Epidermoid Cyst Turned Out to be a Common Viral Infection in an Uncommon Site!

Sir,

Epidermoid cyst is one of the most common cysts lined by stratified squamous epithelium, containing keratin. It arises spontaneously from hair follicle infundibulum or due to the traumatic inclusion of epidermis.[1]

An 18-year-old healthy girl presented to us with a single, asymptomatic, lesion over the right upper medial thigh. The lesion was present for 4 months and gradually enlarging in size. On examination, a 1.2 cm × 1 cm, skin colored, soft to firm nodular lesion over right upper medial thigh was felt [Figure 1]. At its center, the surface skin was attached, and a black punctum was noticed. There was no umbilication. On pressing the lesion white creamy material comes out through the punctum. So, we have diagnosed it as an epidermoid cyst and excised.

Figure 1

Small nodular lesion over right medial thigh with creamy discharge

Biopsy stained with hematoxylin and eosin showed an acanthotic, lobulated epidermal cyst with numerous intracytoplasmic eosinophilic inclusion bodies within the inner lining of the cyst. Those inclusion bodies were typical Henderson–Paterson body [Figures 2 and 3]. Laminated and indented areas are seen within. So, we finally diagnosed it as epidermoid cyst invaded inside with molluscum contagiosum virus (MCV)!

Figure 2

Multiloculated lesion with the proliferation of epithelial cells with eosinophilic molluscum bodies inside the cytoplasm, ×10

Figure 3

Henderson-Paterson bodies/molluscum bodies, ×40

MC is a poxvirus with four types MCV1, MCV1a, MCV2, MCV3. MCV1 is the most common type that infects children. MCV2 is sexually transmitted and infect adults. Many varieties described such as papular, pedunculated, solitary, and giant. Facial disfiguring lesions also found in immunocompromised patients.[2] One report of epidermoid cyst in the lower eyelid along with few MC lesions over face turned out to be MC after the biopsy.[3]

Park et al. reported three cases of epidermoid cysts lined with MC over genitalia and he proposed the possibility of sexual transmission.[4] Co-inoculation during sexual trauma and MCV invasion from the epidermis within cyst are thought to be the reason for the presence of MCV within the cyst.[5] However, penetration through hair follicle and insighting cyst formation in the infundibulum may be a possibility. Here, in our case, close physical contact or fomite might be the route of transmission although any history of sexual exposure was not present.

Keeping in mind the previous reports, this type of lesion is not common. In any small, epidermoid lesion over thigh, genitalia, “epidermoid cyst with MC” should be considered as differential. This reporting is to point out an unusual presentation and differential diagnosis of a very common clinical condition.

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