Conflict of interest: none.
Dermoscopy of uncommon skin tumours
Article first published online: 19 JUL 2013
© 2013 The Authors. Australasian Journal of Dermatology © 2013 The Australasian College of Dermatologists
Australasian Journal of Dermatology
Volume 55, Issue 1, pages 53–62, February 2014
How to Cite
Lallas, A., Moscarella, E., Argenziano, G., Longo, C., Apalla, Z., Ferrara, G., Piana, S., Rosato, S. and Zalaudek, I. (2014), Dermoscopy of uncommon skin tumours. Australasian Journal of Dermatology, 55: 53–62. doi: 10.1111/ajd.12074
Aimilios Lallas, MD. Elvira Moscarella, MD. Giuseppe Argenziano, MD. Caterina Longo, MD. Zoe Apalla, MD. Gerardo Ferrara, MD. Simonetta Piana, MD. Simonetta Rosato, MD. Iris Zalaudek, MD.
- Issue published online: 17 JAN 2014
- Article first published online: 19 JUL 2013
- Manuscript Accepted: 1 APR 2013
- Manuscript Received: 18 MAR 2013
- Italian Ministry of Health. Grant Number: RF-2010-2316524
angiosarcoma of the head and scalp
basal cell carcinoma
lymphoedema associated angiosarcoma
Merkel cell carcinoma
malignant fibrous histiocytoma
radiation induced angiosarcoma
squamous cell carcinoma
There is mounting evidence that dermoscopy significantly improves the clinical diagnosis of most skin tumours and in consequence, dermoscopy is nowadays an integral part of the clinical skin examination.[1-3] The dermoscopic patterns of most common skin tumours, including melanocytic naevi, seborrhoeic keratoses, dermatofibromas, vascular tumours, melanomas, basal cell carcinomas (BCC) and squamous cell carcinomas (SCC) are well defined and established in everyday practice.[4-6] However, a range of uncommon skin tumours exists and their dermoscopic patterns have been described only sporadically. Here we provide a review of the literature on the dermoscopic patterns of uncommon skin tumours along with representative examples from our database.
In this retrospective study we searched our database for clinical and dermoscopic images of histopathologically diagnosed rare skin tumours using the following keywords: Merkel cell carcinoma (MCC), mesenchymal tumour, adnexal tumour and fibrous tissue tumour. Tumours diagnosed as any type of melanocytic naevus, melanoma, seborrhoeic keratosis, haemangioma, angiokeratoma, pyogenic granuloma, dermatofibroma, BCC and SCC were excluded. All dermoscopic images were evaluated by two dermatologists (AL and EM) in consensus for the presence of specific morphological patterns. The dermoscopic criteria included: (i) vascular pattern (morphology and distribution of vessels), (ii) background colour, (iii) pigmentation structures and (iv) additional structures. If a disagreement arose between both evaluators the criterion was judged as being absent. A review of the literature was performed on PubMed Central with the keywords ‘dermoscopy’, ‘dermatoscopy’ and the name of each tumour.
A total of 85 rare skin tumours with 26 different histopathological diagnoses meeting the search criteria were extracted from our database (Table 1). The outcome of the literature search included 48 studies describing dermoscopic criteria of 20 different entities (Table 1). Combining the results of our analysis and previously published data, in Tables 2 and 3 we summarise the dermoscopic criteria of 26 uncommon skin tumours.
