PET-positive suture granuloma of abdominal wall 56 years post-appendicectomy mimicking recurrence of lymphoma

Abstract

We present a unique case of a positron emission tomography (PET)-positive suture granuloma deep to an appendicectomy abdominal wall scar from 56 years prior in a patient with treated lymphoma. The lesion was first detected 8 years ago on a PET scan for new diagnosis of follicular lymphoma, with stable appearances 6 and 7 years later at follow-up. Ultrasound-guided biopsy and flow cytometry of the specimen could not exclude an untreated or recurrent lymphoma; thus, the patient underwent resection of the right iliac fossa abdominal wall lesion. Histopathology results noted granulomatous inflammation surrounding foreign material. The patient had an uneventful postoperative recovery and was discharged from surgical services. In this paper, we review the current literature and discuss the dilemma involved in the diagnosis and management of suture granulomas.

Background

Foreign bodies can induce an immune reaction of macrophages that develops into a nodular lesion containing granulation tissue. When surgical sutures are involved, these benign tumours are called suture granulomas.^{1 2} Fluorodeoxyglucose (FDG)-avid suture granulomas from tumour resection sites may resemble new masses and raise concerns of relapse, warranting further exploration and resection.²

Suture granulomas may develop months to years postoperatively; however, the presence and occurrence of suture granulomas over 50 years post-surgery are unreported. To our knowledge, we also describe the first incidence of suture granuloma in the context of a haematological cancer. This further complicates diagnosis as fine-needle aspiration and/or core biopsy of the lesion would likely show proliferation of lymphocytes and raise suspicion of malignancy. While suture granulomas are predominantly picked up due to localising symptoms, in our case, the patient remained asymptomatic. This case describes a uniquely stable and unresolving suture granuloma that remained FDG avid when monitored over a 7-year period, which is in contrast to most cases which are either dealt with at first instance, or spontaneously resolve with conservative management.

Case presentation

A woman in her 70s was initially referred 8 years ago by her general practitioner for investigation of a new right breast lump with associated mastalgia. The breast lump was biopsied, revealing grade 2 follicular lymphoma. Excisional biopsy confirmed the diagnosis, and staging CT demonstrated multiple lung lesions and mediastinal infiltration. Haematological testing was negative for bone marrow infiltration.

At time of diagnosis, the patient’s medical history included peptic ulcer disease, osteoarthritis of the back, dyslipidaemia and depression. Her surgical history included open appendicectomy, tonsillectomy and right carpal tunnel release. She had no history of malignancy or airway disease and was a non-smoker who abstained from alcohol. Her body mass index was 34 kg/m². Her family history was significant for an uncle with lymphoma of unknown type, diagnosed in his 40s.

The patient was referred for oncological review. She reported a persistent chronic dry cough but was otherwise asymptomatic, without loss of weight or other constitutional (B-type) symptoms. She underwent further investigations including positron emission tomography (PET) scan, flow cytometry and haematological testing which revealed stage 4A grade 2 follicular lymphoma with significant mediastinal lymphadenopathy and scattered coeliac axis and pelvic nodal deposits. Additionally, multiple nodular opacities were noted throughout both lungs. It is at this time that an FDG-avid abnormality was noted anterior to abdominal wall muscle near its insertion into the right superior iliac crest (figure 1A).

Figure 1.

Positron emission tomography scan coronal and axial views; comparison of (A) and (C) initial with (B) and (D) most recent imaging demonstrating persistent fluorodeoxyglucose-avid lesion in the right iliac fossa abdominal wall (circled in red).

Following discussion at cancer care multidisciplinary meeting (MDM), the patient was enrolled in the ASSIST-FL trial, a trial for patients with previously untreated advanced stage follicular lymphoma. She was treated with the rituximab, cyclophosphamide, vincristine sulfate and prednisone chemotherapy regimen and underwent eight cycles of primary, then maintenance chemotherapy, which concluded 2 years after commencement. This was followed by 2 years of maintenance rituximab during which she developed peripheral neuropathy of the hands, palms and lips, shortness of breath on exertion and intermittent hot flushes. These symptoms were in addition to longstanding and persistent right breast mastalgia. The patient received extensive multidisciplinary care from respiratory, haematology, oncology and breast teams to monitor and manage these symptoms.

PET imaging 2 years ago displayed an FDG-avid enlarging right upper lobe (RUL) lung nodule in addition to prominent bilateral hilar and mediastinal lymph node avidity. Otherwise, the scan demonstrated stable activity since the initial scan, including the soft tissue lesion in the right iliac fossa (RIF). The lung nodule was biopsied and found to be adenocarcinoma in situ (T1N0), requiring right middle lobectomy and mediastinal lymph node dissection.

