Proliferating trichilemmal cysts are dermal or subcutaneous tumors with squamoid cytologic features and trichilemmal-type keratinisation usually arising in the scalp.
A variety of names have been used for this pathology, including proliferating epidermoid cyst, pilar tumor of the scalp, proliferating trichilemmal cyst, proliferating epidermoid cyst, giant hair matrix tumor, hydatidiform keratinous cyst, trichochlamydocarcinoma, and invasive hair matrix tumor 1.
Proliferating trichilemmal cysts have female predominance 3,4.
Proliferating trichilemmal cysts present as lobulated masses within the scalp. They vary considerably in size from a few millimeters to large masses many centimeters in diameter. Occasionally clinical presentation will be with superimposed infection or malignant transformation, although both of these complications are uncommon 3.
Although they are mostly benign, they have local invasive and malignant types 2. They show extensive epithelial proliferation, variable cytologic atypia and mitotic activity.
Proliferating trichilemmal cysts usually are located within the scalp and appear as multiple complex subcutaneous solid or cystic masses. The cystic components contain high-density proteinaceous material which sometimes layers dependently 3. Ring-like patterns of mineralisation are also encountered 3.
History and etymology
Proliferating trichilemmal cysts were first defined by Edward Wilson Jones, an English dermatopathologist, in 1966 2.
In some situations, consider an epidermal inclusion cyst
- 1. Ye J, Nappi O, Swanson PE, Patterson JW, Wick MR. Proliferating pilar tumors: a clinicopathologic study of 76 cases with a proposal for definition of benign and malignant variants. American journal of clinical pathology. 122 (4): 566-74. doi:10.1309/21DK-LY2R-94H1-92NK - Pubmed
- 2. Jones EW. Proliferating epidermoid cysts. (1966) Archives of dermatology. 94 (1): 11-9. Pubmed
- 3. Chang SJ, Sims J, Murtagh FR, McCaffrey JC, Messina JL. Proliferating trichilemmal cysts of the scalp on CT. (2016) AJNR. American journal of neuroradiology. 27 (3): 712-4. Pubmed
- 4. Sau P, Graham JH, Helwig EB. Proliferating epithelial cysts. Clinicopathological analysis of 96 cases. (2004) Journal of cutaneous pathology. 22 (5): 394-406. Pubmed