Aspergillus nodules: Natural history and the effect of antifungals

Aspergillus nodules are classified as a subset of chronic pulmonary aspergillosis. The optimal management approach is not known as their natural evolution following biopsy, the rate of progression to chronic cavitary pulmonary aspergillosis (CCPA) and the effect of antifungal treatment have not been described.

characteristics of patients with histologically confirmed Aspergillus nodules.In particular, the natural history of Aspergillus nodules, the effect of antifungal treatment and the rate of progression of unresected nodules to cavitating forms of CPA are not known.The published literature describing biopsy-confirmed Aspergillus nodules is limited mainly to relatively small case series where most patients were diagnosed following resection. 4As a result, there are no evidence-based recommendations on whether patients with Aspergillus nodules benefit from antifungal treatment, and the European CPA guideline recommendations for the management of Aspergillus nodules are therefore based largely on expert opinion alone. 2Here, we describe clinical features and outcomes of patients with biopsy-confirmed Aspergillus nodules referred to a national centre for chronic fungal infections, including a subset of patients diagnosed following surgical resection.The effect of antifungal treatment on the evolution of the nodules and the subsequent development of chronic cavitary pulmonary aspergillosis (CCPA) is explored.

| ME THODS
Patients with a diagnosis of 'Aspergillus nodule' documented by a clinician in the medical notes from January 2009 to July 2023 were identified retrospectively and extracted from the database of the National Aspergillosis Centre, Manchester, United Kingdom.A nodule was defined as a rounded opacity measuring up to 3 cm in diameter as per the Fleischner Society: Glossary of Terms for Thoracic Imaging, and lesions were excluded from the analysis if they were larger than 3 cm maximal diameter at the time of diagnosis. 1

| RE SULTS
Thirty-one patients with a diagnosis of Aspergillus nodule were found in the clinical database.Of these, 8 were excluded: 4 as imaging prior to biopsy had shown the lesion to be larger than 3 cm, 2 as CT scans were not available for review, 1 as the biopsy was through a transbronchial approach and was not thought to be a true representation of nodule tissue and 1 as squamous cell carcinoma was identified in the same sample.
Of the remaining 23 patients, 13 (57%) were diagnosed by CTguided biopsy whereas 10 (43%) were diagnosed by surgical resection.The mean maximum diameter on chest CT scan prior to biopsy was 20 mm (standard deviation ±7.0 mm).Table 1 shows the summary of patients' clinical characteristics.

| Aspergillus nodules diagnosed on CT-guided biopsy
Of the 13 patients who were diagnosed following a CT-guided biopsy, 8 patients received no effective antifungal treatment post biopsy and went on to have a repeat CT scan a mean of 15.5 months after diagnosis (range 5-28 months) (Table 2).Of these, the biopsied Aspergillus nodules were reported as smaller in 6 and as unchanged in size in 2 cases on repeat CT scan.However, in 4 patients there were new findings on the follow-up imaging concerning nodules other than the one biopsied, as follows (Table 2): 1. Patient 2: New ground glass nodules 10 months later; these were resolved 13 months later.No CCPA was diagnosed on follow-up.
2. Patient 8: New 3.5 cm cavitary lesion and rising Aspergillus IgG 7 months post biopsy (Figure 1).Antifungal treatment was started 8 months later for probable chronic cavitary pulmonary aspergillosis (CCPA).A subsequent CT scan showed improvement in the cavitary lesion following antifungal therapy.to 9 mm after 16 months.This was subsequently biopsied and proven to be squamous cell carcinoma.
Five patients received effective antifungal treatment following the biopsy (Table 2).These patients received a mean of 10.8 months of oral azole antifungals (range 3-21 months) before a repeat CT scan was done.The biopsied nodule was reported as smaller in 1 case and of stable size in 4. Two of the nodules reported as being unchanged in size post treatment developed an internal cavity with material suggestive of aspergilloma.In 2 patients, new multiple nodules were reported on post biopsy imaging: 1. Patient 4: This patient had a history of prior right upper lobe resection for aspergilloma.She presented with a 23-mm nodule with air fluid level and a 18-mm nodule with central soft tissue.
Following biopsy of the larger nodule, the nodules reduced in size to 14 and 12 mm, respectively, after 8 months of azole therapy.Antifungal treatment was stopped after a total of 12 months.She subsequently developed a 3.5 cm cavity with aspergilloma 3 years 2 months after the biopsy.A diagnosis of CCPA with aspergilloma was therefore made (Figure 2).Two patients were immunocompromised: one had a history of liver transplant on sirolimus and prednisolone and one had rheumatoid arthritis on methotrexate and adalimumab.Both were treated with antifungals, and both had stable nodules on treatment, 13 and 18 months after biopsy, respectively (Table 2).
Overall, 1 out of 8 patients who did not receive antifungals following biopsy developed CCPA after a mean observation period of 18.9 months.Out of those who received antifungals for at least 4 weeks after the biopsy, 1 out of 5 developed CCPA after a mean observation period of 40.6 months (Table 2).

