A 54-year-old man presented at the emergency department with low back pain and a 2-day history of a low-grade fever (maximum at-home measurement, 37.6°C). The pain had begun 1 month previously with an insidious onset. The visual analog scale for pain was 4 of 10 at rest, worsening with activity and resolving at night. His temperature on admission was 37.3°C in the emergency department. He had no alcohol abuse or smoking history, and his medications included atorvastatin and irbesartan.
An oval mass of the lumbar region was obvious during inspection. On palpation, it was rather warm, hard, immobile, and about 6 cm in size and the patient did not experience pain with this mass (Fig. 1). There were no findings from the neurological examination, and a straight leg raise test (Lasègue’s sign) was negative. Radiographs of the lumbar spine were normal. The laboratory results showed a slightly elevated white blood cell count of 11.200/μL with mild eosinophilia (7.2%). The results from a complete metabolic panel were normal, but the C-reactive protein was elevated (3.6, with normal values < 0.5), as was the erythrocyte sedimentation rate (34, with normal values <10). Magnetic resonance imaging (MRI) scans demonstrated a 4.8 × 6.8-cm, thin-walled cyst with no septation at the level of L2-L4, located inside the longissimus thoracis muscle. The lesion extended from the subcutaneous tissue of the lumbar spine to the transversospinalis muscle group, penetrating the posterior layer of the thoracolumbar fascia (Fig. 2).
Computed tomographic (CT) scans were performed on the brain, lungs, and liver. All scans were negative for cysts. Treatment with albendazole (15 mg/kg/day orally) was initiated preoperatively.
One week later, a complete surgical excision of the mass was performed with the patient under general anesthesia. During the procedure, a fully equipped anesthesiology team was on high alert in case of a rupture of the cyst. The mass was removed intact (Fig. 3), with care taken to maintain adequate margins of healthy tissue.
On histopathologic examination, the cyst wall consisted of dense, fibrous tissue with variable numbers of mononuclear cells, multinucleated giant cells, and increased eosinophils. Palisading histiocytes were present mainly on the inner surface. The foci of foreign-body giant cell reaction around eosinophilic, acellular, and refractile (Periodic acid-Schiff+) material were present (Figs. 4, 5, and 6).
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