|Tumour||No of cases in our series||No of cases published|
|Merkel cell carcinoma[7-10]||6||23|
|Angiosarcoma of the head and scalp||3||9|
|Primary cutaneous carcinosarcoma||1||1|
|Langerhans cell sarcoma||1||0|
|Malignant fibrous histiocytoma||1||0|
|Sebaceous adenoma[19, 22]||3||19|
|Merkel cell carcinoma||Milky red background|
|Polymorphous vascular pattern (dotted, glomerular, arborising, linear irregular)|
|AS||Combinations of red, purple and blue colour|
|RIA||Homogenous pinkish-white pattern|
|Primary cutaneous carcinosarcoma||Polymorphous vascular pattern (dotted, linear vessels, red globules)|
|White (scar-like) lines|
|Langerhans cell sarcoma||Reddish background|
|Polymorphous vascular pattern (dotted, linear vessels, red globules)|
|White (scar-like) lines|
|Atypical fibroxanthoma||Reddish and whitish areas|
|Polymorphous vascular pattern (dotted, linear irregular, hairpin, tortuous)|
|Malignant fibrous histiocytoma||Polymorphous vascular pattern (dotted, linear irregular)|
|Dermatofibrosarcoma protuberans||Reddish background colour|
|Fine linear vessels regularly distributed|
|Sebaceous cyst||White/yellow central structure|
|Peripheral telangiectasias (crown vessels)|
|Sebaceous hyperplasia||White polylobular central structures|
|White structureless centre|
|Central umbilication (bonbon toffee sign)|
|Peripheral telangiectasias (crown vessels)|
|Sebaceous adenoma||Central opaque whitish structure|
|Peripheral telangiectasias (crown vessels)|
|Sebaceoma||Homogenous yellowish central structure|
|Peripheral telangiectasias (crown vessels)|
|Sebaceous carcinoma||Polymorphous vascular pattern|
|Homogenous yellowish background|
|Trichodiscoma||Whitish globular structures|
|Blurred linear vessels|
|Perivascular whitish halos|
|Trichilemmal cyst||White-yellowish central structure|
|Peripheral linear branched vessels|
|Diffuse homogenous blue pigmentation|
|Trichoblastoma||Arborising vessels and blue-grey dots or globules|
|Desmoplastic||Ivory-white background colour|
|Pilomatricoma||Irregular white and/or yellow structures white streaks|
|Reddish homogenous areas|
|Trichilemmal carcinoma||Polymorphous vascular pattern|
|Cylindroma||Unfocused arborising vessels|
|Hidradenoma||Homogenous blue pattern|
|Amorphous whitish areas|
|Spiradenoma||Faint greyish-bluish hue|
|Hidrocystoma||Structureless skin-coloured/yellowish to bluish areas|
|Syringomas (eruptive)||Yellowish-brownish structureless background|
|Scarce fine linear vessels|
|Syringocystadenoma papilliferum||Polymorphous vascular pattern (linear irregular, glomerular vessels)|
|Perivascular whitish halo|
|Eccrine poroma||Polymorphous vascular pattern perivascular whitish halo|
|Porocarcinoma||Polymorphous vascular pattern (dotted, linear irregular vessels)|
|Mucinous carcinoma||Whitish network|
Rare skin tumours may escape clinical diagnosis, since they are not at the frontline of a clinician's differential diagnosis spectrum. Moreover, their clinical presentation is often unspecific, impeding their discrimination from other common entities. Dermoscopy may aid the clinical diagnosis of rare skin tumours by displaying unusual criteria that do not match the well-defined patterns of most common skin tumours.
Merkel cell carcinoma
The incidence of MCC has tripled in recent years and is today estimated about 0.24 per 100 000 person-years.[49-51] MCC shows a predilection for elderly white men and immunosuppressed patients.
MCC is a very aggressive carcinoma, associated with a high risk of locoregional and distant spread and poor survival and, effectively, its early detection and wide local excision are mandatory. Clinically, MCC most commonly develops as a persistent, asymptomatic, red or pink nodule that rapidly increases in size over a period of weeks to months (Fig. 1). The most common sites of presentation are the head and neck region and extremities, followed by the trunk and oral and genital mucosa. Because of its unspecific clinical presentation, the differential diagnostic spectrum of MCC is broad, including common malignant tumours (BCC, SCC, melanomas) and benign lesions such as dermatofibroma or haemangioma.[7-10] Diagnosis is often delayed, since more than half of MCC are thought to be benign at the time of biopsy.
