Epidermoid cyst of the phalanx of the finger caused by nail biting

Intraosseous epidermoid cysts of adjacent digits in a dog

Background

Intraosseous epidermoid cyst (IEC) is a rare, non-neoplastic, pathology in animals and humans that most commonly affects the distal phalanx. In dogs, it is important to differentiate this lesion from malignant digital tumours causing bone lysis. In previous reports, IEC has been described to affect only a single digit at the time of diagnosis which is usually based on histopathology. This is the first case report to describe immunohistochemically confirmed IECs affecting simultaneously multiple digits.

Case presentation

A 4-and-a-half-year-old female spayed Great Dane was presented with a 2-month history of progressive swelling of the distal phalanx (PIII) of digits IV and V of the right pelvic limb. Eleven weeks prior to presentation, the dog had a low-grade cutaneous mast cell tumour completely excised from the craniolateral base of its left pinna. A history of trauma to 1 of the nails of the same pes 4 years prior to referral was also reported. Examination of the right pelvic limb identified firm non-painful swelling of PIII of digits IV and V, with concurrent deformation of the nails. Radiographs of the right pes obtained by the primary veterinarian identified an expansile lesion of PIII of digits IV and V. Computed tomography identified large expansile lesions of PIII of digits IV and V, with associated cortical thinning and soft tissue swelling. Neoplasia was considered the most likely radiographic diagnosis. Histopathology of Jamshidi bone biopsies was consistent with intraosseous epidermoid cyst, which was confirmed with immunohistochemistry. Amputation of PIII of digits IV and V at the level of mid-PII was performed as definitive treatment. No recurrence of the lesion occurred during the 10-month follow-up period.

Conclusions

Intraosseous epidermoid cysts should be included in the differential diagnosis for expansile lesions affecting the canine digit. It is important to differentiate them from other digital lesions, with bone involvement, such as malignant digital tumours, which often require more extensive surgery for definitive treatment. The case herein highlights that this lesion can affect simultaneously multiple digits. Definitive diagnosis can be achieved by identification of keratin-producing epithelial cells on histopathology and confirmed by pancytokeratin labelling.

Intraosseous Epidermoid Cyst of the Radius

We report the rare case of an intraosseous epidermoid cyst of the distal radius associated with an acute infection in a 79-year-old woman.

Nail abnormalities identified in an ageing study of 30 inbred mouse strains

In a large-scale ageing study, 30 inbred mouse strains were systematically screened for histologic evidence of lesions in all organ systems. Ten strains were diagnosed with similar nail abnormalities. The highest frequency was noted in NON/ShiLtJ mice. Lesions identified fell into two main categories: acute to chronic penetration of the third phalangeal bone through the hyponychium with associated inflammation and bone remodelling or metaplasia of the nail matrix and nail bed associated with severe orthokeratotic hyperkeratosis replacing the nail plate. Penetration of the distal phalanx through the hyponychium appeared to be the initiating feature resulting in nail abnormalities. The accompanying acute to subacute inflammatory response was associated with osteolysis of the distal phalanx. Evaluation of young NON/ShiLtJ mice revealed that these lesions were not often found, or affected only one digit. The only other nail unit abnormality identified was sporadic subungual epidermoid inclusion cysts which closely resembled similar lesions in human patients. These abnormalities, being age-related developments, may have contributed to weight loss due to impacts upon feeding and should be a consideration for future research due to the potential to interact with other experimental factors in ageing studies using the affected strains of mice.

Intraosseous epidermoid cyst of the distal phalanx reconstructed with synthetic bone graft

Intraosseous epidermoid cysts are exceedingly rare. Known as pseudotumors, not true neoplasms, intraosseous epidermoid cysts usually involve the phalanges, the skull, and the toes. Intraosseous epidermoid cysts typically present as destructive osteolytic lesions on X-ray, mimicking malignant bone tumors. Here, we present two cases of an intraosseous epidermoid cyst in the distal phalanx treated with curettage and synthetic bone graft, followed by a review of the relevant literature. In both cases, the patient presented with a painful enlargement of the fingertip following a minor trauma. Magnetic resonance imaging demonstrated lesions involving the distal phalanx that had a low signal on T1-weighted imaging (WI) and a high intensity on T2-WI. In both cases, the lesions were not enhanced by gadolinium. Good remodeling and functional recoveries were obtained. For physically active patients with substantial bone defects, synthetic bone graft may be recommended.

An intraosseous epidermal cyst developing in a metacarpal bone after K-wire fixation: a case report

Intraosseous epidermal cysts (IECs) are rare benign lesions caused by the proliferation of epidermal cells within the bone. The pathogenesis of IEC remains unclear; however, trauma-triggered infiltration of the bone by epidermal elements has been suggested. Here, we present a case of an IEC in the metacarpal bone of the little finger associated with K-wire fixation for treatment of a fifth metacarpal fracture.

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 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.