Proliferating trichilemmal cysts, sometimes known as proliferating trichilemmal tumors, are dermal or subcutaneous tumors with squamoid cytologic features and trichilemmal-type keratinization, which usually arise in the scalp.
A variety of names have been used for this pathology, including proliferating epidermoid cyst, pilar tumor of the scalp, 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.
Some cases have a syndromic association:
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, there are also local invasive and malignant types 2. The latter 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 mineralization are also encountered 3.
History and etymology
Proliferating trichilemmal cysts were first described 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, et al. 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, et al. 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
- 5. Sharma R, Verma P, Yadav P, et al. Proliferating trichilemmal tumor of scalp: benign or malignant, a dilemma. (2012) Journal of cutaneous and aesthetic surgery. 5 (3): 213-5. doi:10.4103/0974-2077.101394 - Pubmed
- 6. Kim HJ, Kim TS, Lee KH, et al. Proliferating Trichilemmal Tumors: CT and MR Imaging Findings in Two Cases, One with Malignant Transformation. (2001) American Journal of Neuroradiology. 22 (1): 180. Pubmed