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These cutaneous cysts are generated by the implantation of epidermal components in the dermis and subcutaneous tissue. Thus, the causes can be embryonic, traumatic or secondary to surgical procedures. Epidermal cysts are covered by stratified squamous epithelium with a granular layer. Hence, the name "sebaceous cyst" is a misnomer and may be confusing.
Clinically, they usually show as erythematous and sometimes painful nodules, often with a small opening on the surface, also called “punctum” which correspond to the communication of the cyst with the epidermal layer. These cysts may drain foul smelling and cheesy-like material and contain keratin, cholesterol and sometimes calcifications.
One of the problems with epidermal cysts is that they can be potent simulators of other lesions, especially when the wall of the cyst ruptures and the cyst become inflamed. Therefore, they can mimic pilomatrixomas, dermatofibromas, foreign bodies, among other lesions. Furthermore, to prevent recurrence, the wall of the cyst (that generates the keratin) should be completely removed.
On sonography, they show a variable appearance according to the phase of the cyst. If they are intact, the sonograms will usually show a well defined, rounded- or oval shaped, anechoic or hypoechoic structure located in the dermis and subcutaneous tissue. Also, these cysts may present inner echoes (debris) and sometimes show a “pseudotestes appearance” ( ie. brighter inner echoes and anechoic filiform areas) as the result of highly compacted deposits of keratin and cholesterol. Commonly, a connecting anechoic tract (punctum) to the epidermis can be detected on ultrasound.
Nevertheless, when the cyst is complicated with a rupture, the keratin is spread into the surrounding tissue and elicits inflammation and a foreign body reaction. The latter events may cause hypoechoic collections, adjacent to the cysts or a big change in the morphology of the cysts that turn into ill-defined hypoechoic structures.
Interestingly, posterior acoustic enhancement, a classical artifact of the cystic lesions, is usually conserved during all the phases. Ultrasound can show the lesion and measure the extent in all axes as well as demonstrate the connecting tracts and perform the differential diagnosis with other conditions. Moreover, color Doppler ultrasound may show increased blood flow in the periphery of the cysts during the phases of inflammation and rupture, frequently with low- flow vessels.
The proper recognition and assessment of the extent of these cystic entities through the sum of the clinical and anatomical data provided by sonography may support an early diagnosis and proper treatment. Thus, the addition of the ultrasound technology perhaps may help to deal with these entities, turning a possible nightmare into a dream.
Figure 2. Intact epidermal cyst. Ultrasound (transverse view) shows rounded shaped , anechoic structure (c, cyst) in the dermis (d) and subcutaneous tissue (st).
Figure 3 (A, B) . Pseudotestes appearance in intact epidermal cysts. Ultrasound images (transverse views) demonstrate filiform anechoic bands (arrowheads) and hyperechoic lines (arrows) within the cysts. Notice the posterior acoustic enhancement (pae) at the bottom of the cysts. Abbreviations: d, dermis; st, subcutaneous tissue.
Figure 4. Epidermal cyst 3D ultrasound reconstruction. Notice the connecting tract (punctum) of the cyst to the surface.
Figure 5. Ruptured epidermal cyst. A. Ultrasound ( grey scale, transverse view) shows ill defined hypoechoic structure (c, cyst) with hypoechoic bands (arrows) that correspond to the keratin deposits spread into the surrounding tissue. B. Color Doppler ultrasound (transverse view) demonstrates the increased blood flow in the periphery of the cyst. Abbreviations: d, dermis; st, subcutaneous tissue; c, cyst; pae, posterior acoustic enhancement.
1-Huang CC, Ko SF, Huang HY, Ng SH, Lee TY, Lee YW, Chen MC.Epidermal cysts in the superficial soft tissue: sonographic features with an emphasis on the pseudotestis pattern.J Ultrasound Med. 2011;30:11-7.
2-Jin W, Ryu KN, Kim GY, Kim HC, Lee JH, Park JS. Sonographic findings of ruptured epidermal inclusion cysts in superficial soft tissue: emphasis on shapes, pericystic changes, and pericystic vascularity. J Ultrasound Med. 2008;27:171-6
3-Kuwano Y, Ishizaki K, Watanabe R, Nanko H. Efficacy of diagnostic ultrasonography of lipomas, epidermal cysts, and ganglions. Arch Dermatol. 2009 ;145:761-4.
4-Wortsman X, Wortsman J, Clinical usefulness of variable frequency ultrasound in localized lesions of the skin. J Am Acad Dermatol 2010; 62 : 247-256
5-Wortsman X.Common applications of dermatologic sonography.J Ultrasound Med. 2012 ;31:97-111
Pilomatrixomas, also called pilomatricomas or calcifying epitheliomas of Malherbe are common and benign skin tumors that arise from the hair follicle matrix. These conditions are more common in children and young adults, especially on the head, neck and extremities. Clinically, they usually present as single or multiple painless, erythematous or slightly bluish nodules. Thus, these tumors can easily mimic other cutaneous lesions such as epidermal cysts, foreign body reactions, fat necrosis, calcified lymph nodes or vascular tumors, among others, on the clinical examination. Moreover, clinical misdiagnosis has been reported as high as 54% in some series.
