|Year : 2019 | Volume
| Issue : 4 | Page : 193-196
Solitary fibrous tumor of rectus sheath
Po-Hsien Wu1, Huai-En Lu2
1 Department of Surgery, Division of Colon and Rectal Surgery, Tri-Service General Hospital, National Defense Medical Center, Taipei, Taiwan
2 Department of Surgery, Song Shan Branch, Tri-Service General Hospital, National Defense Medical Center, Taipei, Taiwan
|Date of Submission||04-Nov-2018|
|Date of Decision||24-Jan-2019|
|Date of Acceptance||26-Feb-2019|
|Date of Web Publication||13-Aug-2019|
Dr. Po-Hsien Wu
Department of Surgery, Division of Colorectal Surgery, Tri-Service General Hospital, National Defense Medical Center, 325 Chenggong Road, Section 2, Taipei 114
Source of Support: None, Conflict of Interest: None
Solitary fibrous tumor (SFT) is a rare tumor with incidence <2% in all soft tissue tumors. About 30% of SFTs arise in thoracic cavity, 30% arise from the intra-abdominal cavity, and another 20% occur in head and neck. We presented a case with a painless, slow-growing intra-abdominal tumor for more than a decade. Physical examinations, blood test, and image studies provide little clues preoperatively. Definite diagnosis relies on pathological confirmation. Currently, there are numerous immunohistochemistry tools to facilitate making diagnosis correctly.
Keywords: Solitary fibrous tumor, extrathoracic, clinicopathological features, surgery, tumor of rectus sheath
|How to cite this article:|
Wu PH, Lu HE. Solitary fibrous tumor of rectus sheath. J Med Sci 2019;39:193-6
| Introduction|| |
Solitary fibrous tumors (SFTs) are uncommon mesenchymal neoplasms first described in 1931 and account <2% of all soft tissue tumors. Initially, SFTs are thought to be intrathoracic tumors. Moreover, recent reports unveil that SFTs occur almost everywhere of human body including the intra-abdominal cavity, central nervous system, head and neck, bone, salivary gland, thyroid, liver, and prostate. SFTs of the abdominal wall are extremely uncommon and there are only 16 cases had been reported till date. SFTs are most commonly diagnosed from fifth to seventh decades, and the mean age is 58 years. There is no sex predilection. In this report, we describe a new case of SFT that originates from rectus sheath and discuss the clinical symptoms, signs, image findings, and pathological characteristics.
| Case Report|| |
A 42-year-old female presented to our surgery department because of a slow-growing abdominal mass for the past 10 years. Her family and medical history were unremarkable, and she had no history of previous abdominal surgery. There was no nausea, vomiting, involuntary body weight loss, and pain. On physical examination, a firm, movable, painless mass in the left-sided abdomen on deep palpation. Laboratory tests including metabolic panels, tumor markers, and C-reactive protein were within normal range. Computed tomography (CT) with intravenous contrast showed a well-circumscribed mass, measuring 6 cm × 4.6 cm × 6.7 cm, with heterogeneous enhancement [Figure 1] attached to rectus sheath. Magnetic resonance (MR) imaging disclosed a bright high-signal tumor mass after gadolinium administration [Figure 2].
|Figure 1: Abdominal computed tomography showing a well-circumscribed tumor mass attached to the rectus muscle and sheath. Axial (a) and coronal (b) contrast-enhanced computed tomography scans showing a heterogeneous enhancing mass (arrows in a) that displaces small bowel and also serpentine vessels near the mass is seen (arrow in b)|
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|Figure 2: Axial fat-saturated T1-weighted magnetic resonance image revealed a mildly hyperintense lobulated mass (arrows in a) and heterogeneous high signal intensity after gadolinium administration (arrowheads in b)|
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At laparotomy, a large, encapsulated tumor adhered to rectus sheath was found. The tumor did not invade to adjacent visceral organs. Grossly, the tumor was well capsulated, soft consistence, and covered with multiple vessels [Figure 3]. The size was about 7 cm × 5 cm × 4 cm. Histologically, the sections showed proliferative spindle cells separated by normal-looking endothelial cells lining small vessels and focally staghorn configuration. Furthermore, the neoplasm had uncommon mitotic activity (2/10 hpf), and there was no necrosis [Figure 4] in fields. Immunohistochemically, the tumor was positive for CD34 [Figure 5] and STAT6 [Figure 6] but negative for S100 protein, smooth muscle actin, and DOG1. Hence, the histological feature was compatible with benign SFT.
