Unruptured large human cyst: a rare case

Perineal epidermal lesions are uncommon, with only a few research papers available on the topic. Since these lesions are diverse in origin and can range from benign to malignant, it can be difficult to distinguish between them. A variety of lesions are evaluated in the differential diagnosis of perineal cystic lesions, but perineal epidermal cyst is uncommon. An epidermal cyst is a benign congenital anomaly of the ectodermis. Epidermoid cysts can be found all over the body, however they are uncommon in the perineum area.

We discuss the case of a human perineal cyst in an adult female presenting to the Department of General Surgery with painful perineal swelling. The patient was advised to undergo ultrasound (US) and MRI for further evaluation and results were reported.

an introduction

EC(s) are benign tumors that commonly affect the scalp, face, neck, back, and chest. They are usually asymptomatic when they are small and developed, but can become symptomatic as a result of a secondary infection or when they grow to a size that displaces or causes a collective effect on the surrounding anatomic tissues [1]. Epidermal cysts, or epidermal cysts, form when epidermal cells multiply in a narrow skin space. Ectodermal tissue misplaced during embryonic development, adipose capillary unit obstruction, or traumatic or surgical epithelial element implantation are all possible causes of epidermal cysts. [2-4]. Variable radiological characteristics, anatomically specific and symptomatic perineal cystic lesions make diagnosis difficult.

CT and MRI make it possible to examine the entire intestinal wall layer as well as the tissues surrounding the rectum, making it easier to characterize these abnormalities further. MRI has a strong radiological diagnostic value because it can accurately show the structure of the perineum. As a result, magnetic resonance imaging (MRI) has been largely used to investigate perineal sac lesions [5].

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A 45-year-old female patient presented to the Department of General Surgery with complaints of pain in the perianal region for three years. Symptoms have worsened sharply in the past week. There was no history of trauma to the patient. On local examination, there was a slight swelling under the skin in the area of ​​the birth incision. There was no evidence of a localized rise in temperature or redness on examination. The patient was notified of a high-frequency soft tissue ultrasound of the perianal region.

On ultrasonography of the perianal region, there was a well-defined cystic lesion with internal echoes within the subcutaneous level. The patient was further advised to have a pelvic MRI in view of the complete evaluation of the lesion and an understanding of its extension.

Subsequently, MRI performed showed a peripherally well-defined, thin-walled, signal intensity lesion that was hyperintense on T2WI/STIR and isointense on T1WI measuring ~9.0 × 4.0 × 3.4 cm (AP × TRANS × COR) (Fig. 26). The lesion displaced the lower parts of the coccyx superiorly and anteriorly abuts the posterior wall of the anus. In the back the lesion extended to the subcutaneous level. The lesion showed no signs of localized infiltration and the surrounding fascial planes were well visualized.

The patient was subsequently advised with FNAC (fine needle cytology) that showed components of keratin (Fig 1). The patient was sent back to surgery and a postoperative sample was sent for evaluation to confirm the presence of an epidermal cyst.


Epidermal cysts are rich in keratin and bound by stratified squamous epithelium. The meiosis of epidermal cells within the closed lumen of the dermis is involved in the pathophysiology of epidermal cysts. Men are twice as likely than women to develop cysts. It can occur at any age; Although statistically it is most common in the third to fourth decades of life. Epidermal cysts usually appear on the face, head, neck, and trunk. Perineal involvement is rare. Only a few cases of unexpected intracyst haemorrhage and epidermal cyst malignancy have been described in the literature [6,7].

The US is often the primary method of choice in evaluating masses in the perianal region. Selected soft tissue lesions can be diagnosed based on some clinical and imaging features. Epidermoid cysts are fairly common on ultrasound, but may have a non-specific and hazy appearance, and the altered imaging features require additional imaging. Ultrasound is useful in determining the anatomical location and proximity to adjacent structures, and features such as echo, volume, and margins can be seen routinely. [8]. Epidermoid cysts have classic cystic characteristics; However, it can be solid or cystic. It is circular to oval, with a well-defined avascular mass in the dermis and subcutaneous tissue, as well as dorsal vocal amplification and lateral shading. [9].

Both CT and MRI scans are used to identify epidermal cysts and to determine surgical removal procedures. CT is useful to confirm the diagnosis of a large dermoid cyst, but not for small dermoid cysts. On computed tomography, a well-coated mass of heterogeneous densities can be detected, which reflects a mixture of lipids and keratin [10].

The findings of an MRI of epidermal cysts are affected by the cyst’s maturity, compaction, and the amount of keratin it contains. [11]. Epidermoid cysts appear as hyperintense T1 hypointense and T2 masses with restricted spread when located throughout the body. T2 hypointense foci may occur within the lesion due to the presence of keratin [12]. Most epidermal cysts do not show contrast enhancement. However, edge improvement can be found in 25% of cases [13].


MRI is one of the best-selected examinations for the evaluation of perineal lesions, which helps in understanding the nature, extent and involvement of adjacent soft tissues with high accuracy. Non-ruptured epidermoid cysts usually show well-defined mass lesions with low signal intensity, few bright foci on T1-weighted MRI images, and high signal intensity on T2-weighted MRI.

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