Inflammatory myofibroblastic tumor on second portion of duodenum: a case report

Abstract

Inflammatory myofibroblastic tumors (IMTs) of the duodenum are exceptionally uncommon, and their epidemiologic and clinical characteristics remain poorly defined because of the limited number of reported cases. We previously reported a case of duodenal IMT in the Korean Journal of Gastroenterology in 2018, with follow-up data available only up to 12 months. IMTs typically behave in a benign manner, but they may occasionally demonstrate local invasiveness and recurrence; therefore, achieving complete surgical excision is crucial, followed by long-term surveillance. In the present manuscript, we provide a subsequent long-term follow-up report of the same patient, offering an extended 88-month postoperative course and additional radiologic and pathologic details not included in the earlier publication. This follow-up report highlights the long-term benign behavior of the tumor despite positive surgical margins and anaplastic lymphoma kinase (ALK)-negative immunohistochemistry, contributing meaningful information to the scarce literature on adult duodenal IMTs.

INTRODUCTION

Inflammatory myofibroblastic tumors (IMTs) are uncommon mesenchymal neoplasms defined by the proliferation of myofibroblastic spindle cells accompanied by a variable inflammatory infiltrate composed mainly of plasma cells, lymphocytes, and eosinophils [1]. These tumors may develop in a wide range of anatomic sites that contain mucosal or serosal surfaces, including the respiratory, gastrointestinal, and genitourinary tracts, as well as the orbit and oral cavity. IMTs tend to occur predominantly in children and young adults and often appear as intra-abdominal masses involving the gastrointestinal tract. While most IMTs behave in an indolent manner, local recurrence occurs in up to one-quarter of cases, and distant metastasis, though rare (<5%), has been described in the lung, brain, liver, and bone [2–4]. In the United States, approximately 150 to 200 new cases are reported annually, and the overall epidemiologic profile of IMTs remains insufficiently characterized [5]. Clinically, patients with IMT often present with nonspecific manifestations, including abdominal pain, a palpable mass, or symptoms related to gastrointestinal obstruction. Systemic findings such as fever, weight loss, night sweats, and general malaise may also be observed. Immunohistochemically, the neoplastic cells typically express vimentin and show variable positivity for smooth muscle actin (SMA), muscle-specific actin, and desmin [4]. In contrast, they are negative for cluster of differentiation (CD)117 and frequently exhibit anaplastic lymphoma kinase (ALK) expression as a result of gene rearrangement at chromosome 2p23 [6]. This manuscript serves as a subsequent long-term follow-up report of a case we previously published in 2018 in the Korean Journal of Gastroenterology [7], providing extended 88-month clinical, radiologic, and pathological information that was not available in the initial report.

CASE REPORT

A 49-year-old man was referred to our hospital after an incidental detection of a submucosal duodenal mass with surface ulceration during esophagogastroduodenoscopy (EGD). The patient had a notable history of chronic alcohol intake of approximately 150 g per day. On physical examination, no remarkable abnormalities were observed. Routine laboratory studies, including serum tumor markers carcinoembryonic antigen and carbohydrate antigen 19–9, yielded results within normal limits. Endoscopic examination demonstrated an ulcerated lesion in the second portion of the duodenum (Fig. 1). Contrast-enhanced computed tomography (CT) revealed a 2.0 cm hypervascular lesion in the second portion of the duodenum (Fig. 2A). Additional findings included focal gallbladder wall thickening—most prominent at the neck—and a 6 cm cystic lesion in the right perirenal region. On magnetic resonance imaging, the lesion showed low signal intensity on both T2- weighted and T1-weighted sequences (Fig. 2B and C) and demonstrated persistent enhancement across dynamic contrast-enhanced phases (Fig. 2D–F).

Fig. 1.

Endoscopic image showing ulcerative lesion in the duodenum.

Fig. 2.