| Aspergillus nodules diagnosed on surgical resection
Ten patients were diagnosed after surgical resection.Of these, one had no follow-up scan.Of the remaining 9 patients, none had a biopsy-confirmed recurrence of Aspergillus nodule during a mean follow-up period of 21.1 months post resection (range 5-41 months).
However, 3 of these 9 patients had new nodules on follow-up imaging, although none of them were biopsied due to low suspicion for malignancy.One patient had several new nodules up to 2 cm maximal diameter 12 months after resection.On subsequent scans these were stable so they were considered not clinically relevant and were Interestingly, in a 61-year-old male with a background of COPD who had resection of a 17-mm nodule, histology showed granulomatous inflammation with fungal hyphae with no invasion into the lung parenchyma.Aspergillus IgG was 74 mg/L.On 18S rRNA PCR Cladosporium species were detected in 4 out of 10 samples and by microscopy in 2 out of 10 samples.This patient had no new nodules on CT scan 18 months after resection and did not receive antifungal treatment.
TA B L E 1 Clinical characteristics of patients with histologically confirmed Aspergillus nodules.

Clinical characteristics (n = 23) Value
Age (mean, range) 67.The histological appearance of the Aspergillus nodules consisted of hyphae on a background of necrotic, granulomatous or fibrotic tissue.In a previously published cohort of 8 histologically confirmed cases, all the nodules demonstrated necrotising granulomas on histological examination. 3ne of the unresected Aspergillus nodules went on to enlarge on subsequent imaging, nor did they progress to other subtypes of CPA such as CCPA or aspergilloma, regardless of whether the nodules were cavitating or not.However, in 2 out of the 13 patients who did not undergo resection, CCPA lesions developed elsewhere in the lung, and in 1 of these cases this was despite the patient receiving antifungal therapy.This patient had a prior history of resected aspergilloma.Overall, our data suggest that radiological monitoring of Aspergillus nodules without the need for antifungal therapy may be an appropriate management strategy.Kang et al similarly reported overall favourable outcomes in a cohort of 80 patients with Aspergillus nodules, although around a third of the patients in their study had lesions which were >3 cm so were too large to be classified as nodules by radiological criteria. 4In contrast to our study, the vast majority (98%) of their patients had a solitary nodule at the time of diagnosis and only 4% had underlying COPD or asthma.Only 7 out of their 80 patients (9%) did not undergo resection of the nodule and, similar to our findings, none of these nodules had increased in size on follow-up imaging, including in two patients who did not receive antifungal therapy post biopsy.None of their 80 patients had recurrence of aspergillosis on follow-up.
Particular caution may be required in patients with multiple nodules.One of our patients went on to be diagnosed with lung cancer, therefore it should not be presumed that in patients with a biopsy confirmed Aspergillus nodule that all other nodules present at that time, or any subsequent new nodules, have the same aetiology.Our study has several limitations.We describe a relatively small number of patients, and this is a single site, retrospective study.Although the histological appearance of nodular tissue was consistent with Aspergillus in all cases, it should be noted that the fungal species was not confirmed in any of our cases, as samples were not sent for fungal culture or PCR.There may have been a selection bias as all our patients were able to undergo an invasive diagnostic procedure and outcomes may differ in those who are not suitable to have either lung biopsy or resection.Finally, the decision to treat only some patients with antifungals was based on clinician preference at the time of routine care, therefore the two groups may not be directly comparable.
In summary, conservative management of Aspergillus nodules without antifungal therapy may be an appropriate management strategy, although repeat imaging is recommended to ensure a cancer diagnosis is not missed and to monitor for the development of other subtypes of CPA, particularly in patients with multiple nodules.
All nodules were considered incidental findings.Patients were included in the analysis only if a histological sample from the lung nodule, obtained by CT-guided biopsy or during surgical resection, was available and reported by a histopathologist as showing fungal hyphae compatible with Aspergillus infection.The histological features, besides the presence of hyphae, were documented.Aspergillus IgG by ELISA (ImmunoCAP, cut-off 40 mg/L) within 6 months of the biopsy was recorded, if available.Demographics, underlying diseases, smoking status and antifungal treatment prescribed as part of routine care were recorded.Effective antifungal treatment for Aspergillus nodule was considered as being at least a 4-week course of an azole drug following the biopsy or resection.Duration of treatment of less than 4 weeks was classified as incomplete treatment.Using information obtained from radiological images and patient records, patients were assessed for the development of cavitary forms of CPA following the diagnosis of Aspergillus nodules, from the time of the biopsy until the last available follow-up point.Radiological features of the Aspergillus nodule were assessed by reviewing the chest CT scan performed immediately prior to the diagnostic procedure.The following characteristics of the nodules, as reported by the reviewing radiologists, were documented: maximal diameter, location, presence of additional nodules, presence of cavitation, spiculation or calcification.This study was a retrospective analysis of data collected during routine clinical care and therefore ethical approval or patient consent was not required.

