Sebaceous glands are composed of holocrine acini attached to a common excretory duct and a follicle, and together they comprise the pilosebaceous unit. In SGH, the sebaceous glands are normal in structure but increased in number [6]. Since all the acini are attached to the central duct, which may become dilated, as well as the follicular infundibulum, when the sebaceous glands increased. In our study, a dilated central follicular infundibulum containing medium and high refraction structures were present in 15 cases (48.39%) under RCM examination, correlating with the central umbilication noted by dermoscopy in 19 cases (61.29%). As Neda et al [7]. reported, the dilated central duct and follicular infundibulum contained sebum and keratin debris, so the feature of umbilication in SGH observed by dermoscopy is different from molluscum contagiosum. In molluscum contagiosum, the umbilication corresponds to molluscum bodies, which show round, well-circumscribed lesion with a central round cystic area filled with brightly refractile material in RCM [8].
This study showed that white-yellowish lobulated structures were the most common dermoscopic features in SGH, corresponding to the morulae-shaped sebaceous lobules observed under RCM. Bryden and colleagues [9] named it as a "cumulus sign", which can be easily distinguished from the blue gray ovoid nest in base cell carcinoma under dermoscopy. Moreover, the presence of morulae-shaped structure in SGH compare to bright tumor islands observed in base cell carcinoma and trichoepithelioma indicates its value as a distinguishing feature. Additionally, morulae-shaped structure has also been described in sebaceous nevus, further identification is needed in clinical manifestation and histopathological examination.
Regarding vascular structures we found irregular linear vessels (58.06%) were the most common vessel type in SGH, followed by crown vessels (35.48%). This is different from the findings of Argenziano and Oztas [10, 11] that crown vessels were the most common vascular pattern. Arborizing vessels were observed in 2 (6.45%) cases, identification of non-pigmented base cell carcinoma through other structures or RCM examination is required. The different vascular pattern in dermoscopic presented as dark dilated vessels in RCM, that were observed in 26 (83.87%) cases. In dermoscopic analysis of our study, monomorphic vessel pattern was mainly perceived, while Chun-Yu Cheng et al. [12] reported that the polymorphic vessel pattern often indicates the malignant tumor, such as sebaceous carcinoma.
In 13 cases (41.94%) sebaceous lobules surrounded by hyper-refractile cytoplasm were noticed, this finding is also supported by Fraga-Braghiroli et al. [13] Notably, the surrounding dermis showed amorphous bright, broadened and reticulated collagen fibers compatible with solar elastosis. This is not rare in patients with SGH.
In summary, we have examined SGH by dermoscopy and RCM and correlated them with corresponding histopathological findings. There are mainly three dermoscopic and RCM features noticeable in SGH, which are helpful for diagnosis and differential diagnosis: (i) white-yellowish lobulated structures in faintyellow or yellowish red background, corresponds to the morulae-shaped sebaceous lobules in RCM; (ii) umbilication in the center of the lesion, corresponds to dilated follicular infundibulum in RCM; (iii) crown or linear-irregular vessels, corresponds to dark dilated vessels in RCM. The main limitation of our study is the relatively small number of patients. Secondly, we only selected the lesions on the face. Further studies with large samples are needed to test our findings and explore the usefulness of dermoscopy and RCM as a non-invasive diagnostic tool in SGH.
Table 1
Clinic characteristics of the patient's group
Gender | n(%) |
Female | 26(83.87) |
Male | 5(16.13) |
Age(years) | Mean(rang) |
Female | 51 ± 16.99(23–68) |
Male | 54.85 ± 12.23(30–75) |
Duration(months) | |
Female | 20.6 ± 8.99(13–36) |
Male | 22 ± 16.42(4–72) |
Size(mm) | |
Female | 6.92 ± 2.40(4.3–10) |
Male | 6.03 ± 1.45(3.6–8.3) |
Table 2
Dermoscopic and RCM characteristics of SGH
| n(%) |
Dermoscopic feature | |
Faintyellow background | 6(19.35) |
Yellowish red background | 25(80.65) |
White-yellowish lobulated structure | 31(100) |
Umbilication | 19(61.29) |
Crown vessel | 11(35.48) |
Irregular linear vessel | 18(58.06) |
Arborizing vessel | 2(6.45) |
Scale | 3(9.68) |
RCM feature in epidermis | |
Honeycombed pattern | 31(100) |
Streaming in epidermis | 4(12.90) |
Dilated follicular infundibulum | 15(48.39) |
Morulae-shaped sebaceous lobules | 31(100) |
Dilated vessels | 26(83.87) |
Inflammatory cells in superficial dermis | 2(6.45) |
Sebaceous lobules surrounded by hyper-refractile cytoplasm | 13(41.94) |
RCM reflectance confocal microscopy, SGH sebaceous gland hyperplasia |