A meibomian cyst, commonly referred to as chalazion, is a non-infectious inflammatory disease of the sebaceous glands on the eyelids that presents as an enlarging lump over the course of days or weeks without resolution to topical antimicrobial therapy. Acne rosacea and seborrheic dermatitis increase the risk for meibomian cysts. Blurred vision may be encountered with larger meibomian cysts, while pain is almost always absent. The diagnosis rests on clinical criteria, but because malignant tumors may have an identical clinical presentation, a histopathological examination is advocated.
A meibomian cyst (also known as chalazion) arises when the outflow of the meibomian glands in the eyelids is blocked, leading to the accumulation of the secretions produced and the formation of a cyst    . It is defined as a benign lipogranulomatous collection that develops from non-infectious causes, which is the crucial feature distinguishing it from a stye, which is formed because of a bacterial infection   . The clinical presentation is characterized by the appearance of a painless lump on the eyelid that grows over a period of days or weeks  . The lump exhibits a variable degree of tenderness, swelling, and redness (depending on the stage) that often overlaps with the presentation of a stye, but all of the aforementioned signs eventually subside  . Both upper and lower eyelids may be the location of a meibomian cyst, which can sometimes appear in multiple sites . In some cases, the cyst may be large enough to induce mechanical ptosis or astigmatism, leading to symptoms such as blurred vision and deficits in the visual field  . A cosmetic discomfort is also an important complaint and is often the main reason for a visit to the physician . Several cutaneous disorders have been associated with an increased risk for meibomian cyst formation, including rosacea, seborrheic dermatitis, and blepharitis  .
With a properly conducted physical examination and a meticulously obtained patient history, the initial diagnosis of a meibomian cyst can be easily made. The typical appearance of a lump on the eyelid without the presence of pain (mainly seen when a stye develops) is a hallmark of this clinical entity. Some patients report ineffective use of topical antimicrobials , which points to a non-infectious type of inflammation. Although the physician can clearly visualize the lesion and make a solid diagnosis based on physical findings only , some authors recommend further evaluation of the lump through histopathological methods   . The primary reason is that several tumors, particularly sebaceous cell carcinoma (carrying a mortality rate of 20% in the absence of an early diagnosis and up to 50% when tumor spreading occurs) have an identical clinical presentation   . Disruption of the skin and ulceration are suggested as signs indicative of a malignancy instead of a meibomian cyst , but they may not always be present. The identification of a lipogranulomatous content and multinucleated giant cells with an abundant white blood cell infiltrate are main findings on microscopy of meibomian cysts . Noninvasive meibography, designed to evaluate the morphology of the meibomian glands, is a potentially useful procedure to discriminate between a chalazion and a sebaceous cell carcinoma .