilocular cyst with a thick fibrous capsule, filled with yellowish, friable, dirty materials adherent to the inner wall (Figure 3B).

Figure 3 Gross pathological findings of the colonic subserosal mass. A: The specimen shows colonic mucosa with a subserosal mass measuring approximately 10 cm in diameter; B: On sectioning, the mass is revealed as a unilocular cyst with a fibrous capsule, containing yellowish, friable, dirty materials adherent to the inner wall.

Microscopically, low-power examination demonstrated a thick fibrous cyst wall located within the subserosal layer and attached to the pericolic adipose tissue (Figure 4A). The cyst lacked an epithelial lining, and the wall was composed of densely hyalinized collagen with mild chronic inflammatory cell infiltration, including lymphocytes and histiocytes. Scattered cholesterol crystals were identified within the cyst wall and intracystic contents, accompanied by a foreign-body-type granulomatous reaction. High-power examination revealed dense fibrosis with focal infiltration of macrophages and other chronic inflammatory cells (Figure 4B). The cystic cavity was filled with amorphous necrotic debris and numerous macrophages containing cholesterol clefts. Periodic Acid-Schiff (PAS) staining of the intracystic contents highlighted irregularly shaped foreign materials, including polygonal or mesh-like structures, within the necrotic debris (Figure 4C). These findings were consistent with a chronic foreign-body reaction rather than a true neoplastic process.

Figure 4 Histopathological features of the subserosal cystic lesion with foreign-body reaction A: Low-power microscopic examination demonstrates a thick fibrous cystic wall in the subserosa, filled with necrotic materials. Cholesterol crystals (arrow) with an accompanying foreign-body reaction are noted; B: High-power magnification of the cyst wall reveals dense fibrosis with mild chronic inflammatory cell infiltration. The cystic cavity contains numerous macrophages, amorphous necrotic debris with cholesterol crystals (arrow); C: Periodic Acid-Schiff staining of the intracystic contents highlights irregularly shaped foreign materials (arrow).

TREATMENT

A midline laparotomy was first performed by a gastrointestinal surgeon, who encountered extensive intra-abdominal adhesions. Upon exploration, a firm and heterogeneous mass measuring approximately 10 cm was identified in the right upper quadrant. The lesion was densely adherent to the omentum, small bowel mesentery, and retroperitoneum, making dissection difficult. As adhesiolysis progressed, the tumor was found to originate from the transverse colon rather than the small bowel, prompting intraoperative consultation with the colorectal surgery team.

Following identification of the mass as colonic in origin, the colorectal surgeon formally assumed responsibility for the procedure and proceeded with the definitive resection. After confirming the operative field, the ascending colon was mobilized, during which dense adhesions likely related to the prior appendectomy on the patient were encountered and meticulously released. A segmental resection of the transverse colon, including the mass, was then performed. The bowel was divided approximately 5 cm proximal and distal to the lesion using an 80 mm linear stapler, and a functional end-to-end stapled anastomosis was created. Minor intraluminal bleeding along the stapler line was controlled with sutures, and the enterotomy was closed in two layers using a monofilament absorbable suture, with additional seromuscular reinforcement as needed. A drain was placed in the right paracolic gutter for postoperative monitoring.

OUTCOME AND FOLLOW-UP

The patient recovered uneventfully and was discharged on postoperative day 7. He was readmitted the following day with nausea and vomiting; a subsequent abdominal radiography suggested postoperative ileus. Conservative management was successful, and he was discharged after 5 days. At the first postoperative outpatient visit, the patient expressed relief that the lesion was not a GIST and reported high satisfaction with the overall outcome. A chronological summary of the clinical course, diagnostic evaluations, operative management, and final pathology is presented in Table 1.

Table 1 Timeline of clinical events.