3 .
Patient 10: Multiple new 6 mm nodules 24 months post biopsy.Thirteen months later, another 7 mm nodule was seen.The patient died from an unrelated reason.No CCPA was diagnosed on follow-up.4. Patient 12: Previously noted nodule which had grown from 2

2 .
Patient 7: This patient had a 19-mm cavitating nodule and, following biopsy of this nodule, he received 16 months of azole treatment before a scan was repeated.This showed the nodule to be stable.A total of 24 months of antifungal treatment was given.The nodule reduced in size to 15 mm 4 years post biopsy, but multiple new similarly cavitating nodules up to 8 mm appeared on the left side.Thirteen months later, the multiple new nodules had almost completely disappeared.He has not been diagnosed with CCPA.
not investigated further.No CCPA was diagnosed over a 10-year follow-up period.Another patient had a new 4 mm nodule 40 months after resection.No CCPA was diagnosed during 3 years and 1 month of follow-up.The third patient had a new nodule 41 months after resection.No CCPA was diagnosed up to 10 years later.Only 1 patient received antifungals for 3 months post resection, 7 did not and antifungal history was unclear for 1 patient.

Furthermore, one
of the patients identified in our database but not included in the final analysis was found to have both hyphae and evidence of neoplastic disease on biopsy of a nodule.The presence of hyphae therefore likely does not rule out cancer, underlying the importance of follow-up imaging to monitor the lesion.Half of our patients had negative Aspergillus fumigatus IgG at the time of diagnosis, suggesting that the sensitivity of this test is lower than for other subtypes of CPA and therefore a negative test does not rule out the diagnosis.2This may reflect a lower fungal disease burden or lack of immunological stimulation as compared to the other subtypes of CPA.Another possibility is that a proportion of these nodules are caused by different fungal species.We found evidence of Cladosporium in one patient, although more data are needed.Further work is required to assess whether there is a difference in outcomes between seronegative and seropositive Aspergillus nodules patients.Further work is required to ascertain if Aspergillus itself is the main driver of the development of the nodules, or if they are merely secondary to another disease process.It also remains to be seen if specific histopathological characteristics can be used to predict which nodules may progress over time and if patients with Aspergillus nodules have similar subtle immune defects seen in patients with other subtypes of CPA.6,7

F I G U R E 1
A 73-year-old male with COPD, heart failure and atrial fibrillation had a new 3.5 cm cavitary lesion and rising Aspergillus IgG 7 months after a biopsy confirmed Aspergillus nodule.CPA was diagnosed and antifungal treatment was started.F I G U R E 2 A 38-year-old female patient with a history of asthma, pneumothorax and prior right upper lobe resection for aspergilloma.(A) 18 mm biopsy-proven Aspergillus nodule.(B) 3.5 cm cavity with aspergilloma developed 3 years 2 months after the biopsy despite antifungal treatment.

gender Underlying disease Aspergillus IgG Max diameter pre biopsy (mm) No. of nodules at the time of diagnosis
6 (38-87) Gender, n (%) TA B L E 2 Data of patients who had Aspergillus nodule diagnosed with CT-guided biopsy.No Age,