Dermatology: Practical and Conceptual Dermatology Practical & Conceptual Research Letter | Dermatol Pract Concept. 2022;12(1):e2022026 1 Trichofolliculoma Mimicking Squamous Cell Carcinoma Ahmed Abdelbary1, Hadir Shakshouk1 1 Department of Dermatology, Andrology and Venerology, Alexandria University, Egypt Key words: trichofolliculoma, adnexal tumors, hamartoma, dermoscopy, case report Citation: Abdelbary A, Shakshouk H. Trichofolliculoma mimicking squamous cell carcinoma. Dermatol Pract Concept. 2022;12(1):e2022026. DOI: https://doi.org/10.5826/dpc.1201a26 Accepted: June 6, 2021; Published: January 2022 Copyright: ©2022 Abdelbary and Shakshouk. This is an open-access article distributed under the terms of the Creative Commons Attribution-NonCommercial License (BY-NC-4.0), https://creativecommons.org/licenses/by-nc/4.0/, which permits unrestricted noncommercial use, distribution, and reproduction in any medium, provided the original authors and source are credited. Funding: None. Competing interests: None. Authorship: Both authors have contributed significantly to this publication. Corresponding author: Hadir Shakshouk, MBBS, MSc, Department of Dermatology, Andrology and Venerology, Alexandria University, Egypt. E-mail: drhadir58@gmail.com Introduction Trichofolliculoma, a rare follicular hamartoma, manifests it- self as a solitary papule or nodule in adults involving the head and neck region. It is characterized by a single primary cystic structure from which radiates numerous secondary hair folli- cles. While dermoscopy has been widely used as a diagnostic tool, dermoscopic features of adnexal lesions are poorly de- scribed owing to their rarity and inadequate reporting. Case Presentation We describe a 75-year-old male patient who presented with asymptomatic solitary nodule on the forehead of 2-years du- ration. Upon examination, a single nodule of 1 cm diameter with central crust and raised border was noted on his fore- head (Figure 1A). Dermoscopic evaluation revealed a nodule with central crusting, multiple fine linear vessels, and whitish circles mainly on the margin (Figure 1B). These features were highly suggestive of squamous cell carcinoma. However, histopathological examination demon- strated multiple cystically dilated follicular infundibula lined by stratified squamous epithelium with numerous vellus hair follicles originating from them. Multiple lobules of follicles of varying maturity were observed radiating from these dilated follicular infundibula. Some showed sebaceous glands. A fibro- cellular stroma surrounding the tumor was noted (Figure 1C). Thus, a diagnosis of trichofolliculoma was made. Written informed consent for publication of clinical de- tails and clinical images was obtained from the patient. Conclusions Trichofolliculoma is considered to be a rare follicular ham- artoma that classically manifests as a papule or nodule with a central dilated pore and tufted hairs. This presen- tation corresponds histopathologically to a central primary follicle with many radiating secondary vellus hair follicles. 2 Research Letter | Dermatol Pract Concept. 2022;12(1):e2022026 While thought to be diagnostic for trichofolliculoma, few cases demonstrate central hair tufting. The lack of a cen- tral hair plug, as in our case, renders the clinical diagnosis challenging. Dermoscopy of trichofolliculoma is not well described in literature. Panasiti et al reported a patient with single nod- ule suspicious for basal cell carcinoma [1]. However, der- moscopic examination revealed a central brown zone with radial brown projections without pigment network, which was described by the authors as a “firework” pattern. These projections correlated histopathologically with the nests of cells radiating from a follicular epithelium [1]. Garcia-Gar- cia and colleagues described different dermoscopic features that included a well-defined bluish nodule with a white- pink central area, shiny white structures, dotted vessels, and a central scale in one patient [2]. Histopathologically, the early stages demonstrated few secondary vellus hair follicles originating from a primary follicle, whereas mature lesions showed increased number of vellus hair follicles. In later stages, thickened primary follicle with fewer secondary folli- cles could be seen [2]. Trichofolliculoma classically presents with a hair plug emanating from the center of a nodule; however, hair plug may be absent in many cases, making the diagnosis challeng- ing. In these cases, other serious diagnoses should be ruled out. Dermoscopy of trichofolliculoma is poorly described in the literature. We introduce the possibility of new dermo- scopic findings of trichofolliculoma. References 1. Panasiti V, Roberti V, Lieto P, Visconti B, Calvieri S, Perrella E. The “firework” pattern in dermoscopy. Int J Dermatol. 2013;52(9):1158- 1159. DOI: 10.1111/j.1365-4632.2011.05122.x. PMID: 22591242. 2. Garcia-Garcia SC, Villarreal-Martinez A, Guerrero-Gonzalez GA, Miranda-Maldonado I, Ocampo-Candiani J. Dermoscopy of trichofolliculoma: a rare hair follicle hamartoma. J Eur Acad Dermatology Venereol. 2017;31(2):e123-e124. DOI: 10.1111/ jdv.13870. PMID: 27504964. Figure 1. (A) Clinical examination showed a well-defined nodule with central crust on the forehead. (B) Dermoscopic evaluation showed a nodule with central crusting, multiple fine linear vessels, and whitish circles mainly on the margin. (C) Histopatho- logic examination showed dilated primary follicular infundibula with numerous sec- ondary hair follicles, and a few showed sebaceous glands. A fibrocellular stroma surrounding the tumor was noted (H&E, original magnification ×20).