Mesenteric Leiomyoma in Infancy.

A 10-year-old female presented with a palpable mass occupying the entire abdomen. Computerized tomography scan showed a large expansive lesion measuring 22 cm × 20 cm × 13 cm. The mass was resected and the diagnosis of leiomyoma was made from immunehistochemical findings. Mesenteric leiomyoma is an uncommon tumor among gastrointestinal stromal tumors.

INTRODUCTION

Stromal or mesenchymal neoplasms affecting the gastrointestinal (GI) tract account for only 1% of the primary GI tumors and are typically presented as subepithelial neoplasms. They are divided broadly into two groups.[1]

The most common group consists of neoplasms that are referred to as GI stromal tumors (GIST), predominantly found in middle-aged or older adults. They are most often located in the stomach (60%) and proximal small intestine (30%) but may occur in the omentum, mesentery, and peritoneum.[12]

A far less common group of mesenchymal GI tract neoplasms is comprised a spectrum of tumors that are identical to those that might arise in the soft tissues including lipomas, liposarcomas, leiomyomas, true leiomyosarcomas, desmoid tumors, schwannomas, and peripheral nerve sheath tumors.[1] Specifically, leiomyomas are very rare. In one series, they accounted for only 13 of the 1091 tumors originally classified as smooth muscle tumors of the small intestine (about 1%).[13]

Studies on GIST in the pediatric population are limited to case reports or small case series. An annual incidence rate of 0.02 per million in children below the age of 14 years has been calculated from data of the UK National Registry of Childhood Tumors or 1.4%–2.6% of all GISTs seen at large centers.[456]

Studies on non-GIST mesenchymal neoplasms affecting the GI in the pediatric population are lacking. Besides that, to the best of our knowledge, there have only been published two case of leiomyoma of mesentery in an infant in the literature.[78]

CASE REPORT

A 10-year-old Caucasian female patient was admitted to the General Hospital of Caxias do Sul with a 3-month history of diffuse abdominal pain worsening after eating. She also had food content emesis after meals and daily episodes of noninflammatory diarrhea. In the last 2 months began with abdominal distension. Abdominal ultrasonography showed extensive heterogeneous mass with cystic area in between measuring 25.0 cm × 17.6 cm × 8.0 cm compromising the entire abdominal cavity.

In the last month, the abdominal pain became worse in intensity. The patient had a weight loss of 6 kg in these 3 months. On physical examination, the patient was in regular general condition, pale, with a cystic consistency palpable mass occupying the entire abdomen.

Computerized tomography scan showed a large expansive lesion, heterogeneous, predominantly cystic, with gross septa that enhanced with the contrast, measuring 22 cm × 20 cm × 13 cm with a small amount of free fluid adjacent to the mass [Figure 1]. Magnetic Resonance of the abdomen showed large expansive mass with predominance of hyperintensity on T2 located next to the mesentery, measuring 22 cm × 18 cm × 10.4 cm with compression of adjacent structures without signs of infiltration. The initial differential diagnosis was neuroblastoma and lymphoma.

Figure 1

Computerized tomography scan showed a large expansive lesion, heterogeneous, predominantly cystic, with gross septa that enhanced with the contrast, measuring about 22 cm × 20 cm × 13 cm

Tumor resection was conducted the next day after admission [Figure 2]. Due to its proportions, midline laparotomy was indicated. The large mass was not adhered to the abdominal wall, its pedicle was located in the mesentery, and there were some adherences with the small intestine. After lysis of the adherences, the mass was enucleated without injuring any mesenteric vessel. The mesenteric origin of the mass suggested by the magnetic resonance was confirmed during the intraoperative period. The patient was discharged 5 days after the resection.

Figure 2

Resected tumor, measuring 26 cm × 18 cm × 6 cm and weighing 2645 g

The macroscopic examination showed cystic encapsulated brown-clear portion and plain tissue, measuring 26 cm × 18 cm × 6 cm and weighing 2645 g. The histopathological diagnosis was benign-appearing spindle cells with marked vascularization by delicate vessels and myxoid areas. No capsular involvement of the mass was evidenced. In immunehistochemical staining, the tumor stained positive for vimentine and smooth muscle actin (SMA), but negative for CD117, CD34, S-100 protein, and desmine. From these findings, the diagnosis of leiomyoma was made.

DISCUSSION

Classification of mesenchymal tumors of the GI tract has been the subject of controversy for many years, and several histological classification systems have been proposed.[124] A significant breakthrough was achieved with the identification of the near-universal expression of the CD117 antigen by GIST, in contrast to leiomyomas, true leiomyosarcomas, and other spindle-cell tumors of the GI tract, which were typically CD117-negative.[29]

The classic or usual GI tract leiomyoma has a similar morphologic appearance to leiomyomas in other organs. In the gut, they are usually small and well circumscribed. The tumors typically arise from the muscularis propria; growth may be intraluminal, extraluminal, or a combination with a dumb-bell shape. Leiomyomas can range in size from <0.5 cm (microleiomyomas) to as large as 30 cm.[12]

Microscopically, leiomyomas are formed of fascicles of benign-appearing spindle cells without nuclear atypia; mitoses are sparse or absent, and necrosis virtually never occurs.[1]

The differential diagnosis of a subepithelial tumor arising in the GI tract is broad, and a key distinguishing point is the near-universal expression of KIT (CD117) by GIST. Approximately 95% of GIST are CD117-positive, while 60%–70% are positive for CD34, 30%–40% percent are positive for SMA and 5% for S-100 protein. The immunohistochemical profile for leiomyomas is the negativity for CD117 and S-100 protein, while they are positive to SMA and desmin and 10%–15% are positive to CD34.[19] Besides that, neuroblastoma and lymphoma had been considered initially. Neuroblastomas can arise anywhere throughout the sympathetic nervous system, being the adrenal gland the most common primary site (40%), followed by abdominal site (25%). Non-Hodgkin lymphoma usually present with abdominal masses.[10]

The two other reported cases of leiomyomas in infancy describe the case of a 6-month-old male child with a palpable mass of 8.5 × 7.5 × 6.5 which was enucleated out entirely and the case of a 4-month-old male child with abdominal distension, bilious vomiting, and absolute constipation, which the ultrasonography revealed dilated gut loops with a hyperechoic mass in the ileal mesentery, being the tumor excised along with the adjoining gut.[78]

Our case report showed a 10-year-old female patient with the diagnosis of mesenteric leiomyoma, which is the third ever reported in the literature.

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Conflicts of interest

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