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A rare case of rectal bleeding and Fusobacterium mortiferum sepsis due to solitary fibrous tumour originating from the mesentery
  1. Swaminathan Perinkulam Sathyanarayanan1,
  2. Khizar Hamid1,
  3. Kayla Hoerschgen2 and
  4. Tony Oliver1
  1. 1Department of Internal Medicine, University of South Dakota Sanford School of Medicine, Sioux Falls, South Dakota, USA
  2. 2Department of Pathology, University of South Dakota Sanford School of Medicine, Sioux Falls, South Dakota, USA
  1. Correspondence to Dr Swaminathan Perinkulam Sathyanarayanan; ashwin1694{at}gmail.com

Abstract

Solitary fibrous tumours (SFTs) are rare mesenchymal tumours that are mostly seen in the pleura. Lately, they have also been described in other locations. Recent discovery of the NAB2-STAT6 fusion gene which is specific for SFTs has led to an accurate diagnosis of SFTs. The occurrence of SFTs in the mesentery is very rarely reported in the literature. We report a case of a 63-year-old female who presented with abdominal pain, rectal bleeding and Fusobacterium bacteraemia, who was ultimately found to have a mesenteric SFT.

  • oncology
  • general surgery
  • gas/free gas

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Background

Solitary fibrous tumours (SFTs) are uncommon soft tissue spindle cell neoplasms of mesenchymal origin, accounting for less than 2% of all soft tissue tumours. They were originally described as pleural tumours by Klemperer and Rabin in 1931 and since then have posed a diagnostic and therapeutic dilemma. While the actual aetiology of these tumours remains unknown, they have mostly been diagnosed in adults of all ages, with highest incidence in the fifth and sixth decades.1

Case presentation

A 63-year-old Caucasian woman presented to the emergency department (ED) with sudden onset of high-grade fevers, chills, bright red blood per rectum and left lower quadrant abdominal pain. These symptoms were associated with abdominal bloating, nausea and severe lower back pain. She reported feeling well with normal bowel movement the preceding day. Her last colonoscopy which was done 3 years back was unremarkable except for sigmoid diverticulosis. Her medical and surgical history included hyperlipidaemia, hypertension, gastro-oesophageal reflux disease, anxiety, depression, right ductal carcinoma in situ (DCIS) status after lumpectomy and radiotherapy, hysterectomy, and laparoscopic bilateral salpingectomy and oophorectomy. She was not on any antiplatelets or anticoagulants. She had received the second dose of the Pfizer COVID-19 vaccine 4 days before presentation and felt fatigued after it. Vital signs in the ED showed blood pressure of 106/59 mm Hg, heart rate of 103 beats per minute, respiratory rate of 20 breaths per minute and arterial oxygen saturation of 94% on room air. Physical examination showed left lower quadrant abdominal fullness and tenderness.

Investigations

Leucocyte count was 1.7 × 109/L, haemoglobin was 123 g/L and platelet count was 149 × 109/L. Her sodium was 137 mEq/L; potassium, 3.5 mEq/L; chloride, 102 mEq/L; bicarbonate, 22 mEq/L; blood urea nitrogen, 14 mg/dL; creatinine, 0.99 mg/dL; alkaline phosphatase, 115 U/L; alanine transaminase, 32 U/L; and aspartate transaminase, 42 U/L. Lactic acid was elevated at 4.1 mmol/L, along with an elevated procalcitonin of 20.42 ng/mL. International normalised ratio was 1.02 and activated partial thromboplastin time was 30.9. Urine analysis was unremarkable; however, faecal occult blood test was positive. Influenza and SARS-CoV-2 were negative. Blood cultures were also drawn at the time of admission. CT of the abdomen with intravenous contrast revealed a 11.7×7.8×9.7 cm hypervascular pelvic mass with areas of necrosis and gas and extensive portal venous gas (figure 1). A 1.4 cm lesion in the left hepatic lobe was also noted, which was concerning for metastasis at that time. Chest X-ray was unremarkable. Carcinoembryonic antigen and cancer antigen 125 were 3.1 ng/mL (ref. 0–3 ng/mL) and 18 U/mL (ref. 0–35 U/mL), respectively.

Figure 1

Coronal CT of the abdomen/pelvis with intravenous contrast revealing a 11.7×7.8×9.7 cm hypervascular pelvic mass with areas of necrosis and gas (blue arrows) and portal venous gas (orange arrows).

Differential diagnosis

The differential diagnoses considered in her case include gastrointestinal tumours originating from the rectum/sigmoid colon, mesenteric soft tissue tumours, metastatic focus of her previously treated DCIS and pelvic mass causing sigmoid diverticulitis. Adnexal tumours were also taken into consideration, although she had a history of hysterectomy and bilateral salpingo-oophorectomy.

Treatment

A multidisciplinary approach was undertaken for her care with involvement from gastroenterology, oncology, infectious disease, general surgery and interventional radiology (IR). Initially, she was started on treatment with vancomycin, ceftriaxone and metronidazole for sepsis. Her blood cultures grew pansensitive Fusobacterium mortiferum, so the antibiotics were de-escalated to metronidazole. Repeat blood cultures showed no growth. Flexible sigmoidoscopy was done, which revealed an ulcerated non-obstructing large mass in the recto-sigmoid colon (figure 2). An oozing partially circumferential mass involving one-third of the lumen circumference and measuring 3 cm in length was noted. Biopsies revealed normal sigmoid colon tissue. Subsequently, plans for surgical resection were undertaken. Given the hypervascular nature of the mass, IR-guided microvascular plugging of the branches of middle colic artery originating from the superior mesenteric artery and microcoil embolisation of inferior mesenteric artery branches supplying the mass were done (figure 3). This was followed by exploratory laparotomy with lysis of adhesions, along with en bloc resection of the sigmoid colon in conjunction with the large mesenteric mass (figure 4). Stapled colorectal anastomosis and diverting loop ileostomy were made, and the mass was sent for pathology evaluation. Although the patient’s haemoglobin was stable at 12.3 g/dL on presentation, because of active rectal bleeding and surgical intervention, she developed acute blood loss anaemia and received 4 units of packed red blood cells during the hospital stay to maintain haemoglobin of >7 g/dL. The mesenteric mass was found to be a solitary fibrous tumour (figures 5 and 6) with high-risk aggressive behaviour forming a 15 cm mass. Resection margins were not involved (R0). Resected sigmoid colon revealed areas of focal ulceration adjacent to mesenteric mass along with 20 multiple benign regional lymph nodes.

