Chest wall tuberculosis in children: a mimicker of bone tumour

Abstract

Osteoarticular tuberculosis of flat bones of the chest wall such as sternum, scapula and rib is extremely rare in children. Because of its atypical clinical presentation mimicking malignant bone tumours, diagnosis remains a challenge. Histological and microbiological diagnosis remains confirmatory. Antitubercular therapy is the cornerstone in management.

Background

Osteoarticular tuberculosis (TB) is one of the rare forms of extrapulmonary TB in children. It accounts for 1%–5% of all forms of TB and 10%–17% of extrapulmonary forms.¹ Among osteoarticular TB, the spine (Pott’s disease) remains the most common site of involvement, followed by joints and long bones. Bone TB in atypical locations like sternum, scapula and ribs are rare and mostly considered as bone tumours on initial evaluation due to clinical similarity. Here, we present two cases of TB of the chest wall (sternum and scapula) presenting as bone swelling and evaluated for bone tumours.

Case presentation

Case:1

A 12-year-old boy had complaints of swelling in the chest wall just below the neck, which gradually increased over 2 months. It was associated with minimal pain. There was no history of fever, trauma, contact with TB and chronic cough. He was receiving treatment for the above complaints from a local practitioner and referred to us as a suspected case of bone tumour due to lack of clinical improvement. His weight and height were 31.8 kg and 143.5 cm, respectively, and within the normal age limit. The child’s physical examination revealed a localised swelling of 5×5 cm over the sternum with mild tenderness. However, no redness or warmth was observed (figure 1A). Systemic examination was normal. Initial laboratory tests revealed that the haemoglobin was 113g/L with a raised erythrocyte sedimentation rate (ESR) of 60 mm/hour. Mantoux test was positive. Chest radiograph posteroanterior view showed heterogeneous opacities in the right lung field (figure 1B). Chest radiograph lateral view showed an osteolytic lesion of the manubrium sternum (figure 1C). Ultrasonography of the chest confirms the osteolytic mass. Hence the possibility of primary bone tumour versus osteomyelitis was initially considered. CT scan could not be performed due to financial reasons. Fine-needle aspiration cytology was performed from the swelling, which showed granulomatous inflammation with caseating necrosis. Acid fast bacilli stain was positive. The Xpert Mycobacterium tuberculosis/rifampicin ultra was also positive for TB and sensitive to rifampicin. Screening ultrasound abdomen for other foci was normal. Because of rare location and unusual presentation, HIV serology was also performed, which was non-reactive.

Figure 1.

Showing fluctuant swelling over the sternum depicted by the white arrow (A), Chest radiograph showing heterogeneous opacity in the left upper lobe depicted by the red arrow (B) and chest radiograph lateral view showing an osteolytic lesion in manubrium sternum shown by black arrow (C).

The child was started on category-1 antitubercular therapy (ATT) with a regimen of four drugs isoniazid (H), rifampicin (R), pyrazinamide (Z) and ethambutol (E) for 2 months and three drugs (HRE) for 10 months. On follow-up after 12 months of ATT, the child’s general condition improved, and the swelling completely subsided with radiological evidence.

Case: 2

A 12-year-old girl had swelling over the right side of the chest wall in the back, which gradually increased over the past two and half months (figure 2A). She also had intermittent fever. She had no history of contact with TB and swelling elsewhere in the body. She was receiving treatment from a local hospital for the aforementioned complaints, and MRI performed during that time suggested a lytic bone tumour, most likely to be Ewing’s sarcoma (figure 2B). Then the patient was referred to us for further management. Her weight and height were 27.7 kg and 143.2 cm, respectively. Local examination revealed a discrete, firm swelling over the right scapula of 7×7 cm with mild tenderness. No warmth or redness was observed and systemic examination was normal.

Figure 2.

Swelling over the right scapula (A), MRI right scapula showing lytic lesion with contrast enhancement shown by black arrow (B), chest radiograph posteroanterior view with normal lung fields (C).