|Figure 3: Intraoperative findings: A 7 cm × 5 cm × 4 cm encapsulated mass with multiple feeding vessels on tumor surface|
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|Figure 4: Histological findings (H and E) showing alternating hypocellular and hypercellular areas and several prominent staghorn capillaries|
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|Figure 5: Immunohistochemical features of the neoplasm: Diffusely immunoreactive to CD34|
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|Figure 6: Immunohistochemical features of the neoplasm: Strong nuclear STAT6 antibody reactivity whereas vascular endothelial cells are negative|
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The postoperative course was uneventful, and she was discharged 5 days after the surgery.
| Discussion|| |
Clinical symptoms and signs of SFTs vary based on the location and size of the tumor. A palpable, nontender, slow-growing mass is the most common presentation. Large tumor may cause gastrointestinal symptoms such as nausea, vomiting, and constipation.
Imaging modalities such as CT and MR could help to diagnose SFT. On CT, SFT shows a well-circumscribed and hypervascular mass with external compression of adjacent organs. Calcification is rare in SFT. Central hypodense indicates tumor necrosis or cystic change. In our case, the CT images are compatible with these image features. On MR, SFT usually presents with intermediate intensity on T1-weighted image and heterogenous hypointense on T2-weighted image, which is related to hypercellularity or collagen. Intense enhancement is seen after the administration of gadolinium contrast material., However, this case demonstrates a high signal intensity on T1-weighted image before administration of gadolinium and is less common.
Recognizing typical morphology and specific immunohistochemical findings are keys to diagnose SFT on histological examination. Grossly, the tumor usually presents a sharply circumscribed mass with smooth, bosselated, or lobulated external surface. Microscopically, classical morphological appearance including “patternless pattern” caused by variable spindled cells arrayed in the stroma. Furthermore, prominent and anastomosing “staghorn” capillaries are also observed., Enzinger and Smith published criteria to identify malignant SFT including ≥4 mitotic figures/10 hpf, larger size, high cellularity, nuclear pleomorphism, and presence of hemorrhage or necrosis. Since the histologic characteristics are relatively nonspecific to diagnose SFT, immunohistochemistry plays a vital role to help diagnose and differentiate from other spindle cell tumors. Conventional markers of SFT including diffuse strong positive of CD34, moderately positive of BcL-2 and CD99, and absence of S100, actin, and DOG1., Furthermore, newer immunohistochemistry STAT6 test to detect NAB2-STAT6 fusion gene had been used to differentiate SFT from other mimics and reached significant high sensitivity and specificity., In our case, both histologic characteristics and immunohistochemistry tests showed classic SFT appearance.
Differential diagnosis of tumor arising from rectus sheath including desmoid tumor, hematoma, and infection. The most common tumor arising from rectus sheath is desmoid tumor. Other etiologies including hematoma and infection processes such as scar abscess or diverticulitis. Clinical presentations and image characteristics of desmoid tumor on CT and MR mimic SFTs. Therefore, surgical pathology is the cornerstone of making diagnosis. Unlike SFTs, desmoid tumor shows reactive actin and nonreactive CD34 on immunohistochemistry tests. Hematoma of rectus sheath cannot be accurately diagnosed solely based on symptoms and signs (such as anorexia, nausea, fever, and tachycardia) due to lack of specificity. Hence, ultrasound or CT plays a role of making diagnosis and furthermore preventing unnecessary surgery. Most hematomas could be managed conservatively. The third common mass of rectus sheath is infection. When a mass accompanied with fever, tenderness and leukocytosis raise the suspicion of infection. Numerous infectious processes such as scar abscess, diverticulitis, and Crohn's disease had been reported to cause rectus sheath mass. Some will be resolved with antibiotics alone and others may need surgical or percutaneous drainage.
Surgical resection with curative intent is the mainstay therapy for SFT. Adjuvant radiation therapy and chemotherapy are not recommended contemporarily because of the lack of validating data to support these treatments. Newer molecularly target agent therapy is still under-investigated.
| Conclusion|| |
We present a rare SFT of rectus sheath in a middle-aged woman. Preoperative diagnosis of the disease is difficult because of the nonspecific findings on physical examinations and imaging studies. Correct diagnosis of the tumor needs surgical en bloc resection and histopathological confirmation.
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6]