The sonographic and histopathologic correlation study of solitary nevus lipomatosus cutaneus superficialis

Sir,

Nevus lipomatosus cutaneus superficialis (NLCS) is a rare type of connective tissue nevus, first described in 1921 by Hoffman and Zurhelle.¹ It has been classified into two clinical types: multiple (classic) and solitary. The classic type is characterised by papules or plaques commonly located on the lower back, buttocks and thighs. The solitary type usually presents with a solitary nodule or papule. There are only limited studies describing the image features of this condition and no study investigating the ultrasonographic characteristics.² Therefore, we conducted the present study to analyse the sonographic and histopathologic correlation of this entity.

In the present study, we collected four cases of histopathology confirmed nevus lipomatosus cutaneus superficialis at Chang Gung Memorial Hospital, Taoyuan branch, from 1^st January 2020 through 31^st May 2021. All the sonographic examination was performed by one dermatologist (C.Y.C.) using Acuson ×150TM ultrasound system (Siemens Medical Solutions USA, Mountain View, CA). Digital images were reviewed by two of the authors (C.Y.C. and Y.W.T.), and the sonographic features were confirmed only if the two evaluators reached a consensus.

All four cases were women with a mean age of 60 ± 6.4 (51–69) years. The affected areas included thighs (n = 3, 75%) and back (n = 1, 25%) and the mean size was 10 ± 2.8 (range: 8.0–14.8) mm. All cases were solitary type of nevus lipomatosus cutaneus superficialis [Figures 1a–d]. The characteristics of sonographic findings were demonstrated in [Figures 1e–h]. In the ultrasonographic examination, all tumours were located in the dermis to subcutis and exhibited heterogeneous texture and ovoid shape. [Table 1] Most cases were isoechoic (n = 3, 75%), while one case was hyperechoic. Focal hypoechoic areas and posterior acoustic shadows were seen in all cases. The histopathological features were characterized by the proliferation of ectopic mature adipocytes with the thickening of collagen bundles in the dermis. [Figures 1i–l].

Close

Figures 1:

(a) A skin colored nodule on the back of case 1; (b) A skin colored nodule on the right thigh of case 2; (c) A skin colored nodule on the right thigh of case 3; (d) A skin colored nodule on the left thigh of case 4

Export to PPT

Close

Figures 1e-h:

Ultrasonography of case 1–3 showed a heterogeneous isoechoic mass with the focal hypoechoic area (white arrowheads) and posterior acoustic shadow [Ultrasound frequency: 11.4 MHz]. Ultrasonography of case 4 showed a hyperechoic lesion with the central hypoechoic area (white arrowhead) and posterior acoustic shadow [Ultrasound frequency: 11.4 MHz]

Export to PPT

Close

Figures 1i-l:

The histopathology of case 1–3 revealed characteristic proliferation of ectopic mature adipocytes with thickening of collagen bundles present in the dermis [H and E ×20]. The histopathology of case 4 revealed closely packed adipocytes intermingled with collagen bundles [H and E, ×40]

Export to PPT

The present study demonstrated that the ultrasonographic features of nevus lipomatosus cutaneus superficialis were mainly heterogeneous isoechoic ovoid shape with focal hypoechoic area and posterior acoustic shadow. We suppose that adipose tissue interposed into the dermis and intermingled with collagen bundles results in heterogeneity in sonography. The isoechoic structure was the dilated collagen bundles caused by the interspersion of adipocytes, while the hypoechoic area was the adipose tissue within the tumour. Additionally, the acoustic impedance of the dermis is higher than fatty tissue. Therefore, when the ultrasonic wave re-enters from the adipose tissue of the nevus into the dermis, some of the acoustic energy may reflect and the transmission is reduced, resulting in acoustic shadow.

Clinically, solitary nevus lipomatosus cutaneus superficialis should be differentiated from lipoma, neurofibroma, angioleiomyoma, neuroma and dermatofibroma. Ultrasonography can be applied to differentiate from these tumours. Lipoma and angioleiomyoma are mostly located in subcutis, while this is mainly located in the dermis.² In addition, the sonographic features of angioleiomyoma are mainly homogeneous hypoechoic lesion with protrusions on one or both ends along with posterior acoustic enhancement.² Neurofibroma is mostly a homogenous hypoechoic lesion without posterior acoustic shadow, whereas this nevus is a heterogeneous isoechoic lesion with posterior acoustic shadow.³ Neuroma and dermatofibroma are hypoechoic lesions in the dermis.^4,5

In conclusion, we demonstrated the sonographic features of nevus lipomatosus cutaneus superficialis and analysed the sonographic and histopathologic correlation. Sonography is a noninvasive and real-time diagnostic tool, valuable in assisting the diagnosis of nevus lipomatosus cutaneus superficialis.