Perineal and right femoral hydatid cyst in a female with regional paresthesia: a rare case report.

Background: Hydatid cyst is a zoonotic disease caused by the parasite Echinococcus granulosus. The tapeworm larvae can create cyst in different areas of the body, especially the liver and lungs; however, the formation of the cyst in the perineal and femoral regions are very rare. The unusual location of the cyst can help us with the differential diagnosis of soft tissue mass(es) in this location, especially in endemic areas. Diagnosis of this disease is crucial because if the cysts are ruptured during surgery, the fluid inside can cause anaphylactic shock.

Case Presentation: Our case is a 55-year-old woman with the chief complaint of a painful mass in the right thigh and perineal area with progressed pain and paresthesia to the right thigh and shin. The patient had no history of fever, abdominal pain, digestive dysfunctions, or chest pain. The vital signs were normal, and there was no family history. Physical examination showed that the skin over the mass had no discoloration, and the size was around 5.7 cm long. The result of the ultrasonography examination showed a cystic mass with suspicion toward the femoral hernia. After a CT scan, the result of secondary workups was a multi-lobular cystic mass with no connection to the abdominal region, which suggested a hydatid cyst. The patient underwent spinal anesthesia and surgery, a cystic mass with ecto- and endocyst, with clinical similarity to a hydatid cyst, was removed with wide margins, and the cyst wall was kept intact. In the next step, the specimen was sent for histological examination that confirmed cystic hydatidosis. The Post-surgical Abdominal and thoracic Ultrasonography screening were used to exclude relapse, and medical therapy was given for 3-6 months. An 18-months follow-up demonstrated no reoccurrence and no newly formed cyst.

Conclusions: Although rare, femoral hydatid cyst can occur in some cases, especially in endemic areas. We highly recommend our colleagues consider ruling out cystic hydatidosis in any patients complaining of regional mass(es), mostly painless, presenting with adjacent tissue compression with or without manifestation of an allergic reaction.