Solitary fibrous tumour of caecum wall: an unlikely cause of low gastrointestinal haemorrhage

Abstract

Solitary fibrous tumour (SFT), previously denominated as haemangiopericytoma, is a rare, spindle cell neoplasm that was first described in the thoracic pleura. It is now known that this tumour may develop from almost any anatomic location. We report a case of SFT, in a 65-year-old man, which was located in the muscularis propria layer of the caecum with involvement of the serosa and the ileocecal appendix, location never described in the literature, and with an uncommon clinical presentation of hematochezia. A radical right hemicolectomy was performed, and the patient was asymptomatic without evidence of metastasis or relapse after 6 months of follow-up.

Background

Solitary fibrous tumour (SFT) constitutes a heterogeneous group of rare spindle-cell tumours that include benign and malignant neoplasms.¹ This type of tumour has several histological features in common with haemangiopericytoma, which is a vascular sarcomatous tumour described in 1942 by Stout and Murray;² however the term ‘solitary fibrous tumour’ was first used in 1931 by Klemperer and Rabin to describe the same type of tumour.³ In 2002, the WHO has defined the term ‘fibrous tumour’ covering several mesenchymal tumours, including haemangiopericytoma.⁴

It is a rare soft tissue neoplasm, with an incidence of about 0.2/100 000/years.⁵

Case presentation

A 65-year-old man, with no relevant pathological history, went to the emergency department with abdominal pain and hematochezia with 24 hours of evolution. On physical examination, he presented abdominal distension, discomfort to abdominal palpation, with a hard, movable and non-pulsatile mass on the right iliac fossa. At the proctological examination, there were no visible haemorrhoids or fissures, sphincter normotonic and without palpable masses to the rectal touch, gloved finger with traces of hematochezia.

Investigations

Blood samples revealed normocytic and normochromic anaemia, haemoglobin of 10.3 g/L (reference value 13.0–18.0 g/L), and C reactive protein 6.4 mg/dL (value 0–0.5 mg/dL).

The orthostatism X-ray abdomen did not reveal hydroaeric levels or gas under the diaphragm.

The patient performed an abdomionopelvic ultrasound, which revealed irregular thickening of the caecum in the right iliac fossa, with a heterogeneous expansive lesion with 9×5×6 cm, apparently associated with intussusception.

The colonoscopy showed, in the ascending colon/caecum, a large necrotic mass in relation to the intussusception described in the previous imaging study.

Differential diagnosis

The first hypothesis of diagnosis was intestinal invagination, which, although rare, the complementary diagnostic tests performed pointed to this diagnosis. If intussusception has been confirmed, the most likely cause in the adult would be neoplasia.

The other hypotheses would be colon neoplasia without invagination, such as adenocarcinoma or GIST (gastrointestinal stromal tumour).

Treatment

The patient underwent an exploratory laparotomy, and an inflammatory/tumour mass was observed intraoperatively at the level of the caecum with about 10 cm of greater axis. He was then submitted to radical right hemicolectomy (figure 1) with primary ileocolic anastomosis.

Figure 1.

Resected specimen of right hemicolectomy, with the caecum swollen and the appendix is not seen since it was invaginated.

The postoperative period was uneventful, being discharged on the seventh postoperative day.

Histopathological examination of the resected segment demonstrated a spindle cell tumour, with 6×8 cm, centred mainly in the muscularis propria layer of the caecum with involvement of the serosa and the ileocecal appendix, without significative atypia, with prominent vascularity, associated with invagination and inflammatory aspects of the caecum and appendiceal mucosa (figure 2). No lymphatic, venous or perineural invasion is observed. Absence of necrosis and low mitotic index (2 mitoses per 10 high-power field) were noted, and sixteen lymph nodes were isolated.

Figure 2.

Solitary fibrous tumour. A spindle cell tumour centred mainly in the outer layers of the colon wall, with prominent vascularity. Spindle cells with plump nuclei without significative atypia.

In the immunohistochemical examination, the spindle cells were negative for muscle cell markers, GIST markers (C-KIT and DOG1) and neural markers. CD34 and CD31 showed the rich vascular network but were mainly negative in tumour cells. STAT6 was diffusely positive (figure 3).

Figure 3.

Solitary fibrous tumour. The spindle cells were negative for muscle cell markers, GIST markers and neural markers. CD34 and CD31 showed the rich vascular network but were mainly negative in tumour cells. STAT6 was diffusely positive. GIST, gastrointestinal stromal tumour.

Outcome and follow-up

After a clinical case discussion in a multidisciplinary group consultation, it was decided to perform a complementary study with thoracoabdominal CT to exclude metastatic disease. No lesions compatible with local recurrence, or evidence of distant metastasis, were observed in CT scan.

It was then decided to maintain clinical and imaging surveillance.

At 6 months of patient follow-up, he remains clinically asymptomatic and without any evidence of relapse or distant metastasis.

Discussion

SFT is a rare tumour, representing only about 1%–2% of all soft tissue tumours.⁶

The WHO’s classification system of soft tissue tumours categorises SFTs as neoplasms with intermediate biological potential, which presents a relatively indolent course and have a low risk of metastasis.⁷

Initial studies on SFTs reported that these neoplasms were originated exclusively from the thoracic pleura.^{7 8} More recent studies have shown SFTs are ubiquitous neoplasms, which may arise from almost any anatomic location.^{7 9–16}

The behaviour of extrapleural SFTs is unpredictable. Roughly 10%–15% of them show malignant behaviour, in the form of recurrent and⁄or metastatic disease, and thus long-term follow-up is mandatory.^{4 8 9}

Criteria of malignancy for SFT include disseminated disease at presentation, large tumour size (>50 mm), infiltrative margins, high cellularity, nuclear pleomorphism, areas of tumour necrosis and an increased mitotic index (>4 mitoses per 10 HPF).^{8 9}

The most characteristic immunohistochemical finding in SFT is CD34 expression. Although in some cases the histological diagnosis of SFT may be relatively simple, some tumours may mimic other benign mesenchymal tumours or sarcomas, in addition to a subset of SFTs that do not have CD34 expression,¹⁷ as in the reported case. Nuclear expression of STAT6 is found in almost all cases of SFT and very rarely in other soft tissue neoplasms. STAT6 is an extremely sensitive and specific immunohistochemical marker for SFT and may be useful to distinguish this type of tumour from histological mimics.¹⁷

Adequacy of resection margins after surgical excision of SFTs is a strong prognostic indicator of local disease recurrence and long-term survival.^{7 15 16}

Currently, there is little evidence that adjuvant chemotherapy and radiation therapy following complete surgical resection is beneficial and thus they are not routinely performed.¹⁵

In conclusion, we report a clinical case of a SFT of the colon, whose location is extremely rare. Only a few cases of SFT of the intestinal mesentery were found in the literature and in only one case, it was located in the wall of the colon sigmoid (serosa).¹²

Learning points.

• Solitary fibrous tumours (SFTs) are rare neoplasms that can occur at all anatomic sites.

• About 85%–90% have benign behaviour.

• Complete surgical excision is gold standard of treatment, but in cases of malignant SFT or when complete excision is not possible, chemotherapy and/or radiotherapy may be considered.

• Given the rarity of these tumours and the uncertainty of their prognosis, a tight and prolonged follow-up should be maintained.