Repeat imaging of the RIF lesion last year continued to show stable size and FDG avidity. However, considering the recent development of new lung cancer, discussion at MDM determined that further investigation of the RIF lesion was warranted.

Investigations

On retrospective review of the initial staging CT, a soft tissue lesion measuring 11.1×17.3 mm involving the RIF can be seen. However, preliminary staging PET scan was first to officially comment on the moderately intense FDG-avid soft tissue density immediately anterior to the abdominal wall muscle at its insertion into the right iliac crest (figure 1A). The lesion had a maximum standardised uptake value of 8.31 and remained stable in size and appearance across a period of 7 years as evident from its appearance on PET scans in later years (figure 1B).

The RIF lesion was initially investigated with an ultrasound (US) which demonstrated a 44×12×22 mm lobulated, hypoechoic, non-vascular area in the right lower anterior abdominal wall deep subcutaneous fat amenable to biopsy. Subsequent US-guided core biopsy showed fibroadipose tissue with focal fibrosis and patchy aggregates of foamy macrophages and multinucleated giant cells, without evidence of lymphoma or other malignancies. However, flow cytometry described abnormal populations of cells of follicular origin and naturally raised the possibility of secondary lymphoma. It is at this time the patient was referred for surgical review for consideration of surgical excision of the lesion.

On review in surgical outpatient clinic this year, the lesion appeared to underlie a previous open appendectomy scar from 56 years ago. It was non-palpable, with minor focal tenderness over the RIF. The patient was booked and consented for surgical excision of the lesion.

Histopathology of the excised RIF lesion revealed an ill-defined 12 mm firm grey lesion consisting of non-necrotising, granulomatous inflammation surrounding some polarisable foreign material, without evidence of dysplasia or malignancy (figure 2). This foreign body was thought to be suture material left from prior appendicectomy—given that the lesion was deep to the site of the previous surgical scar and likely related to a suture repair of the external oblique incision.

Figure 2.

Histopathology of the abdominal wall lesion. (A) Specimen in H&E stain—fibrous and adipose tissue containing well-formed granulomas (arrow) showing foreign body-type giant cells and associated epithelioid histiocytes. (B) In association with some of the granulomas, polarisable foreign materials (arrows) are identified.

Differential diagnosis

Initially identified during the patient’s staging PET scan 8 years ago, given its FDG avidity, the RIF lesion was thought to either represent extranodal deposition of primary lymphoma or be of reactive inflammatory origin.

Findings of an enlarging RUL lung mass 2 years ago, later found to be adenocarcinoma in situ, naturally raised the possibility of a unifying diagnosis of sarcoidosis to account for the granulomatous lung lesions and RIF lesion.

US findings and core biopsy histology of the RIF lesion appeared benign; however, flow cytometry demonstrated clonal expansion of follicular origin cells which naturally raised concerns of secondary deposition of the primary lymphoma.

Treatment

Given the inconclusive findings from histopathology and flow cytometry, the patient underwent excisional biopsy to rule out malignancy. This procedure was a day-case completed under general anaesthetic with intraoperative findings revealing a contained lesion surrounded by gritty scar tissue which was suspicious for granuloma. No obvious nodal disease was evident.

Outcome and follow-up

Following surgical excision last year, the patient was reviewed 4 weeks later in surgical outpatient clinic and had recovered uneventfully. The histopathological findings were discussed at the MDM which concluded that the RIF lesion most likely a benign suture granuloma secondary to previous open appendicectomy. Given suture material remains, the consensus was that further PET imaging of the region will likely remain positive and that patient reassurance is the best course of action.

The patient was discharged from surgical services and returned to routine follow-up with oncology, respiratory, thoracic and breast clinics for ongoing symptom management.

Discussion

Suture granulomas can evolve months to years after surgery. Yoshioka et al reported development as early as 9 weeks post-resection for oral squamous cell carcinoma, while Khoo et al and Zein et al both reported delayed occurrences 37 years later in the eye.^2–4 In contrast, our patient had a suture granuloma at the site of her open appendectomy performed 56 years earlier. Given that the lesion was FDG avid on the first PET scan, it remains unknown as to when the granuloma had initially developed. Silk sutures are typical for immune reactivity and formation of suture granulomas, whereas absorbable materials are infrequently involved. Formation of suture granulomas has also been implicated in surgical sites shortly after radiation therapy.^{1 2} Suture granulomas can potentially form at any previous surgical site, with published locations ranging from the eye to scrotum.^3–5

