Inflammatory Myofibroblastic Tumor of Gut in Child: Case Report with Review

Goyal S and Singhal M

Published on: 2021-04-28

Abstract

Benign intestinal tumors are uncommon in children. An inflammatory myofibroblastic tumor (IMT) also called inflammatory pseudo tumor, is a benign spindle cell neoplasm masquerading as a malignant tumor with low malignant potential. Aetiology is unclear, although some authors suggest underlying trauma or distress result in reactive phenomenon. We describe an inflammatory myofibroblastic tumor (IMT) of the jejunum in an 8-year-old boy who presented with intestinal obstruction. During laparotomy, an annular mass around the jejunum was resected. A histological diagnosis of IMT was made as pathology examination revealed densely arranged bundles of spindle cells with diffuse infiltration of inflammatory cells and tumor involvement of the mucosa and serosa. A literature review for this rare entity emphasizes the importance of its benign nature. As it may be locally malignant and local recurrence can occur, these cases should have a long-term follow-up.

Keywords

Inflammatory myofibroblastic tumor; Inflammatory Pseudo tumor; Small Bowel

Introduction

In the WHO definition, inflammatory my fibroblastic tumor (IMT) is an uncommon spindle cell neoplasm with low malignant potential, and inflammatory fibro sarcoma and IMT are designated synonymously. It is full of mixed inflammatory cell infiltrate along with proliferative my fibroblasts. Symptoms and treatment vary and depend upon the site, multinodularity and proximity of the lesion to vital structures. Genetically speaking, approximately half of IMTs harbour clonal rearrangement of the anaplastic lymphoma kinase (ALK) gene, which encodes receptor tyrosine kinase. [1, 2] It has been understood that the inflammatory pseudo tumor is most likely a reactive process rather than a neoplastic proliferation. Despite the occurrence of a benign morphological pattern, some cases of IMT have been reported to have a malignant course. We report on a case of jejunal IMT presenting in an 8-year-old boy.

Case Report

An 8-year-old boy was admitted to the Department of Pediatric Surgery for intestinal obstruction. There was a history of intermittent vomiting and diarrhea for the last 4 months. The routine investigation was within normal limits. Ultrasound and CT Abdomen revealed small bowel thickening with narrowing along with small inflammatory soft tissue 13.4 x 8.4 mm mass in between small bowel loops in the right infraumbilical region (partial intestinal obstruction) (Figure. 1).

Figure 1: CT Abdomen Inst Obstrction.

During laparotomy, an annular mass surrounding the jejunum was discovered, and a jejunal resection was performed. The resected specimen consisted of a 10 cm long jejunal segment containing an intramural, circumferential and stenosing mass (Figure 2). The cut surface was homogeneous and of a firm consistency. The overlying mucosa and the attached mesentery were intact. Histopathology of the mass revealed an inflammatory myofibroblastic tumour (Figure 3). Immunohistochemistry was positive for smooth muscle acin. INC. and ALK1, DESMIN IHC focal positive, KI-67 positive 6-8%, negative for CD117, C-KIT, S-100P, and PAN CYTOKERATIN IHC.

Figure2: Mass during laparotomy.

Figure 3: Resected specimen of IMT.

Discussion

Extra-pulmonary IMT can occur anywhere in the body, and the majority of cases have been reported in childhood and early adulthood.[3] It was first reported in 1937 as a lung tumour. Sites of extra pulmonary IMT may include the upper respiratory tract, mesentery/omentum, genitourinary tract, gastrointestinal tract, retroperitoneum, pelvis, head and neck, trunk and extremities. Several terms, such as a pseudo inflammatory tumour, inflammatory fibroid tumour, eosinophilic granuloma, plasma cell granuloma, xanthomatous pseudotumor, inflammatory myofibrohistiocytic proliferation and inflammatory fibrosarcoma have been used to describe this lesion [1]. OMMH has many similar morphological features with IMT, and it may represent a variant of IMT.[4].In most cases, IMT of the small intestine was located in the small bowel's mesentery, as in our case. Due to variable terminology, the number of gastrointestinal IMT cases reported in children in literature is not accurate still are tabulated in Table-1 [5].

Table 1: Variable terminology, the number of gastrointestinal IMT cases reported in children in literature.

