Superficial benign skin and subcutaneous lesions ... · Page 2 of 21 Learning objectives To...

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Superficial benign skin and subcutaneous lesionspresenting in the head and neck

Poster No.: C-1006

Congress: ECR 2014

Type: Educational Exhibit

Authors: O. Pearce1, C. Bowles1, A. Spedding1, S. Keohane1, D. Gibson2;1Cosham/UK, 2Portsmouth/UK

Keywords: Ear / Nose / Throat, Soft tissues / Skin, Ultrasound, CT, MR,Diagnostic procedure, Hemangioma, Cysts

DOI: 10.1594/ecr2014/C-1006

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Learning objectives

To recognise the typical imaging characteristics of superficial, benign skin andsubcutaneous related soft tissue lesions presenting in the head and neck.

Background

The annual incidence of all soft tissue tumours is approximately 300 per 100, 000 inthe general population and benign lesions are 100 times more common than malignantones [1]. With the increasing popularity of 'one-stop' neck lump clinics it is important thatbenign lesions are accurately recognised to avoid unnecessary costly investigations ornon-essential surgery.

Ultrasound is usually the first line imaging investigation employed to assess superficialsoft tissue lesions. For many patients a confident diagnosis can be made at this firstencounter and the patient is reassured without further investigation. If there is eitherclinical or radiological diagnostic doubt following ultrasound, then further characterisationcan be performed with either fine needle aspiration cytology, or alternate imagingmethods including computed tomography (CT) and magnetic resonance imaging (MRI).Ultimately some lesions will always require excision for histological confirmation.

The detection of incidental skin and subcutaneous soft tissue lesions is also increasingas the broader use of CT and MRI for alternative indications is escalating. Awareness ofclassical imaging findings allows the radiologist to confidently diagnose the lesion.

In 2002 the World Health Organisation (WHO) published a classification system for allsoft tissue tumours based on their histological characteristics. We have adapted this toapply to benign lesions related to the skin and subcutaneous soft tissues of the headand neck (Table 1).

Images for this section:

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Table 1: Benign lesions related to the skin and subcutaneous soft tissues of the headand neck.

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Findings and procedure details

1. Epidermal lesions

A study of 488 patients from North Jordan demonstrated that the most frequent epidermallesion encountered is the epidermoid cyst (49%), followed by pilar cysts (27%) anddermoid cysts (22%). Region specific subanalysis revealed a marked subsite variation,the most striking being that 96% of scalp cysts were pilar cysts [2].

• Epidermal cysts - These are benign cutaneous or subcutaneous lesionswhich are lined with stratified squamous epithelium and filled with keratindebris. Ultrasound typically reveals a well defined, heterogenouslyhypoechoic lesion at the junction of the dermis and subcutaneous layerwith posterior acoustic enhancement (Figure 1). A study of 46 epidermalcysts demonstrated that 15% show internal (peripheral or central) Dopplerflow although no microvessels were noted on the histopathologic studiesand this presumably represents motion artefact. Ruptured epidermal cystscan result in internal vascularity (70%) secondary to the local irritant effectof leaked keratin [3]. On MRI epidermal cysts are typically high T2 signal,although with variable low T2 components, and demonstrate thin peripheralgadolinium enhancement. Ruptured cysts more commonly show thick orirregular rim enhancement with surrounding inflammation [4].

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Fig. 1: Ultrasound demonstrates a subcutaneous, well defined, hypoechoic lesion withechogenic debris and posterior acoustic enhancement.References: Radiology, Queen Alexandra Hospital - Cosham/UK

• Trichilemmal (Pilar) Cyst - These cysts are lined with cuboidal epidermalepithelium containing keratinous material. They are slow growing, usuallymultiple, smooth, firm and mobile. They mostly occur in the scalp of middleaged women. CT demonstrates a non-enhancing, well defined low densitylesion related to the skin which may contain focal calcification. The cutisand underlying skull vault are intact (Figure 2). T1 weighted MRI reveals thelesion to be isointense to brain parenchyma [5].

