A New Metric Classification System for Surgical Management of Retrosternal Goitres

By Hamid Mukhtar¹, Hira Zahid¹, Imran Mohib Khan¹, Saad Siddiqui², Bushra Haider³, Shehzad Saeedullah¹

Affiliations

1. Department of Otolaryngology, Northwest General Hospital and Research Centre, Peshawar, Pakistan
2. Department of Radiology, Northwest General Hospital and Research Centre, Peshawar, Pakistan
3. Department of Education, Northwest General Hospital and Research Centre, Peshawar, Pakistan

doi: 10.29271/jcpsp.2025.06.708

ABSTRACT
Objective: To introduce a new metric classification system based on preoperative CT scans in the management of retrosternal thyroid pathologies.
Study Design: Descriptive study.
Place and Duration of the Study: Department of Otolaryngology, Northwest General Hospital and Research Centre, Peshawar, Pakistan, from June 2017 to 2023.
Methodology: Five hundred and eleven thyroidectomy cases were retrospectively reviewed, identifying 68 with retrosternal extension and 41 with preoperative CT scans showing retrosternal goitres (RSG). Using the thoracic inlet plane as a reference, a new metric-based classification system was developed and analysed, categorising RSG into three grades based on CT measurements. Statistical analysis was performed using SPSS version 25, and the association between RSG grades and the need for sternotomy was evaluated using the Chi-square test at 5% significance.
Results: The 41 patients had retrosternal goitres (RSG), which were classified into three categories based on the length from the thoracic inlet on preoperative scans. Grade I represented RSG length of less than 3 cm (15/41) from the thoracic inlet. Grade II ranged from 3-6 cm (22/41), and Grade III exceeded 6 cm (4/41). Grade I RSGs were exclusively managed through a conventional cervical approach, whereas 31.8% of Grade II and 75% of Grade III cases required sternotomy.
Conclusion: This classification offers a simple, metric-based framework that uniquely predicts the likelihood of sternotomy, simplifying preoperative planning and improving surgical outcomes during retrosternal thyroid surgeries.

Key Words: Classification, Goitre, Retrosternal, Sternotomy, Thyroidectomy.

INTRODUCTION

The word goiter, which means swollen throat, comes from the Latin phrase tumidum gutter, which in turn is from the Latin gutturia, meaning throat. A thyroid gland weighing over 40g is often classified as goitre. A goitre that extends past the thoracic inlet has been referred to by the terms retrosternal, substernal, intrathoracic, or mediastinal. There is no clear consensus in the literature regarding the precise definition of a retrosternal goitre (RSG). The literature identifies four definitions of RSG, one of which describes it as a thyroid gland extending below the thoracic inlet in the operative posture. It has also been defined as a thyroid gland that reaches the level of the aortic arch. Katlic et al. proposed that a thyroid with more than 50% (or the majority) of the gland located below the thoracic inlet is classed as retrosternal.¹ Goldenberg and Lindskog defined it as a thyroid reaching the level of T4 (on chest x-ray).²

Based on some studies, RSG occurs in between 0.2 and 45% of thyroidectomies. This is likely because different clinicians have used different definitions for RSG.³ Patients with RSG may experience symptoms due to pressure on the oesophagus, nerves, and vascular structures, as well as obstructive airway symptoms, and less frequently, superior vena cava syndrome.⁴ Between 5 and 40% of RSG cases are asymptomatic and are discovered incidentally through thorax computer tomography scan (CT) or chest radiography. The best test to scan and identify intrathoracic goitre components is a CT scan of the neck and chest.⁴

Because of the risk of continued thyroid growth and impending airway compromise, surgery is generally considered the best option for treating RSG, even in asymptomatic patients.⁵ Although it is generally agreed that RSG can be removed with a cervical incision, certain circumstances may call for an additional extra- cervical procedure such as a sternotomy or thoracotomy.⁶

This study aimed to develop a new metric classification system based on CT scan results for patients with RSG to help with preoperative planning for such patients. By using the thoracic inlet as a stable, consistent landmark, Mohib’s classification ensures standardisation in measurements, reduces variability in clinical interpretation, and improves surgical planning by providing clear guidelines for determining the need for sternotomy.

METHODOLOGY

This descriptive study was conducted retrospectively at the Department of Otolaryngology, Northwest General Hospital and Research Centre, Peshawar, Pakistan. The study examined 511 individuals who underwent thyroidectomy between June 2017 and June 2023. Out of the 511 cases, 68 had a retrosternal extension. Only 41 patients had a preoperative CT scan, which showed an RSG.

