Mixed tumour of the skin (MTS) is a relatively rare adnexal tumour usually presenting as a slow-growing, painless nodule in the head and neck region, particularly often around the nose, cheek and upper lip.[1, 2] When MTS occurs on the scalp, it may be difficult to clinically differentiate MTS from other tumours, including epidermal cyst, which often develops on the scalp. Although ultrasonography has been utilized broadly as a non-invasive diagnostic tool for skin tumours, to the best of our knowledge, there have been no reported MTS cases with ultrasonographic information including elastographic features in the medical literature. Here, we show the elastographic findings of MTS, which clearly distinguish from epidermal cyst.

A 54-year-old woman was referred to our hospital because of a tumour on the top of her scalp. She had noticed the lesion 6 months before the referral. As clinical manifestations, a well-defined elastic hard subcutaneous tumour of 10 mm in diameter was observed (Fig. 1a). The patient underwent ultrasound scanning with the HI VISION 900 (Hitachi Medical Corporation, Tokyo, Japan). A conventional linear probe with a 5- to 13-MHz transducer was used in all scans, including B-mode, colour Doppler test and elastography. In all elastographic examinations, we used ‘quasi-static strain imaging’, which indicates slight probe compression towards the tumour, in order to estimate elasticity precisely.[3, 4]


Figure 1. Clinical, histological and ultrasound findings. (a) A 10-mm-diameter subcutaneous nodule is seen on the scalp. (b) A subcutaneous nodule is composed of a mucinous area, a cleft or a ductal formation (haematoxylin and eosin stain; original magnification ×20). (c) Histopathology specimens reveal a subcutaneous tumour with an intimate admixture of epithelial–myoepithelial structures within a chondromyxoid and fibrous stroma (haematoxylin and eosin stain; original magnification ×100). (d) Occasional groups of apocrine glands are also present (haematoxylin and eosin stain; original magnification ×400).

Download figure to PowerPoint

Ultrasonography (B-mode) revealed the border to be subglobular, smooth and well circumscribed, the inside of the tumour to be heterogeneous and high-echo, and posterior echo enhancement to be evident (Fig. 2a; red arrowhead).


Figure 2. Ultrasound findings of cases that were diagnosed with epidermal cysts. (a) In this case, the interior portion of the tumour was visualized as red to green by elastography. In B-mode, posterior echo enhancement is evident (red arrow) (blue arrow), and lateral shadow is seen. (b–f) The five cases of epidermal cyst that were confirmed in our hospital are seen as uniformly blue or green inside of the tumour by elastography (yellow arrow). In B-mode, posterior echo enhancement (blue arrow) and lateral shadow is also seen (red arrow).

Download figure to PowerPoint

Colour Doppler test showed the inside and periphery of the tumour to be hypovascular. Ultrasound elastography indicated that the tumour interior was island-shaped, with a soft, elastic cord-like portion (red) (Fig. 2a; white arrowhead) mixed in a background of moderately (green). Histopathology specimens showed a subcutaneous tumour with an intimate admixture of epithelial–myoepithelial structures within a chondromyxoid and fibrous stroma (Fig. 1b,c). Decapitation secretion was occasionally seen in the space (Fig. 1d). No cellular atypia was seen, and only occasional mitoses were found. From these findings, the diagnosis of MTS was made. Retrospectively, the elastic moderate lesion (visualized green in Fig. 2a) demonstrated in elastography may pathologically correspond to closely aggregated myoepithelial cells around the sweat gland. The elastic soft lesion (visualized in yellow to red in Fig. 2a) that was revealed in elastography may be histologically comparable to a broadly mucinous region, empty space and the chondroid portion.

To compare the present case with ordinary epidermal cyst, we presented five images of cases that had already been histologically confirmed as epidermal cyst. Ultrasonography (B-mode) of epidermal cyst revealed the tumour to be well circumscribed, the inside of the tumour to be a heterogeneous high-echoic region, posterior echo enhancement to be evident (Fig. 2b–f; blue arrowhead) and lateral shadow to be seen (Fig. 2b–f; red arrowhead).[5-8] Almost of all these findings of epidermal cysts were extremely similar to the B-mode image of MTS.

On the other hand, elastography of epidermal cysts uniformly visualized the inside of the tumour as blue or green (Fig. 2b–f; yellow arrowhead), finding that were completely different from the MTS image of our own case (Fig. 2a).

In our case, the combination of B-mode and elastographic findings helped us to keep cystic lesion in mind as a differential diagnosis. When similar elastographic findings for MTS of the scalp are accumulated, it may become more easily diagnosable. We should be encouraged to examine skin tumours on the scalp in conjunction with elastography to make better clinical diagnoses.


  1. Top of page
  • 1
    Hirsch P, Helwig EB. Chondroid syringoma. Arch Dermatol 1961; 84: 835847.
  • 2
    Tsoitis G, Brisou B, Destombes P. Mummified cutaneous mixed tumor. Arch Dermatol 1975; 111: 194196.
  • 3
    Gennisson JL, Deffieux T, Fink M et al. Ultrasound elastography: principles and techniques. Diagn Interv Imaging 2013; 94: 487495.
  • 4
    Kirkpatrick SJ, Wang RK, Duncan DD et al. Imaging the mechanical stiffness of skin lesions by in vivo acousto-optical elastography. Opt Express 2006; 14: 97709779.
  • 5
    Chiou HJ, Chou YH, Chiou SY et al. High-resolution ultrasonography in superficial soft tissue tumors. J Med Ultrasound 2007; 15: 152174.
  • 6
    Yamaguchi T, Ojima N, Hayashi M et al. Epidermal cyst of the breast treated by vacuum-assisted biopsy. Int Surg 2007; 98: 6569.
  • 7
    Jung JH, Eom M, Arkoncel FRP et al. Penile epidermal cyst in a patient with augmentation penoplasty. Korean J Urol 2013; 54: 207208.
  • 8
    Yuan WH, Hsu HC, Chou YH et al. Differences in sonographic features of ruptured and unruptured epidermal cysts. J Ultrasound Med 2012; 31: 265272.