Sinonasal organising haematoma (OH) is an uncommon, non-neoplastic condition, which is locally aggressive. It was first reported in Japanese literature in 1917 by Tadokoro as a “blood boil of the maxillary sinus”.1 It has also been referred to as haematoma,2 haematoma-like mass,1 pseudotumour3 or organising haematoma of the maxillary sinus.4 The maxillary sinus is known to be the most commonly involved sinus.5,6 The aetiopathogenesis of this entity is still ambiguous.

The disease is mostly unilateral and usually presents with nasal obstruction and epistaxis.4,5 Contrast-enhanced CT scan of the paranasal sinuses may reveal bony destruction, erosions and heterogeneous soft tissue densities in the involved sinuses. The close resemblance of these radiological findings to a maxillary sinus malignancy creates a diagnostic dilemma. Multiple biopsies are often performed because they often result in a “negative biopsy”. Complete surgical excision either by an endoscopic or a combined sublabial and endoscopic approach is the definitive treatment for OH. Total excision also enables the pathologist to systematically exclude other pathological diagnoses which may present in a similar manner.

Awareness regarding OH is still very low, both among the clinicians as well as the pathologists. In the present report, we aimed to study the clinical profile, management and treatment outcomes of all patients diagnosed with sinonasal OH seen over the last 6 years.

We conducted a retrospective chart review of patients who were diagnosed with OH between 2010 and 2016 at a tertiary care hospital in South India. Data regarding demography, clinical features, radiology, histopathology, treatment and follow up was collected and analysed. The study was approved by the Institutional Review Board.

OH is a rare, benign condition with locally aggressive behaviour. The pathogenesis of the lesion is haemorrhage into a sinus (typically, the maxillary sinus) and formation of a chronic haematoma. This is followed by organisation through fibrosis and neovascularisation. Song et al.4 have described “organization” as “replacement of blood clots by fibrous tissue” and introduced the terminology “organising haematoma of the maxillary sinus”. The previously used terminologies were haematoma,2 haematoma-like mass,1 pseudotumour3 and organised haematoma. The cause for haemorrhage is often unclear. All except two of our patients were hypertensive and this could be a cause for the bleed. Two patients who were hypertensive had coagulation disorders, further increasing their risk for an intrasinus bleed. When bleeding occurs within the nasal cavity, the clots are easily expelled either by forceful blowing of the nose by the patient, manual removal or ciliary action along with mucus. In contrast, when bleeding occurs into a closed sinus, particularly if the blood clot is large, a chronic haematoma results. This haematoma then gets replaced by fibrous tissue and newly formed blood vessels, leading to the formation of OH.

Most reports suggest that the commonest paranasal sinus to be affected is the maxillary sinus.5,6 Obstruction of the sinus ostium leads to negative intraluminal pressure and decreased ventilation.7 In our study, the maxillary sinus was involved in all the patients. Additionally, in some patients the lesion extended beyond the confines of the maxillary sinus. Previously, only three cases (one involving frontal sinus and two involving sphenoid sinus -) of extra maxillary sinonasal OH have been reported.5 We report four new cases of extra-maxillary involvement of OH involving the anterior and posterior ethmoid sinuses (n=4), frontal (n=2) and sphenoid sinuses (n=1). The mean age of presentation in our series was 47.4 years with a male predominance, which is similar to that reported in other studies.4,5,7,8

The aetiopathogenesis of OH is still not clearly understood. Accumulation of blood in the maxillary sinus is believed to be the trigger for OH. The cause of bleeding into the sinus may be trauma, surgery, bleeding diatheses or a haemorrhagic lesion within the sinus. Some authors have suggested that either a ruptured aneurysm of a medium-sized vessel related to the affected sinus or inflammatory erosion of an arterial wall may be causative as well.8 The aetiological factors related to this could be aggressive fungal infection, radiation therapy and recurrent epistaxis.7,9 In a study by Choi et al.,5 about 30% (6 out of 17 patients) of patients with OH were hypertensive and were on aspirin. The antiplatelet agent was proposed as a possible causative factor in these patients. In our study, 80% of the patients were hypertensive. Among those who had hypertension, one patient had factor XI deficiency and another. had thrombocytopenia. The effect of these comorbidities could have been cumulative. None of the patients in our series were on any antiplatelet medications. Three patients, however, gave history of recent nasal surgery and this could also have been a cause for haematoma formation. In view of the high prevalence of hypertension among our series of patients diagnosed with OH, we believe that hypertension itself may be a risk factor for developing OH.

