An unusual location of an epidermoid cyst, the middle phalanx of the middle finger: A case report

DOI: https://doi.org/10.21203/rs.3.rs-1469449/v1

Abstract

Introduction:

Epidermoid cysts are cutaneous cysts frequently observed among farmers, factory workers, carpenters, and tailors due to their occupations' predilection for repetitive minor hand trauma.

Case Presentation:

A 66-year-old male laborer presented to our hospital with a swelling on the palmar aspect of his right middle finger. The swelling was accompanied by pain and an inability to work over the previous four months. A 2.5 cm × 2.5 cm smooth, tender, immobile, non-compressible hard swelling was detected just above the middle phalanx during the clinical examination on the volar aspect of the right middle finger. The diagnosis was confirmed by histopathology after excision. The patient's range of motion improved significantly following surgery, and his pain subsided.

Conclusion:

We present a novel location for an epidermal inclusion cyst and the importance of histopathologic evaluation in this case. Additionally, we emphasize the significance of extensively checking the cyst's epithelium to guarantee complete capsule removal and rule out any additional pathology.

Introduction

An epidermoid cyst is a cutaneous cyst with an epithelial lining similar to the epidermis. The cyst lining produces keratin. The term "sebaceous cyst" is no longer appropriate because no sebaceous glands are present. Other words used to describe epidermoid cysts include inclusion cysts, epidermal inclusion cysts, epithelial cysts, keratin cysts, implantation dermoid, and traumatic or post-traumatic epidermoid inclusion cysts. An epidermoid cyst might occur because of the implantation of epidermal elements into the dermis during any trauma or surgery. They are typically observed in farmers, factory workers, carpenters, and tailors because their occupation predisposes them to repeated mild hand trauma (1). The factors implicated in the formation of palmoplantar epidermoid cysts include HPV infection, UV exposure, and eccrine duct obstruction(2). Epidermoid cysts are more common in the elderly and patients taking medications like BRAF inhibitors such as imiquimod and cyclosporine, especially their face(3)

case report

A 66-year right hand dominant male laborer by occupation reported to our academic institution with swelling on the palmar aspect of the right middle finger. The swelling was associated with pain and the inability to work at his job for the past four months. He had first observed the swelling seven years ago after trauma due to hammer and chisel. It increased in size gradually over the years but posed a significant problem from the past four months. A 2.5 cm x 2.5 centimeters, smooth, tender, immobile, non-compressible firm swelling was observed during the clinical examination on the volar aspect of the right middle finger overlying the middle phalanx (Images 1 and 2). There was no evidence of the central punctum (that is, the clogged orifice of the pilosebaceous follicle commonly seen in other anatomical locations). We suspected an epidermoid cyst because of a history of trauma. The differentials included giant cell tumor of the tendon, pilar cyst, foreign body granuloma, hemangioma, ganglion, and lipoma. We did the X-ray to rule out the presence of any foreign body owing to the history of trauma (Image 3).

A finger tourniquet made from a glove was used to prevent bleeding during the excision of swelling under a wrist block. Before making the incision, aspiration was performed, which resulted in a dry aspirate. The cyst burst open during dissection resulting in spillage of cheesy material, confirming the diagnosis of an epidermoid cyst. (Images 4 and 5). The histology confirmed the diagnosis (Images 6 and 7). The histopathology revealed a lining of stratified squamous epithelium with a granular layer along-with keratin arranged in a lamellated pattern as its content (Image) with the presence of the giant cells, new vessel formation, and lack of rete ridges.

The patient's range of motion improved significantly after surgery, and his pain subsided. The sutures removal was done after ten days, and the follow-up was unremarkable.

Discussion

Epidermoid cysts are caused by the growth of epidermal cells inside a defined dermal region. The lipid composition of the epidermal cyst is identical to that of the epidermis. The cysts contain cytokeratins 1 and 10. These cytokeratins are formed in the suprabasal layers of the epidermis and expressed within the cysts. The origin of this epidermis is almost invariably the hair follicle's infundibulum (4). Males are two times more likely than females to have epidermal cysts. Although Epidermoid cysts can occur at any age, they are most common in the third and fourth decades of existence. The most often affected location (32 percent, 33/103) is the head and neck, followed by the lower limb (26.2 percent, 27/103), the back (19.4 percent, 20/103), and the upper limb (9.7 percent, 10/103)(5). There have also been isolated reports of epidermoid inclusion cysts emerging from deeper tissues such as tendon and phalangeal bones. Phalangeal lesions most frequently affect the distal phalanx and present with variable degrees of pain, edema, nail deformity, and erythema on rare occasions. Several authors have proposed the development of a phalangeal cyst as a result of direct traumatic implantation of epidermal fragments into bone or migration of a portion insertion of the nail bed into the bone (4). In contrast to cysts at other locations, the palmoplantar cysts are not fluctuating and are immobile because of the thickness of the skin concerning anatomical areas.

Most epidermoid cysts are benign lesions but might become malignant in a rare case. A history of associated trauma and clinical examination is usually adequate to confirm the diagnosis of epidermoid inclusion cysts because they are frequently site-specific. Imaging studies do not result in a conclusive diagnosis but are recommended as part of a comprehensive assessment. The most common type of diagnostic modality used to diagnose the epidermoid cyst is the X-rays. The ultrasonography can be utilized but occasionally yields a definitive diagnosis. CT scan and MRI are helpful techniques in defining the architecture of soft tissue cancers, but this is rarely required to guide treatment. Fine-needle aspiration cytology (FNAC) is helpful if the amount of keratin or sebaceous material obtained is adequate to perform the cytological examination. The definitive diagnosis is made based on histopathologic findings of a cystic lesion. The cyst wall lining is created by stratified squamous epithelium, and the contents include lamellated keratin. The inflammatory reaction may or may not be present, and in either case, we may detect calcification in cysts that have been present for a long time.

Hand epidermoid inclusion cysts must be distinguished from ganglions, tendon sheath giant cell tumors, and lipomas, as well as bony and arthropathic swellings. Surgical therapy is only required for symptomatic cysts because most hand dermoid cysts are benign. The sudden growth in size frequently indicates complications such as rupture, infection, or malignant transformation. When hand function is impaired, treatment entails the complete removal of the cyst. The surgery can be performed under a brachial plexus or wrist block while wearing a pneumatic tourniquet applied over the arm or a finger tourniquet tied near the MCP joint.

Conclusion

In this case, we demonstrate a novel location for an epidermal inclusion cyst and the value of histopathologic examination. We also stress the importance of thorough inspection of the epithelium surrounding the cyst for complete removal of the capsule to prevent recurrence or omission of any other pathology.

Declarations

Declaration of Interest

We did not receive any specific support from funding agencies in the public, commercial, or not-for-profit entities.

Ethical Statement

We described the technique to the patient in her native language and obtained her approval to submit the article and accompanying photographs for publication.

References

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