Primary hydatid disease of the rib mimicking a chest wall tumor: a case report and structured review of the literature

Rationale Bone hydatid disease is rare, accounting for only 0.5% to 2.5% of all hydatid localizations, and costal (rib) involvement represents only a small fraction of these bone cases. Because clinical and radiological features are nonspecific, rib echinococcosis is easily mistaken for a primary or secondary bone tumor, and the diagnosis is frequently established only after surgical exploration. Case presentation A 60-year-old woman, a farmer from a rural, endemic area of northwestern Tunisia, presented with a painless, slowly enlarging swelling over the eighth right rib of two months’ duration, unaccompanied by fever, weight loss, or other systemic symptoms. Ultrasonography and computed tomography of the chest wall showed an expansile osteolytic lesion of the eighth rib with cortical rupture, heterogeneous multiloculated fluid content, and an exophytic vesicle; mild hypereosinophilia was present and hydatid serology (ELISA) was moderately positive. Plasmacytoma/myeloma and bone metastasis were excluded by protein electrophoresis, breast imaging and positron emission tomography. Intraoperative findings and parasitological examination of the cyst fluid (protoscoleces and hooklets) confirmed cystic echinococcosis. A diagnosis of primary costal cystic echinococcosis was retained. Interventions The patient underwent a right lateral thoracotomy centered on the lesion with segmental resection of the affected eighth rib, debridement of adjacent soft tissue, and 20% hypertonic saline protection and irrigation to prevent local seeding, followed by three 1-month cycles of oral albendazole (400 mg twice daily). Outcomes The postoperative course was uneventful. The patient was discharged on postoperative day three and remained symptom-free, with no clinical, imaging or serological evidence of recurrence at two years of structured follow-up (clinical examination, chest-wall ultrasonography, CT and serology, the ELISA becoming negative at 24 months). Conclusion Rib hydatidosis should be included in the differential diagnosis of an osteolytic costal lesion in patients from endemic areas, even when systemic symptoms and inflammatory markers are absent and serology is negative. In our experience, complete segmental resection respecting the principles of hydatid surgery, combined with albendazole, was associated with a favorable outcome at 2 years; longer follow-up is required because late recurrences of bone echinococcosis are well documented.