A number of theories have been proposed to explain pathogenesis of this condition.7–10 The “negative spiral theory” proposed by Omura et al.10 is based on immunohistopathological evidence,11 and is the most accepted theory at present. Collection of blood in the paranasal sinuses with poor sinus ventilation and drainage can lead to haematoma formation, which remains in the sinus for a long time. As part of the biological healing processes, necrosis, fibrosis and hyalinisation occur leading to a capsule formation around the haematoma, thus preventing its reabsorption. Later, neovascularisation develops within the capsule, where the new vessels are weak, and rebleeding might easily occur. Recurrent intracapsular bleeding, leads to the eventual formation of OH. Progressive expansion causes pressure demineralisation of adjacent bony sinus walls, leading to remodelling and subsequent bony erosion. Imayoshi et al.12 have observed that vascular endothelial growth factor (VEGF) and its receptors (VEGFR2) are related to the neovascularisation seen in OH.

The radiological appearance of sinonasal OH is rather nonspecific. On CT scans without contrast the lesion is seen as a large mass causing expansion of the maxillary sinus with bony erosion and various degrees of heterogeneous high attenuation within the lesion. Post contrast, patchy heterogeneous enhancement is seen, probably due to the neovascularisation.7 The surrounding inflammed sinus mucosa in spite of the bony erosions points towards a benign process.9 On MRI scanning, the lesion is heterogeneous in signal intensity on both T1 and T2 weighted images and is always well demarcated from the surrounding structures. The heterogeneous signal intensity reflects the various components contained within the lesion, such as haemorrhage in various stages, fibrosis, and varying amounts of vascular proliferation. T2 weighted images demonstrate a hypointense peripheral rim which corresponds histologically with an attenuated fibrous pseudocapsule. This biphasic appearance is an important imaging characteristic of OH.4 Hur et al.13 have demonstrated irregular nodular, frond-like, papillary or cerebriform enhancement in all their cases.

OHs are diagnostic dilemmas clinically and radiographically, mimicking benign or malignant neoplastic processes. Various differential diagnoses to be considered for unilateral mass in the sinonasal cavity detected on CT and MR images include mucocoele, fungus ball, inflammatory polyp, cholesterol granuloma, inverted papilloma, haemangioma, and carcinoma. Contrast-enhanced CT or MRI scanning of the paranasal sinuses is extremely useful in excluding mucocoele, fungal ball, inflammatory polyp, and cholesterol granuloma as they do not usually enhance. Inverted papilloma primarily shows a characteristic convoluted cerebriform pattern on T2- or enhanced T1-weighted MR images. Clear cut bony destruction associated with adjacent tissue invasion is a hallmark of carcinoma. In contrast, OH typically shows thinning, expansion and smooth erosion of the sinus walls. The most difficult lesion to differentiate from OH both clinically and radiologically is sinonasal haemangioma, especially the cavernous type.

On histopathological examination OH cases show a combination of vascular ectasia, recent and old haemorrhage, oedema, fibrin exudation, fibrosis and hyalinisation and neovascularisation. Occasional cases may show some inflammatory granulation tissue in the subepithelial tissue. The primary histopathological differential diagnosis considered in the present series was haemangioma. Although dilated blood vessels and vascular proliferation which occur in haemangioma were seen in the cases studied, the presence of abundant fibrin deposits with hyalinisation, haemorrhage and neovascularisation precluded the diagnosis. Surgical samples were processed in entirety to avoid missing any overt focus of atypia or malignancy. Fungal stains were done to exclude any invasive fungal sinusitis. Despite the presence of clinical and radiological features which bear a strong resemblance to malignancy, a negative histopathology result does not warrant further surgery. A high index of suspicion with careful histopathological examination is essential to arrive at the diagnosis.

The treatment of OH is complete surgical excision. Various approaches such as lateral rhinotomy, Caldwell-Luc, Denker's surgery, combined endoscopic and Caldwell-Luc approach and endoscopic sinus surgery have been described.1,4,5 Only 2 of our patients required a combined approach (Caldwell Luc plus endoscopic sinus surgery) to completely remove the disease. Most patients (80%) were managed by an endonasal endoscopic approach alone. We noted that we adopted a less invasive procedure with each subsequent case in our series and this could be attributed to increased awareness of the condition with time.

Sinonasal OH is a rare, benign, locally aggressive disease which mimics sinonasal malignancy both clinically and radiologically. Histopathology is confirmatory. Complete endonasal endoscopic surgical excision is sufficient in the majority of patients.

Since this is a retrospective study, informed consent was not required. However, the institutional review board approval was obtained.

The authors declare no conflicts of interest.