Fig. 2: CT depicting an incidental, well defined scalp cyst with a focus of associatedcalcification. The features are of a trichilemmal cyst.References: Radiology, Queen Alexandra Hospital - Cosham/UK

• Dermoid cysts of the head and neck - Derived from both mesoderm andectoderm, and typically containing a keratinising squamous epithelium withdermal derivatives such as hair follicles, sebaceous glands and fibroadiposetissue, dermoid cysts are usually thin walled, heterogenous, unilocularmasses [6]. If there are globules of fat, the characteristic "sac of marbles"may be seen on ultrasound. At CT and MRI the lesions are heterogenousbut classically demonstrate a macroscopic fat component.

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2. Adnexal Tumours

• Cylindroma - Cylindromas are skin appendage tumours most frequentlyfound in the scalp. Histopathologically they are characterized by irregularlyshaped islands of basaloid cells arranged in a "jigsaw puzzle" pattern,surrounded by an eosinophilic hyaline sheath. Cylindromas are typicallysolitary and sporadic but multiple lesions are seen in Brooke-Spieglersyndrome [7]. Although rare, several cases of malignant transformation ofcylindromas have been reported. The appearances of cylindromas are notdescribed in the radiological literature but cross sectional imaging is certainlyrequired if there is concern regarding malignant transformation and deepinfiltration of the tumour.

3. Pilosebaceous Tumours

• Pilomatrixoma - This is a benign skin tumour originating from hair matrixcells. Approximately half of cases are reported in the head and neck, witha preponderance for the parotidomasseteric region. There is a bimodalage distribution with peaks in the first and sixth decades. Ultrasoundreveals a well circumscribed hyperechoic mass with associated macro ormicrocalcification (Figure 3). Fine needle aspiration can be diagnostic [8].CT and MRI studies are not generally indicated.

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Fig. 3: Pilomatrixoma: Well circumscribed hyperechoic mass withassociated calcification resulting in posterior acoustic shadowing.References: Dr Ximena Wortsman. 'Pilomatrixomas: Masters of Disguise?'http://www.ximenawortsman.com Accessed 31st December 2013

4. Adipocytic

Adipocytic tumours constitute the largest group of mesenchymal soft tissue tumours dueto the high prevalence of lipomas and angiolipomas [9].

• Lipoma - These are composed of mature adipocytes with surrounding andintervening connective tissue stroma. They account for approximately 16%of soft tissue tumours, of which 25% occur in the head and neck with themajority occurring in the subcutaneous soft tissues of the posterior neck [1].On ultrasound, lipomas are typically ellipsoid, hyperechoic compared withadjacent fat and compressible without internal vascularity (Figure 4). Fine

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echogenic bands run parallel to the skin surface. On CT and MRI lipomasfollow fat density/signal on all sequences and do not enhance.

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Fig. 4: Two examples of subcutaneous lipomas. These are both elliptical in shapeand of increased echogenicity compared to the adjacent subcutaneous fat. There is nointernal vascularity. Fine needle aspiration is unnecessary.References: Radiology, Queen Alexandra Hospital - Cosham/UK

• Lipoma variants - These variants may include angiolipoma, pleomorphiclipoma, myolipoma and chondroid lipoma. Depending on the constituents,these may have more complex features on imaging, including enhancementand septae, and may be difficult to differentiate from malignant variants [1].

• Hibernoma - This is a rare tumour of brown fat origin which usually presentswith a slow growing and painless mass, but is capable of compressingadjacent structures. A case series published in 2012 describes the typicalimaging manifestations [10]. Ultrasound demonstrates hyperechoic,circumscribed lesions with hypervascularity. Further evaluation with CToften reveals a mass which is mildly hyperdense compared to subcutaneousfat with mild background enhancement and possible intralesional vessels.The typical MRI features include minimally heterogenous lesions, slightlyhypointense to subcutaneous fat on T1 weighted images that fail to fullysuppress with fat saturation techniques. Enhancement and prominentvasculature may be seen following contrast. Due to the brown fat origin ofthese tumours, they are highly PET avid despite their benignity.