On sonography, pilomatrixomas classically appear as target-shaped nodules with well-defined hypoechoic rim and hyperechoic center. Scattered hyperechoic dots producing posterior acoustic shadowing that correspond to calcium deposits may be found within the nodule nucleus (partial calcification). Nevertheless, 15 to 30% of pilomatrixoma cases had been reported to not show calcium and 45 % of these entities, in other series, had been reported as completely calcified. Furthermore, there are rare cystic variants of pilomatrixomas. On the other hand, variable degrees of vascularity can be present within the tumor which may also explain the challenging clinical diagnosis.
Ultrasound had reported correctness of diagnosis from 76% to 96% and provides reliable information about the extension, location and blood flow of the lesions. Therefore, a pre-surgical sonographic examination may be a good tool for removing the clinical disguise of these tumors.
Figure 1 (A-D). Sonographic Patterns of Pilomatrixomas. A. Round shaped structure with hypoechoic rim and hyperechoic center (target-shaped). The hyperechoic dots (*) represent the low and partial presence of calcifications within the nodule. B. Another case presenting a higher degree of calcification but similar echostructure.C. Completely calcified pilomatrixoma shows a hyperechoic band (*) in the junction of the dermis and subcutaneous tissue that presents posterior acoustic shadowing artifact (as). D. Cystic variant of pilomatrixoma demonstrates a solid-cystic structure with a hypoechoic nodular part (*) associated to an anechoic fluid-filled cystic component (f) surrounded by a hypoechoic rim (r) and some septa (arrowhead).Abbreviations: d, dermis, st, subcutaneous tissue.
Figure 2 (A-C). Sonographic Vascularity Patterns of Pilomatrixomas going from low (A) to high (C) blood flow on color Doppler ultrasound.
1-Roche NA, Monstrey SJ, Matton GE. Pilomatricoma in children: common but often misdiagnosed. Acta Chir Belg. 2010 ;110:250-254.
2-Kumaran N, Azmy A, Carachi R, Raine PA, Macfarlane JH, Howatson AG. Pilomatrixoma--accuracy of clinical diagnosis. J Pediatr Surg. 2006 ;41:1755-1758.
3-Choo HJ, Lee SJ, Lee YH, Lee JH, Oh M, Kim MH, Lee EJ, Song JW, Kim SJ, Kim DW. Pilomatricomas: the diagnostic value of ultrasound. Skeletal Radiol. 2010;39:243-250.
4- Solivetti FM, Elia F, Drusco A, Panetta C, Amantea A, Di Carlo A. Epithelioma of Malherbe: new ultrasound patterns. J Exp Clin Cancer Res. 2010 6;29:42.
5-Wortsman X, Wortsman J, Arellano J, Oroz J, Giugliano C, Benavides MI, Bordon C. Pilomatrixomas presenting as vascular tumors on color Doppler ultrasound. J Pediatr Surg. 2010;45:2094-2098.
6-Wortsman X.Common applications of dermatologic sonography.J Ultrasound Med. 2012 ;31:97-111
Pilonidal cysts are common lesions that arise in the intergluteal region. These cysts are more frequent in young men and usually contain hair fragments and debris. Clinically, pilonidal cysts present as acute or chronic abscesses, with intermittent discharge or bleeding. Treatment is surgical; however, recurrences are common representing an important problem for managing. Also, these entities are associated to high morbidity and slow wound healing. Therefore, pilonidal cysts may easily impact upon body image and self-esteem.
Few imaging studies had been focused on pilonidal cysts, although, recently with the development of newer generations of variable frequency ultrasound machines, these lesions have been among the common targets for studying.
On ultrasound, these cysts show as hypoechoic debris-filled collections in the dermis and subcutaneous tissue. Commonly, they contain hyperechoic lines that correspond to hair fragments within the cysts. Thus, when pilonidal cysts become inflamed and/or infected, color Doppler ultrasound demonstrates increased blood flow in the periphery and/or within the cyst.
Recurrences may occur by several reasons, however they could be easily related with the intrinsic anatomy of the cyst; for e.g. often, pilonidal cysts are much more extensive than clinically suspected, and may end many cm, (for e.g., 6 or 7 cm) downward from the location level of the main skin opening (cutaneous lesion level). Moreover, usually the longest diameter and main direction of the cyst runs longitudinally, however, transverse or oblique directions as well as branches of the same cyst going in opposite directions such as upward/ downward or left /right from the main skin opening are not uncommon presentations.
Thus, pre-surgical knowledge of detailed anatomical data such as extension, location and main axis of pilonidal cysts may improve intra-operative planning and decrease recurrences. Additionally, non invasive sonographic imaging allows a better understanding of the pathogenesis of this entity in real time therefore if needed, may provide the capability of intra-operative sonographic guidance.
Figure 2. Extensive Pilonidal Cyst . Ultrasound ( longitudinal panoramic field of view) in the intergluteal region shows a 6.38 cm pilonidal cyst (between markers). Notice the white arrow pointing the location level of the skin opening far from the bottom of the cyst located in right side of the image.
