Asploro Journal of Biomedical and Clinical Case Reports
ISSN: 2582-0370
Article Type: Case Report
DOI: 10.36502/2023/ASJBCCR.6300
Asp Biomed Clin Case Rep. 2023 Jun 05;6(2):103-105

Proliferating Trichelemmal Cyst of Extra Cephalic Location

Sabrina Oujdi1*, Hanane Baybay1, Siham Boularbah1, Sara Elloudi1, Meryem Soughi1, Zakia Douhi1, Fatima Zahra Mernissi1
1Department of Dermatology, University Hospital Hassan II, Fes, Morocco

Corresponding Author: Sabrina Oujdi
Address: Department of Dermatology, University Hospital Hassan II, Fes, Morocco.
Received date: 19 April 2023; Accepted date: 29 May 2023; Published date: 05 June 2023

Citation: Oujdi S, Baybay H, Boularbah S, Elloudi S, Soughi M, Douhi Z, Mernissi FZ. Proliferating Trichelemmal Cyst of Extra Cephalic Location. Asp Biomed Clin Case Rep. 2023 Jun 05;6(2):103-105.

Copyright © 2023 Oujdi S, Baybay H, Boularbah S, Elloudi S, Soughi M, Douhi Z, Mernissi FZ. This is an open-access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium provided the original work is properly cited.

Keywords: Benign Proliferating Trichilemmal Cyst, Adnexal Tumor, Scalp, Extracephalic, Benign Behavior, Infiltrating Forms, Local Recurrence, Histologically Transformed Forms, Metastasis, Lymph Nodes, Differentiation


The trichilemmal proliferating cyst is a member of the group of adnexal tumors arising from the hair follicle, more specifically from the isthmic trichilemmal segment of the external epithelial sheath of the hair follicle. It is most often located on the head and neck, but case reports of extracephalic localization are described in the literature. We report a case of a proliferating trichilemmal cyst on the back, where the diagnosis was made after the anatomopathological study of the excised specimen.


Cutaneous adnexal tumors are rare and heterogeneous primary tumors of the skin. They originate from the epithelial structures of the adnexa, including the pilosebaceous unit, sweat glands (eccrine and apocrine), and sebaceous glands. The clinical appearance of these tumors is non-specific and can be misleading, making the diagnosis often reliant on anatomopathological examination. These tumors are characterized by a wide range of morphological variations and lesion polymorphism.


A 40-year-old female patient with no previous medical history presented with a progressively enlarging nodule on her back that had been present for 14 years. The patient occasionally experienced itching and attempted to manipulate the nodule using a sewing needle. Upon clinical examination, a 3 cm long erythematous nodule with a sessile base was observed on the back (refer to Fig-1). Dermoscopy revealed an erythematous background, telangiectasias, arborescent vessels, and a homogeneous blue-gray area (refer to Fig-2). The rest of the clinical examination did not reveal any notable findings.

Fig-1: Erythematous Nodule with A Sessile Base on the Back
Proliferating Trichelemmal Cyst of Extra Cephalic Location
Proliferating Trichelemmal Cyst of Extra Cephalic Location
Dermoscopy Showing an Erythematous Background, Telangiectasias, Arborescent Vessels and A Homogeneous Blue-Gray Area

Based on the clinical presentation, the differential diagnoses considered were pilomatricoma, nodular hidradenoma, and centrofollicular B-cell lymphoma. However, an excisional biopsy confirmed a diagnosis of a proliferating trichilemmal cyst.


Proliferating trichilemmal cyst (PTC), also known as proliferating trichilemmal tumor, is a rare tumor that was initially described by Wilson Jones in 1966 as an epidermoid cyst [1]. It is a slow-growing tumor that arises from the isthmic trichilemmal segment of the external epithelial sheath of the hair follicle. PTC predominantly affects women over the age of 50. The exact cause of this tumor is unknown, but it has been suggested that it represents a proliferation within a pre-existing trichilemmal cyst, often triggered by trauma or chronic inflammation [2].

Although the most common location for PTC is the scalp, it can also occur in other areas such as the extremities, back (as in the case of the patient described), and the pubic and vulvar regions [3]. There are two types of PTC: benign and malignant. Malignant PTC has the potential to undergo malignant transformation and metastasize, particularly to the lymph nodes. Clinically, PTC presents as a firm, nodular swelling with a smooth surface, ranging in diameter from 2 to 15 cm. The proliferative nature of the tumor may be evident from the beginning or can develop as a result of repeated trauma. Differential diagnoses based on clinical appearance may include pilomatricoma, keratoacanthoma, and squamous cell carcinoma.

Histologically, PTC is characterized by a central intracystic proliferation with masses and trabeculae of epithelial cells replacing the cyst lumen. Trichilemmal keratinization is observed, characterized by compact, non-nucleated masses. Invasive masses and trabeculae extend into the surrounding tissues, displaying nuclear polymorphism, cytonuclear atypia, and occasionally atypical mitoses, resembling squamous cell carcinoma. However, trichilemmal differentiation and keratinization are consistently observed in the central part of the masses, without a granular layer, and trichilemmal cystic areas may still persist [4].

The criteria associated with malignancy, as described by Folpe et al., include location outside the scalp, rapid growth, size larger than 5 cm, infiltrative architecture, marked cytologic atypia, and numerous mitoses [5].

The management of proliferating trichilemmal cysts typically involves surgical excision with adequate safety margins (approximately 1 cm). In cases of malignant forms, effective chemo-radiotherapy may be employed in addition to surgery, and radiotherapy can be used as adjuvant therapy to reduce the risk of recurrence [6].


The benign proliferating trichilemmal cyst is an adnexal tumor that primarily occurs in the scalp and infrequently in extracephalic locations. This tumor generally exhibits a benign behavior, with infiltrating forms having a low risk of local recurrence. Histologically transformed forms with a low risk of metastasis, particularly in the lymph nodes, also exist. However, distinguishing between these various forms histologically can be challenging.

Conflict of Interest

The authors have read and approved the final version of the manuscript. The authors have no conflicts of interest to declare.


[1] Jones EW. Proliferating epidermoid cysts. Arch Dermatol. 1966 Jul;94(1):11-19. [PMID: 5938217]

[2] Markal N, Kurtay A, Velidedeoğlu H, Hücümenoğlu S. Malignant transformation of a giant proliferating trichilemmal tumor of the scalp: patient report and literature review. Ann Plast Surg. 1998 Sep;41(3):314-16. [PMID: 9746092]

[3] López-Ríos F, Rodríguez-Peralto JL, Aguilar A, Hernández L, Gallego M. Proliferating trichilemmal cyst with focal invasion: report of a case and a review of the literature. Am J Dermatopathol. 2000 Apr;22(2):183-87. [PMID: 10770443]

[4] Joshi TP, Marchand S, Tschen J. Malignant Proliferating Trichilemmal Tumor: A Subtle Presentation in an African American Woman and Review of Immunohistochemical Markers for This Rare Condition. Cureus. 2021 Aug 18;13(8):e17289. [PMID: 34552829]

[5] Folpe AL, Reisenauer AK, Mentzel T, Rütten A, Solomon AR. Proliferating trichilemmal tumors: clinicopathologic evaluation is a guide to biologic behavior. J Cutan Pathol. 2003 Sep;30(8):492-98. [PMID: 12950500]

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