Submucosal Cecal Lipoma Mimicking Malignancy in a 51-Year-Old Man: A Diagnostic Challenge in Routine Colonoscopy

Introduction

Lipomas are benign tumors of fat cells (adipocytes) that present as soft, painless masses, which are most commonly seen on the trunk but can be located anywhere on the body [1–3]. Lipomas usually range from 1 to 10 cm. They are mesenchymal tumors and are found anywhere in the body where normal fat cells are present. Gastrointestinal lipomas are sporadic, slow-growing mesenchymal tumors that can develop throughout the entire gastrointestinal tract. While typically solitary, they can occasionally present as multiple lesions. Although histologically submucosal in origin, these benign neoplasms often protrude intraluminally, exhibiting a gross morphological resemblance to subcutaneous adipose tissue. Most lipomas are discovered incidentally; however, larger lesions (>2 cm) can develop a pseudopedicle and serve as lead points for intussusception. Additionally, ulceration – frequently observed in larger tumors – can result in chronic blood loss and iron-deficiency anemia. In cases complicated by intussusception, vascular compromise can precipitate acute hemorrhage, necessitating prompt intervention [4]. Colonic lipomas represent infrequent benign neoplasms of the gastrointestinal tract. Predominantly located in the ascending colon, these lipomas primarily manifest within the submucosal layer, with a mere 10% of cases presenting as multiple lesions. During endoscopic examination, most lipomas exhibit the “pillow sign” when touched with biopsy forceps. If a biopsy is taken using forceps, exposing the submucosal fat, the “naked fat sign” can also be observed [5]. Typically, their occurrence is observed in female patients during their fifth and sixth decades of life [6].

Colonic lipomas are benign masses typically found incidentally during routine colonoscopy screening. Despite their relative rarity, comprising only 0.2% to 4.4% of all colorectal neoplasms, the clinical significance of these tumors is considerable [7]. While most colonic lipomas are small and do not lead to complications, giant lipomas can present with symptoms ranging from changes in bowel patterns and mild abdominal pain to bowel obstruction. Ulcerated giant colonic lipomas are even rarer findings on screening colonoscopies [8]. These uncommon gastrointestinal tumors present diagnostic challenges due to their rarity and malignant-mimicking histological features. Current evidence supports both the complete surgical resection and endoscopic removal as viable treatment modalities with favorable outcomes [9,10]. This report describes the case of a 51-year-old man with a submucosal lipoma of the cecum diagnosed as an incidental finding during routine colonoscopy.

Case Report

On April 29, 2024, a 51-year-old man, who was asymptomatic, was found to have a tumor of unknown nature in the cecum during a routine colonoscopy screening. The size of the mass was approximately 1.5×2 cm, and the surface of the mass was ruptured. Tissue biopsy was taken under colonoscopy, and the pathological results suggested the formation of a tubular adenoma with ulceration. Considering the morphology and appearance of the cecal mass under colonoscopy, malignant transformation could not be ruled out. The patient had a strong desire for surgery and actively requested surgical resection treatment; therefore, he was admitted to our General Surgery Department on May 5, 2024. No significant positive physical signs were observed during the examination after admission. Routine preoperative blood, urine, stool, liver and kidney function, electrolyte, and coagulation function tests were not found abnormal. A-fetoprotein, carcinoembryonic antigen, and carbohydrate antigen 19-9 were within the normal range, and carbohydrate antigen 72-4 was increased to 14.50 kU/L. The surgeon recommended that the patient undergo a computed tomography (CT) scan to complete the preoperative evaluation. However, due to an iodine allergy, the patient declined the CT scan and requested to proceed directly with surgical treatment. On May 7, 2024, laparoscopic right hemicolectomy and peri-colonic lymph node dissection and mesenteric lymph node dissection and ileotranscolostomy were performed under endotracheal general anesthesia. The patient recovered well after surgery, and no significant complications were observed. The postoperative pathological results confirmed that the cecal mass was a lipoma with surface ulceration, and the patient had chronic appendicitis due to the lipoma’s growth position near the inner orifice of the appendix (Figurse 1, 2). We speculated that the cause of chronic appendicitis might have been related to the cecal tumor pressing on the inner orifice of the appendix during intestinal peristalsis. However, the patient did not have the classic symptoms of lower right abdominal pain.

