Case Report: A seventy-year-stable chest wall bronchogenic cyst with sudden enlargement: coincidence or connection with a concurrent thymic carcinoma?

INTRODUCTION

Bronchogenic cysts arising in the chest wall are uncommon. This report describes a unique case of a chest wall bronchogenic cyst that exhibited delayed proliferation after seventy years of stability, concurrently presenting with a separate anterior mediastinal thymic carcinoma.

CASE PRESENTATION: A 75-year-old woman presented with a six-month history of gradual enlargement of a long-standing, previously stable suprasternal mass. Computed tomography revealed a well-circumscribed subcutaneous cyst and a separate anterior mediastinal mass. Both lesions were completely excised. Histopathology confirmed the chest wall lesion as a bronchogenic cyst and the mediastinal mass as a poorly differentiated squamous cell carcinoma of thymic origin (Masaoka-Koga stage I). The patient recovered well with no recurrence at follow-up.

DISCUSSION: While sudden enlargement of bronchogenic cysts is documented, delayed growth after an exceptionally prolonged quiescent period is exceedingly rare. The concurrent discovery of a histologically distinct yet anatomically adjacent thymic carcinoma raises the question of a potential pathological interaction beyond coincidence. Common mechanisms for cyst enlargement, such as infection, haemorrhage, or secretory obstruction, were absent. We hypothesise that paracrine stimulation by factors secreted from the thymic carcinoma may have disrupted the cyst's homeostasis, prompting its secondary growth. This hypothesis warrants further investigation through molecular analysis of similar cases.

CONCLUSION

We report an exceptionally rare instance of delayed growth in a thoracic wall bronchogenic cyst, occurring after more than seven decades of quiescence and coincident with an anatomically adjacent thymic squamous cell carcinoma. This finding underscores the necessity for comprehensive evaluation of long-standing masses that undergo change; it also provides significant clinical insights, documents a unique case, and suggests avenues for investigating the underlying mechanism.