The inclusion criteria were patients of either gender and age with goitres having retrosternal extension and a preoperative CT scan. Patients having goitres but no retrosternal component and without a preoperative CT scan were excluded. Since it was a retrospective study, all patients fulfilling the inclusion criteria were selected through consecutive sampling techniques. The authors used the plane of the thoracic inlet as a reference for determining retrosternal thyroid gland enlargement.

Ethical approval (Ref: IRB&EC/2023-GH/089) was sought from the Institutional Research and Ethical Review Board Hospital, Dated 18^th October 2023. The data for this study were collected by reviewing the patients’ medical records, and information was extracted from hospital databases, including patient demographics (age and gender), clinical records, and radiological findings. Preoperative CT scans were reviewed to identify cases of RSG and measure the extent of retrosternal extension using the thoracic inlet plane as a reference. Details regarding surgical management, including the use of conventional cervical approaches or sternotomy, and the number of sternotomies done, were analysed.

The proposed new classification system, which is named Mohib’s classification of retrosternal goitres, divides this pathology into three grades based on the length in centimetres from the thoracic inlet on preoperative CT scans (Table I). Grade I (mild) represents an RSG length of less than 3 cm from the thoracic inlet, Grade II (moderate) measures 3-6 cm, and Grade III (severe) indicates RSG greater than 6 cm (Figure 1). Mohib’s classification system was analysed in association with the need for sternotomy in each category. All data were systematically recorded in a structured format for subsequent analysis.

Table   I:   Mohib’s   classification   for   retrosternal   goitres.

Mohib’s classification of retrosternal goitres (Measurement from the thoracic inlet on the CT scan in centimetres)
Grades	Measurement
I (mild)	<3 cms
II (moderate)	3-6 cms
III (severe)	>6 cms

Table  II:  Sternotomy requirement for different grades of retrosternal goitre (RSG).

Sternotomy	Grade I	Grade II	Grade III
No sternotomy	15 (100%)	15 (68.2%)	1 (25%)
Sternotomy performed	0 (0%)	7 (31.8%))	3 (75%)
Total cases	15	22	4
Chi-square test was used to calculate p-value. Pearson’s Chi-square = 11.053, p-value = 0.004

Figure 1: RSG Grade I, II, and III showing length of 20 mm (2 cm), 50.4 mm (5 cm), and 95 mm (9.5 cm), respectively.

Figure 2: Graph showing the rising trend of a possible sternotomy being directly  proportional  to  the  length  of  the  retrosternal  goitre.

The data were analysed with SPSS for Windows version 25. Median (IQR) was determined for quantitative/numerical variables such as age after checking the data normality through the Shapiro-Wilk’s test. Frequencies and percentages were calculated for categorical variables such as gender and RSG grading. Chi-square tests were used to analyse the association between RSG grades and the requirement for sternotomy, keeping p-value ≤0.05 as statistically significant.

RESULTS

Out of 511 thyroid surgeries from June 2017 to 2023, 41 patients were identified as having an RSG, confirmed preoperatively on a CT scan. Patients’ median age was 57 (IQR = 19.50) years, ranging from 30 to 73 years. Among the 41 patients, 82.9% (n = 34) were female and 17.1% (n = 7) were male. Right lobe RSG was observed in 43.9% (n = 18) of cases, while left lobe involvement was present in 56.1% (n = 23).

The classification system revealed that 15 (36.6%) patients had Grade I RSG (<3 cm), 22 (53.7%) patients had Grade II RSG (3–6 cm), and 4 (9.7%) patients had Grade III RSG (>6 cm). All Grade I RSG cases (100%) were successfully managed with a conventional cervical approach, with no requirement for sternotomy. In contrast, 31.8% (n = 7) of Grade II patients and 75% (n = 3) of Grade III patients required sternotomy.

A Chi-square test confirmed a statistically significant relationship between RSG grades and the need for sternotomy (Pearson’s Chi-square = 11.053, p = 0.004, highlighted that higher grades are associated with an increased likelihood of sternotomy (Table II, Figure 2).