Figure 3 (A-B). Pilonidal cyst following a transverse direction. A. Ultrasound (transverse view) in the left intergluteal region demonstrates a pilonidal cyst following a transverse direction. B. Color Doppler ultrasound of the same case shows increased blood flow within the lesional area. Abbreviations: d, dermis; st, subcutaneous tissue.
Figure 4. Pilonidal Cyst presenting upward and downward branches. Ultrasound (longitudinal panoramic view) shows a pilonidal cyst with 2 branches going in opposite direction. The red line is marking the location of the upward branch (2.3 cm long) and the white line is marking the location of the downward branch (4.6 cm long). A white vertical line is showing the junction between both branches and a white arrow is pointing the location level of the skin opening.
Figure 5. Pilonidal Cyst with Multiple Hair Fragments and Communicating to the Base of Multiple Hair Follicles. Ultrasound (longitudinal view) demonstrates multiple white hyperechoic lines (*) that correspond to hair fragments within the cyst. Also, multiple hypoechoic tracts show the communication of the cyst with the base of enlarged hair follicles.
Lastly, you can check the video gallery and look for a live ultrasound imaging of a pilonidal cyst.
1- Al-Khamis A, McCallum I, King PM, Bruce J.Healing by primary versus secondary intention after surgical treatment for pilonidal sinus.Cochrane Database Syst Rev. 2010 Jan 20
2- Humphries AE, Duncan JE.Evaluation and management of pilonidal disease.Surg Clin North Am. 2010 ;90:113-124
3- Wortsman X, Wortsman J.Clinical usefulness of variable-frequency ultrasound in localized lesions of the skin.J Am Acad Dermatol. 2010 ;62:247-256.
4- Mentes O, Oysul A, Harlak A, Zeybek N, Kozak O, Tufan T.Ultrasonography accurately evaluates the dimension and shape of the pilonidal sinus.Clinics (Sao Paulo). 2009;64:189-192
5-Wortsman X.Common applications of dermatologic sonography.J Ultrasound Med. 2012 ;31:97-111
LIPOMAS WITH DANGEROUS LIAISONS DETECTED BY ULTRASOUND
Lipomas are benign tumors derived from the fatty tissue and are the most frequent soft tissue tumors. They can present as single or multiple masses and their superficial (subcutaneous) location is much more frequent than the deep one. Commonly, the adipose tissue can be associated to other tissues such as mesenchymal fibrous connective tissue (fibrolipoma) or capillary components (angiolipoma).
On sonography, lipomas usually appear as oval-shaped and well circumscribed solid tumors that follow the same axis of the skin layers. Their echogenicity can vary from hypoechoic to hyperechoic according to the amount and type of the non-fatty tissue attached to the mature adipocytes. Therefore, they can show an hypoechoic appearance when containing more fibrous components and an hyperechogenicity when capillaries are prominent within the tumor. Also, the internal architecture usually presents multiple hyperechoic lines and none or scarce blood flow within masses.
Sometimes, these tumors can present more risky locations such as the anterior neck, elbow or groin where thick vessels can be close to the lesions and may potentially complicate surgery. Also, lipomas may be close to nerves and elicit pain by extrinsic compression. The anatomical information provided by ultrasound can allow an adequate planning of the surgical procedures making known extension and the relevant anatomical relations of these common soft tissue entities.
Figure 2A. Ultrasound ( transverse axis) in the right side of the anterior neck shows an hypoechoic subcutaneous lipoma superficial to the external jugular vein. Abbreviations: L, lipoma; EYV, external jugular vein; ECM, sternocleidomastoideous muscle; D, dermis; ST, subcutaneous tissue.
Figure 2B. Color Doppler ultrasound (transverse axis) demonstrates the blood flow within the external jugular vein (distance between the lipoma and the external jugular vein: 1.5 mm).Abbreviations: L,lipoma; EYV, external jugular vein; ECM, sternocleidomastoideous muscle.
Figure 3. Ultrasound (transverse view) at the posterior forearm shows a subcutaneous lipoma located in the vicinity of the ulnar nerve ( 8.4 mm distance). Abbreviations: L, lipoma; UN, ulnar nerve.
Figure 4. Color Doppler ultrasound (longitudinal axis) at the anterior elbow shows a subcutaneous lipoma superficial to the brachial artery. Abbreviations: L, lipoma; BA, brachial artery.
1-Kuwano Y, Ishizaki K, Watanabe R, Nanko H.Efficacy od diagnostic ultrasonography of lipomas, epidermal cysts, and ganglions.. Arch Dermatol. 2009;145:761-764.
2-Hsu YC, Shih YY, Gao HW, Huang GS.Subcutaneous lipoma compression the common peroneal nerve and causing palsy: sonographic diagnosis. J Clin Ultrasound. 2010 ;38:97-99.
3-Yang DM, Kim HC, Lim JW, Jin W, Ryu CW, Kim GY, Cho H. 120. Sonographic findings of groin masses. . J Ultrasound Med. 2007 ;26:605-614.
4-Wortsman X, Wortsman J, Clinical usefulness of variable frequency ultrasound in localized lesions of the skin. J Am Acad Dermatol 2010; 62: 247-256