Figure 2

Flexible sigmoidoscopy showing an ulcerated non-obstructing large mass in the recto-sigmoid colon.

Figure 3

Angiographic images of the blood supply of solitary fibrous tumour. (A) Superior mesenteric angiography showing branches of the middle colic artery supplying the mass. (B, C) Microvascular plugging of the middle colic artery branches supplying the mass. (D) Microcoil embolisation of the inferior mesenteric artery branch supplying the mass.

Figure 4

The surgical specimen that was resected.

Figure 5

Biopsy of the mesenteric mass showing solitary fibrous tumour with a mitotic index of 3/10 in high-power field. (A) Cellular tumour with large, staghorn vessels. (B) Cellular tumour with numerous small vessels and hyperchromatic, multinucleated cells. (C) Cells in a haphazard or patternless pattern configuration. (D) Tumour cells with irregular nuclei in a haphazard arrangement with multinucleated cells (H&E, original magnification: ×20 (A), ×100 (B), ×200 (C), ×400 (D)).

Figure 6

Vimentin (left) and STAT6 (right) expression in tumour cells (original magnification: ×40).

Outcome and follow-up

She was seen in the oncology clinic after discharge, and a staging CT scan of the chest, abdomen and pelvis was done. There was no evidence of metastatic disease. Her liver lesion had also shrunken in size and was thus deemed to be an infectious rather than a metastatic focus. Due to her R0 resection status, she was not a candidate for adjuvant chemotherapy.

Discussion

Although SFTs are most commonly reported in the pleura, they have also been reported in numerous other locations, common locations being meninges, subcutaneous tissue of the lower extremities, retroperitoneum and the orbit.2 Histologically, SFTs are composed of round-shaped to spindle-shaped cells with little cytoplasm surrounded by abundant eosinophilic bands of collagen arranged in storiform pattern. CD34 and Bcl-2 are the two most important and consistently positive immunohistochemical markers useful in the diagnosis of SFTs. NAB2-STAT6 fusion genes are specific for SFTs, and STAT-6 immunohistochemistry is recently being used as a surrogate for detecting the fusion gene. Other variably expressed markers include vimentin, CD99, BCL-2, nuclear beta-catenin and epithelial membrane antigen.3

SFTs originating in the mesentery are extremely rare with very few cases reported in the literature. Of the cases reported, most of them occur in the ileal mesentery.4 Most of the mesenteric SFTs reported in the literature presented with abdominal pain and abdominal fullness, while some were completely asymptomatic. By nature, SFTs are slow-growing tumours because of which they can remain asymptomatic until they reach a size big enough to cause abdominal swelling and compression of adjacent organs, resulting in abdominal pain.5–8 In our patient, the SFT had eroded into the sigmoid colon, resulting in rectal bleeding and acute blood loss anaemia. A small group of patients can present with a paraneoplastic entity called Doege-Potter Syndrome that is characterised by non-insulin-mediated hypoglycaemia due to the release of the prohormone big Insulin-like Growth Factor-2.9 10

One other unique feature of our patient was the F. mortiferum bacteraemia and the presence of portal venous gas. In fact, this is the first case of SFT ever to report a fusobacterial sepsis as a complication. The genus Fusobacterium is a gram-negative anaerobic bacillus that is a normal inhabitant of the oral cavity, female genital tract and the alimentary tract. Fusobacterium nucleatum and Fusobacterium necrophorum are the most frequent species isolated. F. mortiferum infections have been very rarely reported in the literature. If ever isolated, F. mortiferum is found in soft tissue infections above the waist and account for 2%–3% of all fusobacterial infections.11 12 In a case series study of fusobacterial infections, it was found that the mortality was the highest, ~50%, in F. mortiferum bacteraemia.12

Diagnosis of SFTs involves imaging and histopathological examination. It is universally agreed upon that surgical resection is the treatment of choice for SFTs. Given the hypervascular nature of the tumours, some patients might require embolisation prior to resection as in our patient.13

Learning points

  • Solitary fibrous tumours (SFTs) are rare spindle cell tumours commonly seen in the pleura. Their occurrence in mesentery is extremely rare.

  • Mesenteric SFTs presenting with rectal bleeding and sepsis are very uncommon.

  • Immunohistochemistry staining for STAT6 is very specific for SFTs.

  • Surgical resection is the treatment of choice. If they are hypervascular, embolisation prior to resection decreases the bleeding risk.

Ethics statements

Patient consent for publication

References

Footnotes

  • Contributors SPS was involved in the conception, drafting and revision of the manuscript. KhH was involved in the conception and drafting of the manuscript. KH was involved in image acquisition and drafting of the manuscript. TO was involved in drafting, editing and revising the manuscript. All authors approved the final version of the manuscript and agreed to be accountable for the accuracy of the manuscript.

  • Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

  • Competing interests None declared.

  • Provenance and peer review Not commissioned; externally peer reviewed.