Deep and non-palpable suture granulomas may be complicated by pain and/or abscess formation, whereas subcutaneous masses may be palpable underneath suture lines.^{2 5–8} Depending on location, further complications such as hydronephrosis (low anterior resection for rectal cancer), dysphagia (laparoscopic Heller myotomy and Dor fundoplication for type II achalasia), and patellar tendon necrosis and rupture (relapse post-initial repair) have also been documented.^9–11 Sizes range from 5 mm nodules along the neck to 9 cm within the abdominal wall.^{2 7}

Suture granulomas are rarely indolent and usually picked up following investigation of symptoms rather than incidentally on postoperative CT and PET imaging following cancer resection, as with this patient. Kikuchi et al described similar exceptions involving two cases of suture granulomas with FDG activity which were found 3 years after primary tumour resection during routine repeat PET scans.⁸ Okazaki et al treated two patients with raised carcinoembryonic antigen, prompting CT and subsequently PET scan that resulted in FDG-avid lesions approximately 6 months following pulmonary segmentectomy for primary lung cancers.¹²

Suture granulomas are difficult pathologies to diagnose preoperatively, especially within a body cavity compared with skin surface.¹ Imaging modalities range from US with imaging-guided biopsy, CT, MRI and PET scan to further evaluate the lesion and rule out malignancy.² However, suture granulomas show false-positive FDG activity during PET scan, likely due to chronic inflammation with presence of granulation tissue.² Interestingly, our FDG-avid lesion came from a non-tumour site (open appendicectomy) in a patient with primary lymphoma diagnosed from a breast excisional biopsy, and a subsequent lung adenocarcinoma with right middle lobectomy and lymph node dissection. The tumour resection sites did not form complications such as suture granuloma during the period of follow-up. This is likely due to use of different sutures from the open appendicectomy that the patient underwent. Therefore, non-absorbing suture materials, particularly silk, with their higher likelihood of forming inflammatory responses and suture granulomas, should be avoided during cancer resections.

Following review of the history and evolution of surgical sutures, the most likely suture material used to close the abdominal wall following her appendicectomy would have been either absorbable catgut or non-absorbable silk. Charles McBurney described the closure of muscle layers in his pioneering ‘McBurney’s incision’, for open appendicectomy technique using catgut sutures in 1894.¹³ Mersutures’ eyeless needles with single-strand threads debuted in the 1920s, yet catgut continued as the staple absorbable suture through the 1930s, with silk and cotton as the choice for non-absorbable sutures.^14–16 More contemporary materials used in current practice were only released after the mid-1960s by Ethicon, namely polypropylene Prolene (1969), Vicryl (1974), polydioxanone (PDS II) (1982) and Monocryl (1993) sutures.¹⁴

Biopsies, while useful diagnostically when lesions are accessible, have been known to yield false-positive results. Kikuchi et al provide an example of this reporting a case of a patient with FDG accumulation after radical surgery for oropharyngeal squamous cell carcinoma.⁸ Fine-needle aspiration cytology suggested tumour recurrence but this was disproved via histopathological diagnosis of suture granuloma from excisional biopsy.⁸ In our case, it was difficult to rule out lymphoma from US-guided biopsy due to expression of abnormal cluster of differentiation cells on flow cytometry that may be present in suture granulomas as well as different forms of lymphoma.

In conclusion, we present a case of an FDG-positive suture granuloma present 56 years following the original operation. The lesion in our patient was also unique as it was first noted 8 years ago and remained stable in appearance, and is the first known case to be persistently FDG avid with follow-up imaging for 7 years.

Patient’s perspective.

At first I didn’t really notice the lump in my lower tummy - well because I had multiple other health concerns, mainly my bad lungs and I was coughing a lot. When the doctor saw it light up in one of the scans and said I needed more testing, I was worried it could be cancer and mean more rounds of chemotherapy. In the end the doctors talked about cutting it out and I agreed, I just wanted it out if it could be cancer. The operation was quick and I could go home on the same day. I was quite relieved when the doctors said it wasn’t cancer but it is quite astounding that this developed from an operation I had so long ago. I hope that this research paper helps other doctors learn from my experience.

Learning points.

• Suture granulomas can mimic fluorodeoxyglucose-positive malignant lesions.

• Suture granulomas are difficult to differentiate from haematological cancers as both conditions exhibit proliferation of inflammatory and immune cells.

• These lesions can occur at various time frames including decades following initial operation.

• May be asymptomatic and cause no issues for the patient, thereby questioning the need to manage surgically.

• Non-absorbing suture materials, particularly silk, with their higher likelihood of forming inflammatory responses and suture granulomas, should be avoided during cancer resections.

Ethics statements

Patient consent for publication

Obtained.