Dermatology: Practical and Conceptual Research Letter | Dermatol Pract Concept. 2024;14(1):e2024014 1 Lingual Epidermal Choristoma: Ultrasonography as a Diagnostic Tool Constanza del Puerto1, Ximena Wortsman2,3, Camila Downey1,4 1 Department of Dermatology, Clínica Alemana de Santiago, Santiago, Chile 2 Institute for Diagnostic Imaging and Research of the Skin and Soft Tissues Clinic, Santiago, Chile 3 Department of Dermatology, School of Medicine, Pontificia Universidad Católica de Chile, Santiago, Chile 4 Department of Dermatology, Hospital Luis Calvo Mackenna, Santiago, Chile Key words: choristoma, ultrasonography, mucous membrane disorders, pigmentary disorders Citation: del Puerto C, Wortsman X, Downey C. Lingual Epidermal Choristoma: Ultrasonography as a Diagnostic Tool. Dermatol Pract Concept. 2024;14(1):e2024014. DOI: https://doi.org/10.5826/dpc.1401a14 Accepted: May 31, 2023; Published: January 2024 Copyright: ©2024 del Puerto et al. 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: All authors have contributed significantly to this publication. Corresponding Author: Constanza del Puerto, Department of Dermatology, Clínica Alemana de Santiago, Santiago, Chile. 5951 Vitacura Avenue, Santiago, Chile. Email address: conidelpuerto@gmail.com Introduction Choristoma is a rare benign congenital malformation consisting of normal growth of cells or tissue that is foreign to that body site [1]. Epidermal choristoma (EC) is ectopic epidermal tissue. It is a rare benign lesion on the tongue that presents as solitary or multiple brown macules or papules [2]. Recent publications suggest clinical follow-up considering its benign course [2]. We report a patient with an EC with a 5-year follow-up and whose diagnosis was supported by high-definition ultrasonography. Case Presentation A healthy 2-month-old boy consulted for three light-brown homogeneous macules on the right dorsal aspect of the tongue (Figure 1A). Congenital oral melanotic macules and epidermal choristoma were included in the differential di- agnosis. After discussing management alternatives with the patient family, clinical observation was chosen. The macules grew proportionally to the child’s development, becoming palpable and with surface changes at age of five (Figure 1B). High frequency and ultra-high frequency color Doppler ul- trasound demonstrated submucosal thickening with multi- ple hypoechogenic oval structures, consistent with sebaceous glands, without hypervascularity (Figure 2, A-C). The find- ings were consistent with lingual EC. Conclusions The presence of sebaceous glands in the oral mucosa is not uncommon, but on the tongue is exceptional and is consid- ered an EC [3]. Most cases present on the tongue in males before the age of 2 [2]. It is clinically characterized by one or multiple macules or papules unilaterally or in the mid- line dorsal tongue. Color varies from light to dark brown; therefore, it is usually misdiagnosed as a congenital mela- notic macule [1,2]. The histopathological study shows the 2 Research Letter | Dermatol Pract Concept. 2024;14(1):e2024014 replacement of normal oral mucosal epithelium by strat- ified squamous epithelium, hyperkeratosis, pigmentation of the basal layer, abortive hair follicles, and sebaceous glands [1]. In the case of congenital exclusively lingual pigmenta- tion, most relevant differential diagnoses are congenital lin- gual melanotic macule (CLMM) and EC. Clinical clues to differentiate EC from CLMM are that EC usually becomes a palpable lesion over time, whereas CLMM usually presents as highly pigmented macules in dark skinned patients [4]. High and ultra-high frequency color Doppler ultrasound have gained relevance in skin and mucosal conditions and can be useful in children where an oral cavity biopsy proce- dure is complex. The axial spatial resolution of ultra-high fre- quency ultrasound at 70 MHz goes up to 30 microns, closer to the lower magnification of histology. The ultrasound pattern of sebaceous glands has been reported previously as oval-shaped hyperechoic structures that may be or are not attached to the hair follicles, as our case (Figure 2, A-C) [5]. The gold standard for the diagnosis of EC is histopathol- ogy. However, a tongue biopsy in a child usually requires sedation, with all the risks it implies, including 0.4%-17% [6] of acute complications and yet unknown long-term neuro- logical side effects. For this reason, we propose that ultra- sound and particularly ultra-high frequency ultrasound, may be an alternative for the diagnosis and monitoring of EC in cases where families and physicians decide to perform active clinical observation, especially considering that oral congeni- tal melanoma has not been reported yet, the difficulty of oral biopsy in a neonate and that sedation under three years of age may carry risks. References 1. Curto-Barredo L, Vicente A, Rovira C, Garcia-Diez E, Pujol RM, Gonzalez-Ensenat MA. Epidermal Choristoma of the Tongue Mimicking a Congenital Melanotic Macule. Pediatr Derma- tol. 2015;32(4):536-538. DOI:  10.1111/pde.12487. PMID: 25529319. 2. Hughes C, Ferro A, Dubb S, et al. Epidermal choristoma: a case series and review of the literature. Pediatr Dermatol. 2021;38(5):1243-1246. DOI:  10.1111/pde.14589. PMID: 34338332. Figure 1. (A,B) (A) Three light-brown homogeneous macules on the dorsum of the tongue when the patient was 2 months old. (B) At the age of 5, 3 light-brown homogeneous now palpable lesions on the right dorsum of the tongue. Figure 2. (A-C) Ultrasound at 70 MHz (Vevo MD; Visualsonics Fujifilm) of the tongue (transverse views) demonstrates multiple sebaceous glands as hyperechoic oval-shaped submucosal structures on the right side of the tongue (A) that were delineated with a white color (B). Notice the difference with the left side of the tongue (C) that does not present sebaceous glands. Research Letter | Dermatol Pract Concept. 2024;14(1):e2024014 3 3. Azorin D, Enriquez de Salamanca J, de Prada I, Colmenero I, Gonzalez Mediero I. Congenital melanotic macules and Se- baceous Choristoma arising on the tongue of a newborn: epi- dermal choristoma? J Cutan Pathol. 2005;32(3):251-253. DOI: 10.1111/j.0303-6987.2005.00325.x. PMID: 15701089. 4. Resende NM, Vasques Bittencourt F, Gontijo B. Congenital Melanotic Macule of the Tongue: A Five-Year Follow-Up. Dermatol Pract Concept. 2021;11(4):e2021122. DOI: 10.5826 /dpc.1104a122. PMID: 35024231. PMCID: PMC8648429. 5. Wortsman X, Carreno L, Ferreira-Wortsman C, et al. Ultrasound Characteristics of the Hair Follicles and Tracts, Sebaceous Glands, Montgomery Glands, Apocrine Glands, and Arrector Pili Mus- cles. J Ultrasound Med. 2019;38(8):1995-2004. DOI:  10.1002 /jum.14888. PMID: 30570163. 6. Dong SZ, Zhu M, Bulas D. Techniques for minimizing sedation in pediatric MRI. J Magn Reson Imaging. 2019;50(4):1047- 1054. DOI: 10.1002/jmri.26703. PMID: 30869831.