Discussion

When endoscopy reveals a gastrointestinal subepithelial lesion, it needs to be observed closely and carefully. If the surface of the lesion changes and is not covered by intact normal mucosa, or if its size changes rapidly, more examination and treatment are needed [11]. Several characteristic diagnostic features facilitate the identification of colonic lipomas. The squeeze sign, considered pathognomonic on radiographic imaging, manifests as a radiolucent filling defect with well-defined margins that dynamically alters in size and shape due to peristalsis during barium enema examination. Endoscopically, the cushion sign (or pillow sign) is observed when applying forceps pressure induces a soft, indentation-resistant deformation of the lipomatous lesion. Additionally, the tenting sign is elicited when traction on the tumor surface produces a tent-like protrusion. Histopathologically, the naked fat sign confirms the diagnosis, characterized by the presence of mature adipocytes, without a fibrous capsule in biopsy specimens [9]. However, if there is erosion or ulceration on the surface of the subepithelial lesion, there are reasons to suspect that it is malignant or has malignant potential, such as gastrointestinal stromal tumors, neuroendocrine tumors, or cancer. In the present case, colonoscopy showed that the surface of the gastrointestinal submucosal tumor was ulcerated and covered with white necrosis. Therefore, we believed that this endoscopic presentation implied a malignant potential and was unlikely benign. In the meantime, the patient had a strong desire to surgically remove the lesion. We discussed with the patient and advised him to complete further examinations, such as an abdominal magnetic resonance imaging (MRI), endoscopic ultrasound, and positron emission tomography (PET) CT, before deciding on surgical treatment. However, given the patient’s limited financial resources and his question about whether an endoscopic ultrasound or abdominal MRI could definitively determine the nature of the tumor, we truthfully explained that imaging studies could provide only supportive evidence in assessing benign or malignant potential, and that the final diagnosis would still rely on endoscopic and pathological findings. Under these circumstances, the patient declined the additional imaging tests and ultimately opted to proceed directly with surgical intervention. Therefore, laparoscopic resection of the tumor was finally performed, and the final pathological diagnosis was lipoma, which was a surprising result. Colonic lipomas generally appear as round or hemispherical smooth surfaces, or submucosal masses with yellow envelopes [12,13]; however, these characteristics did not apply to this case. We suspect that the ulcers on the surface of the lipoma in this case may have been caused by friction between the movement of the bowel and the colonic contents.

The treatment of benign gastrointestinal lipomas depends on their clinical symptoms and size. If patients with gastrointestinal lipomas have no symptoms, monitoring these lesions is generally recommended. However, the primary treatment for patients with symptomatic gastrointestinal lipomas is surgery. If gastrointestinal lipomas can be removed by endoscopic resection, endoscopic therapy is an alternative for patients with symptomatic gastrointestinal lipomas [14].

With the advancement of medical technology, endoscopic resection of colonic lipomas has become increasingly common [15–17]. Compared with surgical resection, endoscopic removal offers advantages such as minimal trauma, faster recovery, lower costs, and shorter hospital stays. However, it is worth noting that some patients with colonic lipomas still undergo surgical resection. This is partly related to the accuracy of preoperative diagnosis, making more precise preoperative evaluation increasingly crucial.

Conclusions

In summary, we encountered a particular case of cecal lipoma that looked different from typical gastrointestinal lipomas. Therefore, we report an interesting and rare case of cecal lipoma, with the unique characteristic that the surface of the cecal mass was ulcerated during the endoscopy examination. At first, a tubular adenoma was pathologically considered by colonoscopy biopsy, but at last, a cecal lipoma with a surface ulcer was pathologically confirmed after right hemicolectomy. It was even more peculiar that the patient also had chronic appendicitis. It is worth noting that benign submucosal masses of the cecum can also present with various colonoscopy findings that look like malignant tumors, with or without symptoms. To further clarify the diagnosis, preoperative examinations, such as endoscopic ultrasound, abdominal CT/MRI, and even PET-CT can assist in further clarifying the diagnosis [18,19]. These diagnostic tools have a profound impact on the surgical approach and patient prognosis. Here, we need to reaffirm that appropriate imaging and shared decision-making are vital to preventing unnecessary surgical intervention. We hope this case serves as a reminder to everyone that benign submucosal lesions of the gastrointestinal tract are recognized to be a diagnostic challenge and can be confirmed only by excision and histopathology, as in this case.