What's your diagnosis? Solitary hydatid cyst of the soleus muscle.

A 40-year-old woman with pain and swelling in the right leg was seen one year after the initial occurrence of the swelling. She had no such swelling or symptoms beforehand. She lived on a farm. On physical examination there was 6 cm of hypertrophy in the left cruris, causing a palpable mass with pain and without any neurovascular impairment (Figure 1). Increased pain was observed during the push-off stance of gait. No other systemic signs were observed. Lung CT, bone scintigraphy abdomen and pelvic CT, the complete blood count, the erythrocyte sedimentation rate and blood chemistry were all normal. On plain X-rays bony structures were normal with only a slight increase in soft tissue density. On the MRI we observed a 6×14-cm cystic mass entirely within the soleus muscle (Figure 2).

Figure 1

Preoperative appearance of the limb.

Figure 2

T1- and T2-weighted MRI images of the soleus muscle.

(see answer on page 307)