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Hand Surgery, Vol. 19, No. 2 (2014) 265–267 © World Scientific Publishing Company DOI: 10.1142/S0218810414720241

INTRAOSSEOUS EPIDERMOID CYST DISCOVERED IN THE DISTAL PHALANX OF A THUMB: A CASE REPORT John Junghun Shin, Ki-Yeon Kwon and Jin-Rok Oh Department of Orthopedic Surgery Wonju College of Medicine, Yonsei University Wonju, Republic of Korea Received 6 October 2013; Revised 17 November 2013; Accepted 18 January 2014 ABSTRACT Intraosseous epidermoid cyst is considered a rare benign inclusion cyst found mainly in the skull and phalanges. Once the cyst is differentiated from other similar lesions, the cyst can be treated with simple curettage, seldom requiring additional managements. We experienced this rare case that had been treated successfully without complication. Keywords: Epidermal Cyst; Inclusion Cyst; Phalanx; Finger.

INTRODUCTION

site, biopsy with pathologic confirmation is necessary to differentiate from malignancy or inflammatory bone disease.2 We encountered a case of intraosseous epidermoid cyst which occurred in the distal phalanx of left thumb and make a report with literature review.

Intraosseous epidermoid cyst is a rare benign mass of epithelial cell origin, and it usually occurs in the skull, maxilla, mandible, sternum, vertebrae, radius, femur, tibia, finger, and toe. The aetiology of the mass is still under debate. Some believe that trauma causes accidental implantation of epithelial cells into bone, and cases without trauma history represent congenital origin of the cyst which epithelial cell is entrapped during fotal development. Rarely, iatrogenic seeding of the epithelial cells within bone is noted as a possible cause.1 Simple radiography reveals radiolucent and expansile lesion. Because curettage is sufficient to treat intraosseous epidermoid cyst whereas malignancy may require amputation of affected

CASE REPORT A 77-year-old male patient visited the outpatient clinic with swollen and penetrating lesion at his left thumbnail. Two weeks before his visit to outpatient clinic, the patient became aware of sinus with exudate on his left thumb nail (Fig. 1). The spherical mass was palpable and tender, and base of the nail was protruded. Motor function and sensory were within normal

Correspondence to: Dr. Jin-Rok Oh, Department of Orthopedic Surgery, Wonju College of Medicine, Yonsei University, 162 Ilsan-dong, Wonju, Gangwondo, 220-701 Wonju, Republic of Korea. Tel: (þ82) 33-741-1343, Fax: (þ82) 33-746-7326, E-mail: [email protected] 265

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Fig. 2 Intraoperative photographs show the finger and mass after removal of nail and curettage.

(A) (B) Fig. 1 The patient had visited our department after noting drainage from a sinus formation from his left thumb nail (A). Simple radiography shows radiolucent expansile lesion just below the nail (B).

limits. Simple radiography showed radiolucent and expansile mass within distal phalanx. Under local anaesthesia, the fingernail was removed, and curettage and excision of relatively well-demarcated mass with size of 1:5  1  0:5 cm was performed. The wound was repaired including replantation of the removed fingernail (Fig. 2). Histopathologic examination of the mass concurred with the findings of intraosseous epidermoid cyst (Fig. 3). For 18 months, the patient experienced no complication or recurrence (Fig. 4).

(B) Fig. 3 The pathologic evaluation confirmed an epidermoid cyst. Under microscope, the cyst wall of the specimen revealed keratinizaing stratified squamous epithelial linings. Haematoxylin-eosin staining: (A) 10 magnification and (B) 100 magnification.

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Intraosseous Epidermoid Cyst Discovered in Distal Phalanx of a Thumb

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Fig. 4 Post-operative photographs taken at follow-up show complete healing of the nail without sinus (A). No recurrence is shown on follow-up radiography (B).

DISCUSSION Intraosseous epidermoid cyst is a benign cystic mass, and the hand is the site where the mass occurs commonly. About 95% of the mass occurring in finger are found in distal phalanx.1 Prevalent age is between 25 and 50 years old, and its occurrence is twice more in males than in females.3 The cyst grows slowly and gradually, and a patient usually complains of swelling, pain, tenderness, erythema, or fingernail deformity. Simple radiography shows relatively well demarcated circular mass that is radiolucent and expansile, and it may demonstrate thinning of cortical bone and osteolysis.4 Pathophysiology is still unknown, but traumatic or iatrogenic implantation of epithelial cell or epithelial cell’s entrapment to bone during embryogenesis serves some understandings to its origin.1,2 Treatment is curettage of the cyst, and necessity of bone graft is not usually required.4 Recurrence is rare, and finger function is seldom affected. Histopathologically, it features stratified squamous epithelial cell lining that contains keratin deposits.1 Cyst rupture, infection, or pathologic fracture may form periosteal reaction or foreign body granuloma.4 Often, it is difficult to differentiate from enchondroma which also has radiolucent property on simple radiography, but spotty calcification is usually present in enchondroma. Chronic

osteomyelitis, intraosseous ganglion, simple bone cyst, aneurysmal bone cyst, osteoid osteoma, glomus tumor, giant cell tumour, and metastatic cancer are other lesions that must be differentiated. To make a differential diagnosis, MRI, ultrasonography, or fine needle aspiration should be considered.5 To sum up, intraosseous epidermoid cyst is a rare benign mass that occurs mainly in the distal phalanx of a finger originating from traumatic or iatrogenic causes. It must be differentiated from other similar lesions for proper treatment. The cyst can be cured simply with curettage and rarely recurs.

References 1. Kalsotra N, Singh M, Sharma S, Singh D, Intraosseous epidermoid cyst of the finger phalanx: A case report, Orthop Res Rev 71–73, 2010. 2. Carroll RE, Epidermoid (epithelial) cyst of the hand skeleton, Am J Surg 85:327–334, 1953. 3. Fisher ER, Gruhn J, Skerrett P, Epidermal cyst in bone, Cancer 11:643– 648, 1958. 4. Van Tongel A, De Paepe P, Berghs B, Epidermoid cyst of the phalanx of the finger caused by nail biting, J Plast Surg Hand Surg 46:450–451, 2012. 5. Wang BY, Eisler J, Springfield D, Klein MJ, Intraosseous epidermoid inclusion cyst in a great toe. A case report and review of the literature, Arch Pathol Lab Med 127:e298–300, 2003.

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Intraosseous epidermoid cyst discovered in the distal phalanx of a thumb: a case report.

Intraosseous epidermoid cyst is considered a rare benign inclusion cyst found mainly in the skull and phalanges. Once the cyst is differentiated from ...
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