Rarely seen, the malignant counterpart to trichilemmomas is a trichilemmal
carcinoma, which requires surgical excision or Mohs.
These cystic lesions can be misdiagnosed as epidermoid cyst, cystic teratoma, hemangioma, branchial cyst, trichilemmal
cyst, lymphadenopathy, sebaceous cyst, subperiosteal abscess, or hematoma.
Histochemical examination of hair has shown that in the trichilemmal
sac encircling hair the germinal cells rich in free thiol groups are abundant, and disulphide bonds limit themselves (24).
cyst and epidermal cyst represent a big portion of tumoral lesions that cause a subcutaneous nodule in the scalp.
In addition, 6 control biopsies were taken from healthy subjects undergoing surgeries for a trichilemmal
cyst or plastic surgery.
(4,121) In addition, BCC with extensive clear cell changes may raise consideration for trichilemmal
carcinoma, clear cell melanoma, and other clear cell tumors presenting in the skin.
Arata, "Expression of keratins (K10 and K17) in steatocystoma multiplex, eruptive vellus hair cysts, and epidermoid and trichilemmal
cysts," The American Journal of Dermatopathology, vol.
Apart from these three, three more entities which are filled with keratinous debris can occur in the body, namely, teratoma, keratinous cyst, and trichilemmal
observed that pilomatricoma was the most common benign tumor followed by dermoid cyst followed by steatocystoma multiplex, syringoma, and trichilemmal
The differential diagnosis of PC includes basal cell carcinoma, squamous cell carcinoma, epidermoid cyst, foreign-body granuloma, multiple osteomas of the skin, osteochondroma, parotid tumor, proliferating trichilemmal
cyst, and other entities.
Eruptive Vellus Dermal cysts lined by stratified squamous Hair Cysts epithelium, with granular layer, contained vellus hairs; no sebaceous glands  Epidermoid cysts Cysts lined by stratified epithelium, with granular layer, lamellar keratin inside  Milia Small cysts in the superficial dermis coated by epithelium with granular cell layer' contains lamellar keratin  Trichilemmal
cysts Cysts lined by squamous epithelium without granular layer, filled with homogenous keratin  Steatocystomas Cysts lined by stratified squamous epithelium without granular layer and vellus hairs inside the cavity; sebaceous lobules close to the cystic wall 
Malignant cutaneous neoplasms are less commonly seen and include basal cell carcinoma and to a lesser extent squamous cell carcinoma trichilemmal
carcinoma sebaceous carcinoma porocarcinoma and apocrine carcinoma.4