Contrast-enhanced CT and MRI findings of a duodenal mass. (A) Contrast-enhanced CT image showing a 2.0 cm-sized hypervascular mass (arrow) in the second portion of the duodenum. (B) Axial T2-weighted MRI demonstrating low signal intensity of the duodenal mass (arrow). (C) Axial T1-weighted MRI showing low signal intensity of the mass (arrow). (D–F) Contrast-enhanced MRI reveals persistent enhancement of the mass (arrow) across dynamic phases. CT, computed tomography; MRI, magnetic resonance imaging.

Based on these imaging characteristics, the preoperative differential diagnosis included a duodenal gastrointestinal stromal tumor (GIST), gallbladder adenomyomatosis, and urinoma. The patient subsequently underwent duodenal wedge resection with concurrent cholecystectomy and right ureteral double-J stent placement. Intraoperatively, the mass was found adjacent to the superior mesenteric vein and surrounded by dense fibrosis and inflammatory changes within the retropancreatic region. On postoperative pathological examination, a well-defined submucosal mass measuring 2.7×2.3×1.3 cm was identified. The mucosal resection margin measured less than 0.1 cm, and the radial margin was abutting the tumor, indicating a positive surgical margin. No lymphovascular invasion or necrosis was identified. The cut surface appeared yellowish-white and solid without evidence of necrosis or hemorrhage (Fig. 3A). Microscopically, the lesion consisted of a submucosal proliferation of spindle to stellate myofibroblastic cells arranged in loose fascicles within a fibromyxoid stroma (Fig. 3B). The tumor cells exhibited vesicular nuclei, eosinophilic cytoplasm, and occasional prominent nucleoli. A dense inflammatory infiltrate composed mainly of plasma cells and lymphocytes was distributed throughout the stroma. The annotated microphotograph (Fig. 3C) highlights these characteristic features, indicating the spindle cell component and the plasma cell–rich inflammatory areas for improved histologic correlation. Immunohistochemically, the tumor cells were positive for SMA and mouse double minute 2 homolog (MDM2) but negative for desmin, S100 protein, and CD117 (c-Kit). They were also negative for ALK1, discovered on GIST 1 (DOG1), CD34, synaptophysin, CD21, CD30, epithelial membrane antigen, and pan-cytokeratin. The postoperative course was uneventful, and the patient was discharged on the 10th postoperative day.

Fig. 3.

(A) Gross finding: a submucosal tumor mass, measuring 2.7×2.3×1.3 cm, is seen and the cut surface is yellowish-white and solid. Necrosis or hemorrhage is not observed. (B) Microscopic finding: tumor shows a submucosal tumor mass (hematoxylin and eosin [H&E], ×10). (C) Histopathological features of inflammatory myofibroblastic tumor. The lesion is composed of fascicles of spindle-shaped myofibroblastic cells with vesicular nuclei and eosinophilic cytoplasm embedded in a fibromyxoid stroma (blue box). A dense inflammatory infiltrate, predominantly composed of plasma cells and lymphocytes, is interspersed among the tumor cells (red box) (H&E, ×200).

Twenty months after the initial surgery, follow-up CT revealed a 13 cm mass at the lower pole of the right kidney. Histologic examination of the biopsy specimen demonstrated spindle cell proliferation consistent with a low-grade malignant neoplasm. Because surgical management was performed at another institution, it could not be definitively determined whether the lesion represented a recurrence of the primary IMT or a newly developed retroperitoneal sarcoma. The patient subsequently underwent right nephrectomy and has remained free of recurrence for 88 months after the operation. Compared with the previous publication, which included only 12 months of follow-up, the present report provides an extended 88-month postoperative course, including detailed long-term clinical outcomes and surveillance findings that were not available in the initial report.