Report	year	Gender	Age (y)	onset	Size (cm)	Location	preoperative diagnosis		ALK-1	follow up	recurrence	Complication
Ciftici [6]	1998	M	9	Inst. Obst.		Mesentery Mass terminal ileum, cecum, and ascending colon	Int. Obst.	NR		NR	-	-
Cviko [7]	1999	M	7	abdominal pain	?15		a malignant neoplasm	NR		2y	–	-
Demirkan [8]	2001	F	2	vomiting and diarrhoea	2.0 × 1.5	3cm long jejunal segment	small intestinal obstruction	NR		NR	NR	NR
DiFiore [9]	2002	F	3	abdominal pain, nonmobile, palpablemass	11x6x9	the antimesenteric border of a small bowel loop in the distal jejunum	NR	NR		2y	–	–
Zuccarello [10]	2006	M	4.5	abdominal pain, constipation, and vomiting	2.0 × 1.7	annular mass around the ileum	intussusception and obstruction	NR		3y	after 3month	–
Yimyaem [11]	2010	M	0 (2months)	abdominal distension and vomiting	2.0 × 3.0	surrounding the terminal ileum	small bowel obstruction	negative		18m	–	–
Amouei [12]	2016	M	5	palpable abdominal mass	10x8	ileum 20 cm away from ileocecal valve	myofibrob-lastic tumour or neuroblastoma	NR		NR	NR	NR
Oeconomopoulou [4]	2016	M	6	acute abdominal pain	6x2	ileum 8 cm away from the ileocecal valve	acute appendicitis or Meckel's diverticulum	negative		2y	–	–
Yu [13]	2017	F	15	abdominal pain, nausea, and vomiting	11.5 × 9 × 8	NR	soft tissue mass	positive		3m	–	–
Rina [5]	2020	F	1.5	abdominal pain, nausea, and vomiting	2.5 × 3.0	ileum 43 cm away from the ileocecal valve	intussusception	positive		6m	–	–

The etiological factors responsible for IMT are unclear. IMT may be due to reactive response to previous injury, inflammation, or distress. IMT may be an immunological response to an infectious or noninfectious agent. Campylobacter jejuni, Epstein-Barr virus (EBV), and Escherichia coli are linked with IMT. The trauma, steroid use, abdominal surgery, and genetic factors have been associated, but the pathogenesis of IMT is unclear. Several reports have focused on the potential relationship between the EBV and IMT. In the present case, there was no EBV positivity. [4]. The clinical presentation of IMT varies According to the location of the tumour. At the intestinal location, the onset may be insidious or rapid and may be accompanied by weight loss, malaise, a mass, bleeding, and vomiting or bowel obstruction. [14]. Childhood IMT cases with an intramural location of the tumour have interestingly presented with diarrhea and intestinal obstruction, as in the present case. Microscopically, a diversity of patterns can be seen in IMT. Inflammatory myofibroblastic tumours are characterized by a mix of inflammatory cells, e.g. plasma cells, lymphocytes and eosinophils, and bland spindle cells without nuclear atypia. These tumours may have necrosis, haemorrhage, focal calcification and mitotic activity. [15] Most lesions are composed of a compact proliferation of spindle-shaped cells arranged in a storiform or fascicular growth pattern as in our case. The mitotic rate is low. Immunohistochemistry is important in confirming the diagnosis as mesenchymal cells are immunoreactive for vimentin, desmin, SMA, and S100 protein and do not express CD34 [6]. Up to 71 % are positive for ALK-1; this immunophenotypic feature is more common in younger males as in our case. It is associated with a high recurrence rate [4]. The differential diagnosis of IMT is not easy even at a microscopic level, and immunehistochemical analysis helps to differentiate IMTs from other tumours, such as gastrointestinal stromal tumours, leiomyosarcomas, and inflammatory malignant fibrous histiocytomas [7], calcifying fibrous pseudotumour, inflammatory fibroid tumour, nodular fasciitis. The inflammatory myofibroblastic tumor cannot be distinguished clinically from highly malignant neoplasms and some other conditions, as radiologically, it is difficult to differentiate from a malignant tumour. IMTs usually have a benign course, and recurrence or distant metastasis is rare. The incidence of local recurrence has been 15–37 % when an IMT is located in the mesentery or the retroperitoneum. Complete surgical resection is the treatment of choice for IMT [4]. A long term clinical and radiological follow up is mandatory. Biological behavior mostly depends on the size, mitotic activity, tumour cell necrosis and resection line positivity. ALK translocation also gives a remedial choice because ALK inhibitors like crizotinib and alectinib can stop uncontrolled cell proliferation. ALK inhibitor treatment is recommended in surgically incurable, metastatic and recurrent cases [16, 17, 18].