Time point	Event	Details
20 years prior	Open appendectomy	Performed for perforated appendicitis with peritonitis; no subsequent symptoms for two decades
Screening period	Screening chest CT	Incidentally detected a 9-10 cm intra-abdominal mass; patient asymptomatic
Diagnostic evaluation	Contrast-enhanced abdominal CT	Well-circumscribed mass with central low attenuation and peripheral enhancement, strongly suggestive of a GIST
Day of surgery	Exploratory laparotomy	Dense adhesions present; mass originated from the transverse colon rather than the small bowel
Same operation	Segmental transverse colectomy	Mass and involved colon resected; stapled functional end-to-end anastomosis performed
Postoperative day 7	Initial discharge	Early recovery uneventful
Postoperative day 8	Readmission	Nausea and vomiting; imaging suggested postoperative ileus; managed conservatively
Postoperative day 13	Final discharge	Symptoms resolved; no further complications
Postoperative pathology	Final diagnosis	Well-circumscribed 9.7 cm × 8.0 cm × 7.5 cm subserosal mass arising from the transverse colon; unilocular cystic lesion with a thick fibrous capsule, containing necrotic debris and old hemorrhage. No epithelial lining or neoplastic cells identified. Histology demonstrated cholesterol crystals and chronic foreign body-type inflammatory reaction, with PAS-positive irregular foreign materials detected microscopically, despite no grossly identifiable foreign material

CT: Computed tomography; GIST: Gastrointestinal stromal tumor.

DISCUSSION

Foreign body-associated reactive masses represent an important yet underrecognized postoperative complication, as their clinical and radiological features often mimic intra-abdominal malignancies. Retained surgical textiles, including gossypiboma or textiloma, are the most frequently reported etiology. The largest multi-case series identified 15 cases among more than 45000 abdominal operations, with considerable morbidity and a mortality rate of 13.3%[5]. Comparative analyses with data from other countries, including high- and low-income settings, have demonstrated substantial international variability in reported incidence; however, medicolegal concerns likely contribute to significant underreporting, suggesting that the true incidence is higher.

A characteristic feature of foreign body-associated reactions is their wide latency spectrum. While some series report symptom onset within months to years, multiple case reports describe delays of several decades, including jejunal gossypiboma 20 years after cesarean section, hepatic textiloma nearly 30 years after cholecystectomy, and suture granuloma more than 50 years after appendectomy[1,5,7,8]. The 20-year interval observed in our patient is consistent with these reports and underscores the importance of considering remote surgical history as a potential cause of late-presenting reactive masses.

Radiologically, foreign body-associated reactive masses are particularly deceptive. CT frequently demonstrates a well-defined mass with peripheral rim enhancement and heterogeneous or low-attenuation central change-features highly suggestive of GISTs or other soft-tissue malignancies[2,3,10]. While GISTs typically appear as predominantly solid enhancing masses with exophytic growth from the bowel wall, foreign body-associated granulomas more commonly demonstrate a cystic or necrotic center with a thick fibrous capsule; however, extensive adhesion to adjacent bowel loops may obscure the true site of origin, as in the present case. Magnetic resonance imaging may further show thick, irregular peripheral enhancement and T2 heterogeneity mimicking sarcoma, whereas positron emission tomography-CT may demonstrate variable fluorodeoxyglucose uptake related to chronic inflammatory activity, raising suspicion of recurrence or metastatic disease[6,7]. Consequently, such lesions have frequently been misinterpreted as GISTs, ovarian teratomas, lymphomas, or sarcoma-like reactions associated with embolic material[1,2,4,8,11]. These recurring diagnostic pitfalls are summarized in Table 2.

Table 2 Reported cases of foreign body-associated reactive masses mimicking tumors.