DISCUSSION

IMT has been referred to by several historical terms, including inflammatory pseudotumor, plasma cell granuloma, pseudosarcoma, and myofibroblastic proliferation [8]. According to the current World Health Organization classification, IMT is defined as a fibroblastic or myofibroblastic neoplasm of intermediate biological potential, characterized by a low but distinct risk of malignant behavior. Extrapulmonary IMTs most frequently develop within the abdominal cavity, particularly in the mesentery and omentum. Involvement of the duodenum is extremely uncommon, with only a few cases documented to date (Supplementary Table 1) [8]. Clinically, IMTs of the duodenum may present with nonspecific gastrointestinal symptoms such as abdominal pain, nausea, vomiting, dyspepsia, or jaundice. Gastrointestinal bleeding can also occur when mucosal ulceration is present. In the present case, the lesion was incidentally identified during routine EGD as a submucosal mass with surface ulceration.

On radiologic evaluation, IMTs typically appear as lobulated or heterogeneous solid masses, which may or may not contain calcifications depending on the proportion of fibrous tissue and cellular density [8]. In the present case, contrast-enhanced CT demonstrated a well-circumscribed lesion with heterogeneous enhancement, while EGD revealed a submucosal mass with surface ulceration. Differentiating the lesion from a GIST before surgery was challenging due to overlapping imaging characteristics. Because of the rarity of IMT, standardized treatment guidelines have not yet been clearly defined. Nevertheless, complete surgical resection remains the cornerstone and most reliable curative option. Patients who undergo total excision generally have a favorable prognosis. In contrast, incomplete removal or lack of ALK expression has been linked to higher rates of local recurrence or distant metastasis, although ALK positivity itself does not consistently correlate with tumor relapse [9]. In cases where complete resection is not achievable, or in patients presenting with recurrent or metastatic disease, adjuvant or systemic therapy may be appropriate. Both chemotherapy and radiotherapy have been applied with variable outcomes in individuals with residual or advanced tumors [10,11]. Furthermore, several reports have suggested that nonsteroidal anti-inflammatory drugs, especially cyclooxygenase-2 inhibitors, can exert tumor-suppressive effects, potentially through anti-inflammatory or anti-proliferative pathways. For IMTs harboring ALK gene rearrangements, the use of ALK inhibitors such as crizotinib has produced notable therapeutic responses, including significant tumor regression and prolonged disease stabilization in both adult and pediatric patients. These agents are now recognized as promising treatment options for ALK-positive or surgically unresectable IMTs.

The earlier 2018 publication described only the initial presentation and short-term outcome of this patient and did not include long-term surveillance data or additional diagnostic information obtained during follow-up. In contrast, the present report offers extended 88-month postoperative findings, accompanied by more detailed multiphase imaging characteristics and comprehensive immunohistochemical profiling, allowing for a clearer understanding of the tumor’s biological behavior over time. In addition, this follow-up report incorporates updated pathological interpretation and reflects recent advances in the understanding and management of IMT. Contemporary literature up to 2025 highlights therapeutic considerations not discussed in the earlier Korean-language report, including the potential role of ALK inhibitors such as crizotinib, the selective use of systemic therapy in unresectable or recurrent disease, and evolving insights regarding recurrence risk stratification. These expanded diagnostic and therapeutic perspectives provide a more complete and current context for interpreting this case. The importance of this case is further underscored by several uncommon features occurring together: an adult-onset IMT arising from the second portion of the duodenum, an ALK- negative immunophenotype, and a positive resection margin without recurrence over 88 months of follow-up. This constellation is extremely rare in the published literature and offers meaningful insight into the long-term behavior of duodenal IMT, particularly in ALK-negative disease. By documenting extended clinical outcomes together with updated radiologic, pathologic, and therapeutic considerations, this follow-up report aims to provide additional insights that may supplement our previous publication.

In conclusion, duodenal IMT represents an exceptionally rare entity that is frequently difficult to distinguish preoperatively from other submucosal lesions of the gastrointestinal tract. Complete surgical excision remains the cornerstone of both diagnosis and treatment. Although IMT typically exhibits benign clinical behavior, the possibility of local recurrence underscores the need for careful and prolonged postoperative surveillance.

Supplementary Materials

Supplementary materials are available at the Korean Journal of Clinical Oncology website (http://www.kjco.org/).