5. Fibroblastic, Myofibroblastic and Fibrohistiocytic

Fibroblastic, myofibroblastic and fibrohistiocytic lesions constitute a large group ofmesenchymal tumours that demonstrate a spectrum of behaviours.

• Nodular fasciitis - A mass-forming, rapidly growing fibrous proliferationusually found in the deep subcutaneous tissue adjacent to the underlyingfascia. Occurring at any age, but with a predilection for young adults,approximately 20% of cases are found in the head and neck [9]. Ultrasoundtends to show non-specific well defined hypoechoic lesions with mild internalvascularity. With CT, the well defined subcutaneous lesions are of soft tissuedensity with varying degrees of enhancement (Figure 5). Cystic spaces maybe seen. Findings on MRI are less consistent given the variable cellularity.Highly cellular subtypes have a T2 signal higher than adjacent muscle butmore fibrous lesions show decreased signal across all pulse sequences [11].Although outside the scope of this exhibit, deeper intramuscular lesions canoccur and these may exhibit more aggressive imaging features includingpoor definition and bony erosion.

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Fig. 5: This patient presented with a previously rapidly growing lesion over the leftcheek which had recently stopped growing. Right: On ultrasound the lesion is welldefined and hypoechoic. Left: CT reveals a well defined, homogenous, enhancing softtissue density lesion. Excision biopsy diagnosed nodular fasciitis.References: Radiology, Queen Alexandra Hospital - Cosham/UK

• Deep Benign Fibrous Histiocytoma - These are tumours containingfibroblastic and histiocytic elements arising from the subcutaneous softtissues. They are rare lesions accounting for less than 1% of histiocytictumours [1]. The imaging findings are not well reported but they arepredominantly enhancing solid lesions (Figure 6). There is a quoted 1%malignant transformation rate with no reliable distinguishing imagingfeatures reported. Histologically, malignant lesions have prominent areas ofnecrosis and haemorrhage [12]. It would seem plausible that these featurescould be identified using MRI.

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Fig. 6: There is homogenous enhancement of this subcutaneous right cheek lesionwhich is well defined. Histology confirmed a deep benign fibrous histiocytoma.References: CE Skoulakis et al. Subcutaneous benign fibrous histiocytoma of thecheek. Case report and review of the literature. Acta Otorhinolaryngol Ital. 2007 April;27(2): 90-93.

6. Arteriovenous

• Haemangioma - Common tumours usually arising within the first monthof life, and growing throughout the first year. Consist of hamartomatouscapillary proliferation. Ultrasound shows high flow vascular lesions, withsmall vessels set in a fibro-fatty matrix (Figure 7). Involution occurs usuallyover the first decade, with expansion of the underlying matrix [13]. Extensiveflat facial lesions can be associated with a variety of intracranial anomalies,and MR imaging should be considered. Adult onset 'haemangiomas' areoften in fact venous malformations.

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Fig. 7: Solid subcutaneous tumour with disorganised high vascular flow in keepingwith a haemangioma.References: Radiology, Queen Alexandra Hospital - Cosham/UK

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• Arteriovenous/venous malformation- High flow arteriovenous malformations(AVMs) consist of abnormal connections between arteries and veins withoutan intervening normal capillary bed. Ultrasound shows both abnormalarterial and venous flow, and a feeding arterial supply should be identifiedto guide therapy (Figure 8). MR will show multiple flow voids. Low flowvenous malformations (VMs) consist of dysplastic venous channels withoutarteriovenous shunting. Spectral ultrasound shows low flow in enlargedvascular channels. Phleboliths within a vascular anomaly are characteristicfor VMs [13].

