Characterized by a dome-shaped, painless, firm, elastic mass that is a mobile nodule of yellowish-white or flesh-colored appearance with distinct borders, usually oval in shape and with a smooth surface. The size can be up to 4-5 cm, rarely larger. In most cases they appear on the scalp, extremely rarely on the face, trunk, limbs or buttocks. Cases of localization in the oral cavity have been reported. The nodule becomes hard when calcium salts are deposited. Trauma to the tumor causes marked edema, tenderness, redness, and sometimes ulceration and bleeding.

Clinical features are similar to those of the single pilar cyst. Usually the number of cysts does not exceed five (average 2-3). They may be grouped or scattered. In most cases they are localized in the hairy part of the scalp. Spontaneous rupture with discharge of chalky material without odor and blood admixture is possible.

Proliferating pilar cyst, also known as proliferating trichilemmal tumor, is a rare neoplasm that develops from a pre-existing trichilemmal cyst after trauma or inflammation and arises from hair matrix cells. It can also occur de novo (on unaltered skin) and in the setting of nevus sebaceous.

Clinically, it presents as a single soft, smooth-surfaced, flesh-colored nodule or plaque. Multiple lesions are seen in approximately 10% of cases. The size ranges from 1 to 25 cm (average 5 cm). In 90% of cases, it is located on the hairy part of the scalp, less commonly on the face, trunk, upper limbs, vulva, or buttocks.

The course is unpredictable and the process may be benign and slow or very rapid with histologic signs of malignancy (malignant proliferating trichilemmal tumor) with metastases to cervical and supraclavicular lymph nodes and soft tissues of the neck.

Tricholemmocystic nevus (nevus tricholemmocysticus) is an organoid epidermal nevus characterized by the presence of tricholemmal cysts in the form of yellowish or flesh-colored plaques along Blaschko's lines, along with multiple small verrucous hyperkeratotic papules. Lesions are found on the head, neck, trunk, extremities, palms, and soles. When localized on the scalp, diffuse alopecia is observed.

It is usually identified at birth, occasionally in early childhood. The etiopathogenesis is not well understood.

FLOTCH syndrome (Familial occurrence of total Leukonychia, Trichilemmal Cysts, and Ciliary Dystrophy with dominant autosomal Heredity) is a rare autosomal dominant genodermatosis characterized by the simultaneous development of multiple large trichilemmal cysts, total leukonychia (white nails), and ciliary dystrophy.