DISCUSSION

The RSG in this study was considered as a thyroid gland descending below the thoracic inlet, as it refers to constant anatomic landmarks that are easily recognised both radiologically and during surgery. A secondary mediastinal goitre results from the downward extension of an enlarged cervical thyroid gland and constitutes the majority of cases. In contrast, a primary mediastinal goiter arises from ectopic thyroid tissue.⁷ It is uncommon to see a primary mediastinal goitre, which is a goitre with a separate blood supply coming from the mediastinal vessels.⁸ Less than 1% of surgery patients have this kind of goitre.⁷ A cervical incision is typically used to treat the mediastinal thyroid.^9,10 It has been demonstrated that this strategy is sufficient in up to 97% of cases.¹¹ Thyroidectomy may need a thoracic approach in individuals where the gland cannot be removed safely through a cervical incision in order to achieve sufficient exposure and remove the gland without using risky traction.^9,12 Similar challenges, such as accessing the gland safely, can arise when dealing with neoplastic thyroid pathologies or revision cases.^13,14 However, some specialised centres may have the experience and competency of dealing with large retrosternal thyroids trans-cervically. A meta-analysis by Khan et al. revealed that 6% of patients with RSG required an extra-cervical approach.¹⁴ Unfortunately, the cases that call for a combined strategy are not always obvious to distinguish, and the choice to have such a strategy is frequently made during surgery.^15,16 A patient's decision to proceed with surgery with an unexpected risk of needing a sternotomy, which can greatly alter the surgical morbidity and outcome, must be made after taking into account their medical history, and having a detailed conversation with the patient and their family preoperatively.¹⁷

For any suspicion of RSG, a preoperative CT scan is required to assess its extent and anatomical relationships. With the exception of a few specific cases, magnetic resonance imaging (MRI) does not add much information to that provided by CT. The most significant predictors for the necessity for a sternotomy in the surgical management of RSG are obtained from cross-sectional imaging via a CT scan.^18,19

Before the proposed metric system classification, there had been other classification systems in place to help with the management of RSG.²⁰ Compared to systems using variable anatomical boundaries such as the aortic arch, Mohib’s classification leverages the thoracic inlet as a stable reference point. This eliminates inconsistencies and provides clear, reproducible guidelines for surgical planning. With this metric system, there will be clear grades based on exact measurements from the sternal notch, making this the first standardised classification system for retrosternal thyroids.

Previously, Huins et al. proposed a new classification system for an RSG based on a systematic review of its complications and management.²⁰ They classified RSG into three categories using the aortic arch as the landmark. However, the authors used the thoracic inlet as the reference point which was a constant bony landmark with minimal variations, unlike the aortic arch, which may vary from individual to individual and even by the RSG itself. Mercante et al. proposed a detailed classification system based on CT scan findings, again using the aortic arch as the landmark, and the addition of different planes of extension of goitre retrosternally, which may sometimes be difficult to follow and implement in patient management.²¹ In this study, the authors have kept it simple and have provided clear guidelines as to how this classification system helps in deciding when to involve a thoracic surgeon. All the previous classification systems have had a positive role to play in the management of retrosternal thyroid pathologies. However, in addition to these systems, the application of Mohib’s classification allows surgeons to predict the need for sternotomy with greater accuracy. This reduces intraoperative surprises, minimises surgical complications, and ensures better communication with patients regarding potential risks and outcomes. There will always be exceptions such as revision thyroid surgeries, malignant or complex thyroid pathologies, which will require a detailed multidisciplinary approach than just following any simple classification system.

In the region where this study was conducted, huge multi- nodular goitres are still relatively endemic. Ultrasound is the preferred initial radiological investigation, where it is established whether there is any retrosternal extension. If that is the case, then it is recommended to proceed to a CT scan of the neck and upper chest. All the retrosternal thyroid surgery patients have had a decent recovery with no lasting morbidities. This is probably because of the emphasis on preparing the patient adequately before the surgery is carried out.

This study introduces a novel, metric-based classification system that standardises measurements and improves surgical planning, outcomes, and patient safety. However, its retrospective design and small sample size may limit generalisability. Prospective studies with larger cohorts are needed to validate the accuracy and utility of Mohib’s classification across diverse settings.

CONCLUSION

The new and simpler Mohib’s retrosternal goitre classification system offers a novel approach that improves preoperative planning, enhances patient safety, and facilitates optimal surgical outcomes. Grade I and II can be managed through a conventional cervical approach. For Grade II, involving intra-thoracic surgeons during preoperative planning is recommended to address potential complications. However, Grade III may need the active involvement of an intra-thoracic surgeon. Future studies will be helpful in validating the utility of Mohib’s classification across diverse patient populations and healthcare settings.

ETHICAL  APPROVAL:
Ethical approval to conduct this study was obtained from the Institutional Review Board and Ethical Committee of Hospital and Research Centre (Ref. No: IRB&EC/2023-GH/089; Dated: 18^th October 2023).

PATIENTS’  CONSENT:
Informed  consent  was  obtained  from  the  patient.

COMPETING   INTEREST:
The  authors  declared  no  conflict  of  interest.

AUTHORS’  CONTRIBUTION:
HM: Data collection, manuscript writing, and data analysis.
HZ: Revision of the literature review for manuscript writing.
IMK: Conception and design of the work.
SS: Data analysis of the radiological aspect.
BH: Statistical analysis and revision for submission.
SS: Acquisition of data.
All authors approved the final version of the manuscript to be published.

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