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Fig. 8: High flow AV malformation of the dorsal nose. Mixed arterial and venous flowdemonstrated with a focal venous lake, and feeding arterial supply from the facialartery and dorsal nasal artery.References: Radiology, Queen Alexandra Hospital - Cosham/UK

• Lymphatic malformation- Lymphatic malformations (LMs) are cystic masses,consisting of dysplastic lymphatic channels filled with protein rich fluid. Theyare generally present from birth, but may be silent until complicated by

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infection or haemorrhage. Large LMs may exert considerable mass effect,potentially endangering the airway and causing bony remodelling of thefacial skeleton. MRI is the investigation of choice to confirm the diagnosisand delineate the extent of LMs, which characteristically appear as complexcystic lesions with fluid-fluid levels of varying signal intensity depending onthe co-existence of haemorrhage and protein (Figure 9) [14]. Different cysticlocules can often lie in separate fascial planes.

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Fig. 9: Lymphatic malformation of the neck. Septated, multicystic appearances onultrasound. T1 weight MRI shows fluid-fluid level within a locule, with high T1 signalreturn in keeping with proteinaceous material.References: Radiology, Queen Alexandra Hospital - Cosham/UK

7. Nerve origin

• Schwannoma - Schwannomas are benign encapsulated tumours ofSchwann cells, arising eccentrically from parent nerves of variable size.The encapsulated nature means surgical resection has good successrates with low recurrence [15]. Ultrasound and CT show solid tumours withheterogenous character secondary to internal haemorrhage and necrosis.On MRI, Schwannomas follow fluid signal characteristics, again with internalheterogeneity. There is avid contrast enhancement on all modalities (Figure10).

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Fig. 10: Heterogenous solid subcutaneous tumour on ultrasound. MRI shows an avidlyenhancing lesion within level V, in keeping with a brachial plexus Schwannoma.References: www.radiopaedia.org/cases/schwannoma-brachial-plexus, contributed byDr Frank Gaillard (MRI image)

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• Neurofibroma- Neurofibromas are benign neural based tumours consistingof Schwann cells and fibroblasts within a collagen network. UnlikeSchwannomas, neurofibromas are not encapsulated, and are diffuselyinfiltrative throughout the parent nerve. They are therefore difficult tosurgically resect, with high recurrence rates and neural sacrifice. Mostneurofibromas are solitary lesions, with a minority arising as part ofNeurofibromatosis type 1 [16]. Ultrasound and CT show a solid mass, andultrasound may show expansion of the parent nerve around the tumour(Figure 11) [17]. The mass tends to be homogenous without internalbreakdown. MRI shows signal characteristics that follow fluid, with patchyirregular enhancement on all modalities.

Fig. 11: Ultrasound shows a solid ovoid nodule related to the parent nerve(arrowheads).References: Hong-Jen Chiou, Yi-Hong Chou et al. High-resolution Ultrasonography inSuperficial Soft Tissue Tumors. J Med Ultrasound 2007; 15(3):152-174

• Traumatic neuroma- Rather than a true neoplasm, a traumatic neuromarepresents a disorganised regrowth of the proximal end of a nerve afterneurotmesis. In the context of a suitable history, typical ultrasoundappearance is of a well-defined minimally vascular lesion, hypoechoic tosurrounding subcutaneous tissue.

• Palisaded encapsulated neuroma- These are slow growing benignintradermal tumours of adulthood, commonly found at musculocutaneous

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junctions. Histologically composed of interlacing axons and Schwann cellswithin a fibrous capsule [18]. No specific imaging features are identified inthe literature, and the diagnosis remains histological.

• Granular cell tumour-A relatively common tumour of middle age, affectingthe head and neck with a particular predilection for the tongue. Generallybenign. There is a 1-2% incidence of malignancy. There are no specificimaging features but oval, hypoechoic lesions have been described onultrasound [19]. Diagnosis remains histological.

Conclusion

Benign skin and subcutaneous lesions presenting as neck lumps can often be reliablycharacterised with imaging thus preventing the need for unnecessary biopsies or surgery.Frequently encountered, incidental subcutaneous lesions may be confidently 'left alone'.

