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.