Hindawi Publishing Corporation Case Reports in Pathology Volume 2013, Article ID 126541, 3 pages http://dx.doi.org/10.1155/2013/126541 Case Report Primary Subcutaneous Hydatid Cyst with Palisading Granulomatous Reaction Noorah Almadani, 1 Bader Almutairi, 2 and Ali H. Alassiri 1 1 Department of Pathology and Laboratory Medicine, King Abdulaziz Medical City, P.O. Box 22490, Riyadh 11426, Saudi Arabia 2 Department of Medical Imaging, King Abdulaziz Medical City, P.O. Box 22490, Riyadh 11426, Saudi Arabia Correspondence should be addressed to Ali H. Alassiri; aliassiri@hotmail.com Received 24 October 2013; Accepted 17 November 2013 Academic Editors: K.-U. Choi and T. Yuri Copyright © 2013 Noorah Almadani et al. Tis is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Palisading granulomatous reactions are prominent microscopic characteristics that are seen in many diseases. Isolated subcuta- neous cystic echinococcosis is rarely documented. Palisading granuloma as a host immune reaction to Echinococcus granulosus in an isolated primary subcutaneous hydatid cyst has been reported only once before. In this report, we are describing a 53-year-old male who developed a slowly growing subcutaneous thigh mass. Light microscopy confrmed the presence of hydatid cyst. Further radiological workup for liver and lung has not shown any visceral hydatid focus. 1. Introduction Cystic echinococcosis is an important tapeworm disease caused by Echinococcus granulosus, usually locating in liver or lungs, and subcutaneous location or extension is rare. Palisading granulomatous reactions have been docu- mented in several diseases. Furthermore, rare cases of echinococcosis that show palisading granulomatous reaction have been documented. Herein, we report an unusual clin- ical presentation with an uncommon microscopic feature of isolated subcutaneous cystic echinococcosis that shows prominent palisading granuloma. 2. Case Report 2.1. Clinical Features. A 53-year-old male presented with a right thigh mass slowly growing over 10 years. Physical examination revealed a rounded, frm mass in the right upper thigh with no skin changes. Magnetic resonance imaging revealed a cystic well-circumscribed heterogenous sof tissue mass involving the mid-upper right thigh just inferior to the right inguinal ligament (Figures 1(a) and 1(b)). Te mass measures 13.7 cm in maximum dimension. Te patient underwent total excision of the mass with safe margins and his postoperative clinical course was uneventful. 2.2. Gross Features. Macroscopic examination of the received excisional biopsy showed a well-circumscribed subcutaneous cystic mass that measures 13.5 cm in maximum dimension covered by skeletal muscle tissue. Te outer surface is intact and the section surface revealed multiloculated cystic mass containing thick yellow gelatinous material. 2.3. Microscopic Features. Formalin fxed and parafn em- bedded sections displayed variably sized cysts palisaded by granulomatous reaction (Figure 2(a)). Te cyst contained PAS+ laminated membranous structures typical of Echino- coccus cyst walls better appreciated on high magnifcation (Figures 2(b) and 2(c)). Tese are intensely stained with PAS stain. 2.4. Clinical Correlation. Subsequent serological assay for hydatid disease was positive. Computed tomography of chest, abdomen, and pelvis did not reveal any primary lesion. 3. Discussion Hydatid disease is a parasitic infestation caused by the tapeworm Echinococcus granulosus. It is endemic in Saudi Arabia and the Middle East countries especially in rural areas