Primary subcutaneous implantation hydatid cyst

Hydatid cyst (HC) is a parasitic infestation caused by the larval form of Echinococcus granulosus (EG).[1] The defi nitive hosts for EG are dogs, wolves, and foxes; while intermediate hosts include sheep, goats, and cattle. Humans are a coincidental (accidental) intermediate host.[2] The disease is more frequent in sheep rearing countries of the Middle East, Central Europe, Australia, and South America.[1,2] The commonest organs affected are the liver (70%) and lungs (10-15%).[1-3] Other locations are extremely rare. Soft tissue HC occurs in 2.3% of cases and is secondary to involvement of other structures.[3] Structures immune to development of HC include hair, teeth, and nails.[3] Primary subcutaneous HC is very rare[1-5] and primary subcutaneous implantation HC is unknown.

undergone cholecystectomy it was revealed that on that particular date prior to her cholecystectomy another patient had undergone operation for liver hydatid.
At operation, the entire cyst along with the germinative membrane was removed and sent for histopathology [Figure 3].The postoperative period was uneventful and the patient was discharged on the 10 th postoperative day after stitch removal.Histopathology was consistent with HC [Figures 4a and b].The patient was put on albendazole (15 mg/kg) in divided doses for 3 months.At 6 months follow-up the patient is doing well and no sign of recurrence could be detected by physical examination and imaging.

DISCUSSION
[3][4][5] In secondary cysts, there is an evidence of primary location in some other organs like liver or lung.Primary subcutaneous HC are rare.In our case, the HC was located subcutaneously, there was no past history of previous surgery for HC, and no HC was found in any other organs.Therefore, our patient was diagnosed as having primary subcutaneous HC.
The mechanism of primary subcutaneous localization is unclear. [6,7]he two proposed mechanism include systemic dissemination via lymphatic route and direct spread.Direct spread may occur from inoculation (wasp bite) [8] or implantation of daughter cyst due to improper sterilization of contaminated instruments and drapes.
[3][4][5][6][7] At times the cyst may get superinfected or cracked and may simulate an abscess or a cancer. [7]diological imaging is useful for diagnosis, showing the size, location, relationship to adjacent organs, and type of the cyst.[3][4][5][6][7] However, it is rarely positive for cysts in extrahepatic and extrapulmonary locations. [8]It is often associated with false-negative and false-positive results. [8] Therefore in endemic zones, awareness of the physician complimented with radiological and serological investigations remains the mainstay of preoperative diagnosis particularly for the unusual presentation of the disease.
Preoperative diagnosis of subcutaneous HC is also possible by fi ne needle aspiration cytology (FNAC). [2,3,6,7]The presence of diagnostic hooklets ensures correct identifi cation, as in our case.No urticaria or anaphylactic reactions have been reported as a complication of this procedure.Differential diagnosis of subcutaneous HC includes teratoma, abscess, or fi bromatosis. [7]Subcutaneous HC do not attain big size unless there is penetration to deeper layers. [8]3][4][5][6][7][8] Incidentally, subcutaneous cysts are more prone to rupture.In such a situation, the fl uid contents should be removed, the laminated membrane excised, and the cyst irrigated with protoscolicidal solution.[3][4][5][6][7][8] These drugs play an important role, preoperatively for sterilization of the cyst and postoperatively in case of spillage.][4][5][6][7][8] Our hypothesis of primary implantation subcutaneous HC was based on the following facts, (a) the patient hailed from an endemic zone, (b) past history of open cholecystectomy with no evidence of HC at that time, (c) a review of the list of operations performed at the place of open cholecystectomy revealed operation for liver hydatid on another patient prior to open cholecystectomy on this patient, (d) development of the cyst 6 months post-cholecystectomy in the vicinity of incision line, (e) no evidence of cyst in any organs other than the current location, and (f) the possibility based on review of literature reporting development of subcutaneous HC following wasp sting. [8]

Figure 1 :
Figure 1: Preoperative photograph showing the abdominal swelling and previous cholecystectomy scar