Ref.	Age (year)/sex	Symptoms	Preoperative imaging	Initial suspected diagnosis	Surgical method	Prior surgery and interval
Papaoikonomou et al[1]	42/female	Incidental finding	CT	GIST	Mass resection	Cesarean section, approximately 20 years
Han et al[2]	33/female	Vomiting	CT	Jejunal tumor (GIST)	Laparoscopy-assisted resection	Cesarean section, 7 years
Gaylard et al[7]	Adult	Asymptomatic PET-positive lesion	PET-CT	Lymphoma recurrence	Excisional resection	Appendectomy, 56 years
Itoh et al[6]	74/male	Incidental nodules	CT, PET-CT	Peritoneal metastasis	Liver + peritoneal nodule resection	Low anterior resection, 1.5 years
Celik et al[3]	Adult	Abdominal/pelvic mass	CT	Soft-tissue tumor	Laparotomy + mass excision	Abdominal surgery (unknown interval)
Hajri et al[8]	65/female	Nausea, vomiting	CT	GIST	Segmental hepatectomy	Cholecystectomy, 29 years
Zhang et al[4]	Female	Adnexal mass symptoms	CT	Ovarian teratoma	Mass excision + bowel resection	Abdominal surgery (unknown interval)
Oran et al[10]	28/female	Epigastric mass	CT	Serous cystadenocarcinoma	Laparotomy + mass removal	Cholecystectomy, 3 years
Oran et al[10]	36/female	Abdominal mass	CT	Ovarian/adnexal tumor	Laparotomy + mass removal	Cesarean section, (unknown interval)
Eken et al[9]	62/female	Abdominal discomfort	CT, MRI	Mesenchymal tumor	Mass resection	Prior abdominal surgery (unknown interval)
Fumimoto et al[11]	77/male	Asymptomatic	CT	Lymphoma vs sarcoma	Image-guided biopsy → conservative	NBCA embolization, 12 months

CT: Computed tomography; GIST: Gastrointestinal stromal tumor; PET-CT: Positron emission tomography-computed tomography; MRI: Magnetic resonance imaging; NBCA: N-butyl-2-cyanoacrylate (embolization material).

Postoperative inflammatory pseudocyst (PIP) is an important differential diagnosis, as it is a chronic cystic lesion characterized by a fibrous wall, absence of epithelial lining, and intracystic necrotic debris following abdominal surgery or peritonitis[7,12]. These features were present in our case, and the history of perforated appendicitis supports a postoperative inflammatory background. However, the identification of irregular PAS-positive foreign materials within the necrotic contents, together with cholesterol crystals and a foreign body-type reaction, favors a chronic foreign body–associated process rather than conventional PIP[6,8]. Although no gross foreign material was identified, long-standing foreign substances may fragment over time and persist only as microscopic remnants[1,10]. Accordingly, this lesion is best classified as a foreign body-associated reactive mass within the postoperative inflammatory spectrum.

Ingestion-related foreign body reactions were also considered, as sharp objects such as fish bones or toothpicks may perforate the colon and form tumor-like inflammatory masses[12-15]. These lesions typically occur in older patients with diverticulosis and most commonly involve the sigmoid colon or cecum. In the present case, an ingestion-related mechanism was unlikely due to the patient’s young age, absence of diverticular disease, lack of linear high-density structures on CT, and histological findings of chronic fibrosis and necrosis without food-related material. In addition, the transverse colon is an uncommon site for foreign body impaction, further arguing against this etiology.

This case highlights that foreign body-associated reactive masses may present decades after abdominal surgery and closely mimic GISTs or other solid tumors. Although ingestion-related foreign body reactions should be considered, large colonic masses lack reliable nonsurgical methods to exclude malignancy. Awareness of these diagnostic limitations is essential, and patients should be counseled regarding the need for surgical resection and the possibility of benign pathology despite suspicious imaging findings.

CONCLUSION

We report an exceptionally rare case of a transverse colon foreign body-associated reactive mass mimicking a GIST, presenting two decades after appendectomy. Although preoperative imaging strongly suggested a neoplastic process, the lesion proved benign. Surgeons should retain a high index of suspicion for foreign body-related reactive masses in patients with any history of abdominal surgery and be mindful that large masses of this nature ultimately require surgical resection for definitive diagnosis. Overall, clear communication with patients regarding these diagnostic uncertainties and the necessity of surgery is essential.