Personal information

References

[1] Ahmed Abdel Razek, Benjamin Y Huang. Soft Tissue Tumours of the Head and Neck:Imaging-based Review of the WHO Classification. Radiographics 2011; 31:1923-1954.

[2] Taiseer Hussain Al-Khateeb et al. Cutaneous cysts of the Head and Neck. J OralMaxillofac Surg 67:52-57, 2009.

[3] Wei-Hsin Yuan et al. Differences in Sonographic Features of Ruptured and UnrupturedEpidermal Cysts. J Ultrasound Med 2012; 31:265-272

[4] Sung Hwan Hong et al. MRI Findings of Subcutaneous Epidermal Cysts: Emphasison the Presence of Rupture. AJR 2006; 186:961-966.

[5]Gossner J, Larsen J. Incidental subcutaneous nodules on the scalp in patientsundergoing CT of the brain; frequency, appearance and differential diagnosis. ClinicalRadiology 65 (2010); 427-429.

[6] Shepherd G Pryor et al. Pediatric dermoid cysts of the head and neck. Otolaryngology- Head and Neck Surgery. June 2005; Volume 132 Number 6; 938-942

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[7] Justyna Sicinska et al. Cylindroma transforming into basal cell carcinoma in a patientwith Brook-Spiegler syndrome. J Dermatol Case Rep 2007 1, pp04-09

[8] Richard Salzman et al. Pediatric parotidomasseteric pilomatrixoma in childrenBiomedPap Med Fac Univ PalackyOlomoucCzech Repub. 2013; 157:XX.

[9] CDM Fletcher, KK Unni, F Mertens. Pathology and genetics of tumours of soft tissueand bone. In: Kleihus P, Sobin LH, eds. World Health Organisation classification oftumours.Lyon,France: IARC, 2002.

[10] Annabella C K Yim et al. Hibernoma: A Case Series with Multimodality Imaging andPathologic Correlation. Bulletin of theNYUHospitalfor Joint Diseases. 2012;70(4):283-7

[11] Sung Tae Kim et al. Nodular Fasciitis in the Head and Neck: CT and MR ImagingFindings. AJNR. 2005. 26:2617-2623

[12] CE Skoulakis et al. Subcutaneous benign fibrous histiocytoma of the cheek. Casereport and review of the literature.Acta Otorhinolaryngol Ital. 2007 April; 27(2): 90-93.

[13] Connor SE, Flis C, Langdon JD. Vascular masses of the head and neck. Clin Radiol2005;60(8): 856-868.

[14] Som P, Curtin H. Head and Neck Imaging, Ch 29 p1558-60

[15] Beaman FD, Kransdorf MJ, Menke DM. Schwannoma: radiologic-pathologiccorrelation. Radiographics. 24 (5): 1477-81.

[16] Pilavaki M, Chourmouzi D, Kiziridou A et-al. Imaging of peripheral nerve sheathtumors with pathologic correlation: pictorial review. Eur J Radiol. 2004;52 (3): 229-39

[17] Hong-Jen Chiou, Yi-Hong Chou et al. High-resolution Ultrasonography in SuperficialSoft Tissue Tumors. J Med Ultrasound 2007; 15(3):152-174

[18] Golod O, Soriano T, Craft N. Palisaded encapsulated neuroma--a classicpresentation of a commonly misdiagnosed neural tumor. J Drugs Dermatol 2005 Jan-Feb;4(1):92-4.

[19] Kei Aoyama, Takako Kamio et al. Granular cell tumors: a report of sixcases. World J Surg Oncol. 2012; 10:204. Published online September 2012 doi:10.1186/1477-7819-10-204

http://www.ncbi.nlm.nih.gov/pubmed/?term=Skoulakis%20C%5Bauth%5D

http://www.ncbi.nlm.nih.gov/pubmed/15696992?dopt=Abstract

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