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Acta M ed Kinki Univ Vol.39, No.2 97-99, 2014 An unusual case of retrobuibar orbital apocrine hidrocystoma Narihiko Hirano, Shinichi Asamura, Noritaka, Isogai Department of Plastic and Reconstructive Surgery, Kinki University Faculty of Medicine, Osakasayama, Osaka 589-8511, Japan Abstract A 61-year-old woman was referred to our department from an eye clinic with a 3 year history of progressive proptosis of the right eye. M agnetic resonance imaging revealed a mass with a cystic appearance located in the retrobulbar orbital region. Histological features of the excised cystic tumor were characteristic of apocrine hidrocystoma (AH). It is thought to arise from a cystic dilatation of the sweat glands contiguous with the skin s surface. In the Introduction Apocrine hidrocystoma (AH) is a type of cystic tumor that is typicallysmall and commonly located in the head and neck region, particularly in the periorbital region. Pathohistologically,AH usuallyoriginates from a dilated sweat gland. In this report, we describe the clinical features of a relatively unusual case of AH presenting in the retrobulbar orbital region, and thecourseoftreatment. Wethen discuss our findings with reference to previous research,and present our hypothesis regarding the origin of AH. Case report A 61-year-old woman was referred to our department from an eye clinic with a 3 year history of progressive proptosis of the right eye and decreasing visual acuity. Her Hertel measurements were 17 and 21 mm on the left and right sides, respectively. The patients were normal about preoperative light reflex and eye operative specimens, no epidermal elements were observed near the cystic structure. The absence of contiguous subcutaneous tissue was a rather unusual phenomenon. Although rare,AH should be considered in the differential diagnosis of a cystic tumor presenting in the retrobulbar orbital region. Key words: Apocrine hidrocystoma, Sweat gland, Orbit, Cyst movement. Magnetic resonance imaging (MRI) with gadolinium contrast revealed a mass with a cystic appearance located anteriorly in the medial intraconal space of the right orbit[Figure 1]. Treatment was based on a swinging eyelid approach. Using a lateral rim removal approach,osteotomywas performed with a bone saw at a level just above the fronto-zygomatic suture and above the zygomatic arch, followed by advancement to deep areas using a bone chisel and wood hammer. Fracture was then induced at the zygomatic bone-sphenoid bone suture area by holding and mobilizing the bone fragment using bone forceps, which facilitated wide visualization ofthe deep corner area. After the globe had been gently removed laterally,the tumor was found to be buried within the orbital fatty tissue. With meticulous dissection of the fatty tissue, the tip of the tumor was detected, allowing it to be subsequently isolated and resected. Macroscopically, the cystic tumor was observed to have a thin wall and contain clear fluid with a purplish tint[Figure 2] . The piece Received July 11, 2014; Accepted August 8, 2014 97 N.Hirano et al. Fig.3 Fig.1 Preoperative MRI A : Horizontal plane, B: Coronal plane Histological features The arrow shows apocrine snouts which are characteristic of AH. the cyst wall was formed by myoepithelial cells in which the long axes ran parallel to the cyst wall. The cells of the inner layer were mildly columnar with occasional apocrine snouts. Papillaryprojectionsextended from thesecretory layer into the cyst cavity, showing decapitation secretion. These features are all characteristic of AH[Figure 3] . Discussion Fig.2 A swinging eyelid approach The arrow shows AH is isolated and resected. of the bone tissue previously removed from Fronto-zygomatic region was replaced at the original site. Upon completion of the procedure, proptosis was no longer noticeable. The patient experienced a transient postoperative diplopia in the peripheral gaze that resolved within 2 months. The postoperative visual acuity improved 0.3 to 0.7 on the right side within 2 weeks. Microscopic examination revealed a fibrous tissue wall lined by epithelium composed of double cell layers but with areas of occasional thickening. The outer layer of cells comprising 98 Hidrocystomas can be subdivided into eccrine and apocrine types. Although the eccrine type is more frequently associated with multiple lesions, the apocrine type (i.e., AH) typically presents as a solitary benign cystic tumor. Attributed to adenomatous cystic proliferation of the apocrine glands and characterized by cylindrical epithelia,AH is generallythought to arise from a cystic dilatation of the sweat glands contiguous with the skin s surface. In the operative specimens described here, no epidermal elements were observed near the cystic structure. From the viewpoint of histogenesis, the absence of contiguous subcutaneous tissue is a rather unusual phenomenon. AHs are benign cysts that arise from the apocrinesecretoryglands ofMoll and arecommonly located in the head and neck region, Although they have been observed in other areas of the body. Similar lesions have been reported on the outer surface of the eyelids, canthal areas, and the orbital rim. Shields emphasized that AHs typically develop around the medial canthus of the eyelid, but rarely within the orbit. The content of the orbital cavity is composed An unusual case of retrobuibar orbital apocrine hidrocystoma ofthe eyeball,extraocular muscles,nerves,blood vessels, lacrimal glands, and orbital fat tissue. The origins of their histogenesis are the neuroectoderm,surface ectoderm,and mesoderm that exists between the surface and neuroectoderm. The anterior portion of the ocular structures, including the eyelids, corneal epithelium, and lenses,is derived from the surface ectoderm. On the other hand, the posterior portion of the ocular structures, including the retina, optic nerves, extraocular muscles, and orbital fat tissue, is derived from the neuroectoderm and mesoderm. Regarding the histogenesis of the present case of AH, it is extremely difficult to clarifyits origins from an embryological perspective. Although thepathogenesisofAH isnot entirely clear, Epidemiological research indicates that these lesions often appear between 30 and 70 years ofage and then grow slowly. None ofthe hypotheses regarding the etiology of the cyst origin,such as a trauma or orbital bone remodeling during childhood,has been proven scientifically. We hypothesize that AH arises from tissue originating from the surface ectoderm during embryological development. While this tissue evanesces on further ocular development under normal circumstances,It doesnot evanesce for known reasons under unusual circumstances, providing the conditions for cyst from the embryonal remnant tissue many years later. We cannot propose any other rational explanation for the oncogenesis of AH. References 1. Khashayar S, Amor K (2006) Hidrocystomas ―A Brief Review. MedGenMed 8: 57-60 2. McCord CD Jr (1981) Orbital decompression for Graves disease. Exposure through lateral canthal and inferior fornix incision. Ophthalmology 88: 533-541 3. Golden BA, Zide MF (2005) Cutaneous cysts of the head and neck. J Oral MaxillofacSurg 63: 1613-1619 4. Chin SC,Chen CY,Zimmerman RA (1998)Pericoccygeal hidrocystoma. Am J Neuroradiol 19 : 587-588 5. Rosen WJ, Li Y (2001) Sudoriferous cyst of the orbit. Ophthal Plast Reconstr Surg 17: 73-75 6. Vignes JR, Franco-Vidal V, Eimer S, Liguro D (2007)Intraorbital apocrine hidrocystoma. Clin Neurol Neurosurg 109 : 631-633 7. Shields JA, Shields CL (2004) Orbital cyst of childhood-classification, clinical features, and management. Surv of Ophthalmol 49 : 281-299 8. Moore KL, Persaud TNV (1993) The development human-clinically oriented embryology. by W.B.Saunders Copmany. 9 . Foster CA, Bertram JF, Holbrook KA (1988) Morphometricand statistical analyesdescribing thein utero growth of human epidermis. Anat Rec 222: 201-206 99