Among the initial investigations, the mantoux test was positive, chest radiograph posteroanterior view was significantly normal for lung fields (figure 2C). CT chest showed expansile lytic lesions in the right scapula with multiple thin-walled cystic lesions in bilateral lower lobes of the lungs and mild mediastinal lymphadenopathy. A provisional radiological diagnosis of probable Ewing’s sarcoma with metastasis versus TB was considered. Because of the uncertainty in the diagnosis, ultrasound-guided fine-needle aspiration of the lesion was performed. It has shown features of necrotising inflammation suggestive of TB. The Xpert RIF/MTB ultra was also positive for TB and sensitive to rifampicin. Screening ultrasound abdomen performed for any other foci was normal. The child was started on category 1 ATT with a four-drug regimen isoniazid, rifampicin, pyrazinamide and ethambutol for 2 months and three drugs (HRE) for 10 months. The child improved clinically after starting ATT with reduced swelling along with the improved general condition.

Outcome and follow-up

Both the children of the index cases were improved clinically after 1 year of antitubercular therapy and doing well on follow-up.

Discussion

Chest wall TB in flat bones such as the sternum, scapula and ribs accounts for less than 1% of osteoarticular TB in children.^2–4 Chest wall tumours are infrequent and most of them are malignant like Ewing’s sarcoma, rhabdomyosarcoma and osteosarcoma.⁵ Though rare, both tumours and TB can present as mass lesions in the chest, but the parents and physicians have always worried about the poor prognosis of tumours compared with TB. Hence in clinical practice, because of the rare and unusual presentation of TB mimicking a mass lesion, most clinicians consider bone tumours as one of the initial primary diagnoses even in TB endemic countries. It was the same scenario in both cases presented here.

The pathogenesis of osteoarticular TB has two different mechanisms. Like other osteoarticular TB, the chest wall TB of flat bones is usually secondary to the primary focus in the lungs. They spread mostly through lymphohaematogenous mode or directly from the latent pleural focus by pressure necrosis when the host immunity weakens. This spread is favoured by certain bone characteristics like increased vascularity in the metaphysis of the weight-bearing bones and bone marrow with abundant lymphoid cells with few macrophages. This is the most common mechanism seen in children. Sometimes it can present with an isolated primary bone infection like primary complex. It is usually seen in infants and younger children. It can be multifocal, exudative and infective.⁶ Most of the children with chest wall TB reported in literature are older children and they usually had some form of underlying pulmonary involvement as seen in our index cases. Isolated chest wall TB is predominantly seen in younger children and very rarely reported in the literature. This suggests that age is an important factor in pathogenesis and clinical presentation.⁷

Although TB presentation at atypical sites is common in immunocompromised people, it can also be seen in immunocompetent individuals from TB endemic countries. Although most of them have a primary focus in the lung, they do not have respiratory symptoms. Systemic features of TB such as fever, loss of appetite and loss of weight are not common.⁴ Most of the patients present with swelling, pain and restricted movements of the affected joints and also do not have any epidemiological contact. A similar clinical presentation was observed in our patients.

Among the blood tests, the ESR is high in most of the patients. However, it is non-specific and cannot differentiate TB from other bone lesions like malignant tumours and suppurative osteomyelitis. A plain X-ray can be useful but normal in the early stages. Lesions if visible are best seen in lateral view than anteroposterior view for sternum. Imaging with CT has various manifestations like osteolytic lesions, abscesses, periosteal reactions and microcalcifications (highly suggestive). As the disease progresses, there can be evidence of localised osteopenia, articular erosions and reduced joint spaces.⁸ Bone marrow oedema and intraosseous abscess are the common findings in MRI.⁹ Apart from identifying the lesions, these are also helpful to find the pulmonary involvement and mediastinal lymphadenopathy. However, most of these lesions are nonspecific and often difficult to distinguish from malignant bone tumours and suppurative lesions.

The histological and microbiological confirmation remains the investigation of choice. Because of this unusual location for TB, atypical clinical and non-specific radiological presentations mimicking bone tumour, patients present very late and got a delay in initiation of the appropriate treatment. Due to lack of evidence about healed status in osteoarticular TB, it is generally advised to give an extended course of ATT with 2 months of intensive phase and 10 months of continuation phase.¹⁰ Most of them improve with ATT alone, with few requiring surgical drainages.

Learning points.

• Chest wall tuberculosis in children is rare and often have atypical presentation mimicking malignant bone tumour

• A high degree of suspicion is needed for early diagnosis.

• Radiological findings are mostly nonspecific; histological and microbiological confirmation is warranted

• Antitubercular therapy is the mainstay of treatment. Often needs extended course.