Dermoscopy of MCC typically reveals a milky red background and a polymorphous vascular pattern, comprising dotted, arborising, linear irregular and glomerular vessels (Fig. 1). Less often, milky red areas are combined with only one morphological type of vessels, usually linear irregular. This dermoscopic pattern cannot be considered specific, since similar findings characterise amelanotic melanoma and other malignant tumours. However, dermoscopy may enhance the discrimination between MCC and benign tumours by revealing features predictive of malignancy. Specifically, milky red areas, which represent the commonest criterion of MCC, are very rarely present in benign lesions (with the exception of pyogenic granulomas), whereas they are frequently detected in amelanotic melanomas. Additionally, the synchronous presence of more than one morphological type of vessel (forming the so-called polymorphous vascular pattern) is also suggestive of a malignant tumour, such as melanoma or SCC. Effectively, detection of one or both of the above phenomena should warrant complete surgical excision. The latter is particularly relevant in clinical practice, helping clinicians to avoid diagnostic delay with undesirable consequences for the patient.[7, 9]
Cutaneous angiosarcoma is an aggressive neoplasm that is generally divided into three clinical variants: angiosarcoma of the head and scalp (AS), mainly affecting elderly men; lymphoedema-associated angiosarcoma (LAS) arising typically in the context of Stewart–Treves syndrome and radiation-induced angiosarcoma (RIA) arising in previously irradiated skin areas. Recently, epithelioid angiosarcoma has been described, as a rare, aggressive variant. The classic AS is characterised by a tendency to metastasize to regional lymph nodes and lungs, often after repeated surgical excisions of the primary growth. Prognosis is poor, with a 5-year survival rate of 12–33%. Surgical resection represents the treatment of choice, but its application may be limited by the wide extension of the tumour. Alternatively, AS might respond to a combined treatment consisting of chemotherapy prior to irradiation of the tumour field.
From a clinical point of view, early AS lesions develop as ill-defined violaceous to bluish areas with an indurated border. At this stage, the disease has to be discriminated from bruising, rosacea, tumid lupus erythematosus or infections such as erysipelas and cellulitis. Diagnosis of AS is often suspected at advanced stages when lesions become elevated or nodular and occasionally ulcerated (Fig. 2). Extensive local growth is common, and margins are difficult to define surgically. In approximately half of the patients the disease manifests with multiple separate foci.
RIA and LAS tend to present as reddish to purple plaques with ill-defined borders.
On dermoscopy, the classic AS is characterised by combinations of the typical colours of vascular tumours, namely red, purple and blue (Fig. 2). At the nodular part, white lines corresponding histopathologically to fibrous septa between enlarged neoplastic vascular spaces can be detected. RIA, instead, has been reported to exhibit a more homogeneous pinkish-white pattern.[11, 12, 54]
Tumours of the fibrous tissue
Atypical fibroxanthoma (AFX) and malignant fibrous histiocytoma (MFH) are related tumours with similar histopathological characteristics, but they differ significantly in their prognosis. The former, despite its tendency to recur after incomplete excision, has excellent prognosis, whereas MFH possesses a considerable metastatic potential, being associated with an overall survival rate of 50%.[55-57]
AFX occurs mainly on the sun-exposed parts of elderly individuals. Clinically, it manifests as a rapidly enlarging, reddish, dome-shaped nodule, often with an eroded or crusted surface (Fig. 3a). Less often the tumour acquires a darker hue due to haemosiderin deposition. The clinical differential diagnosis includes melanoma, BCC, SCC and dermatofibrosarcoma protuberans (DFSP). Dermoscopically, AFX displays reddish and whitish areas in combination with a polymorphous vascular pattern consisting of various combinations of linear, dotted, hairpin and highly tortuous vessel irregularly distributed over the surface of the lesion. Ulceration, crusting and keratin masses may also be detected (Fig. 3b).
MFH develops as an enlarging subcutaneous nodule that may acquire significant size and ulcerate (Fig. 3c). As shown in Fig. 3d, dermoscopy reveals a polymorphous vascular pattern comprising dotted, short, fine linear and thick irregular linear vessels, in combination with ulceration and haemorrhage. Like MCC, although findings of AFX and MFH cannot be regarded as specific, dermoscopy minimises the risk of evaluating the tumour as benign. Specifically, detection of a polymorphous vascular pattern should raise suspicion of a malignant tumour, warranting complete surgical excision.
DFSP is a relatively uncommon soft tissue neoplasm, characterised by a low-to-intermediate malignant potential. Analytically, although DFSP rarely metastasizes it is characterised by a locally aggressive biological behaviour and a high recurrence rate. Clinically, it initially presents as one or multiple firm erythematous nodules or plaques that may suppurate or ulcerate (Fig. 4a,c). At this stage, DFSP has to be differentiated from dermatofibroma. The primary lesions gradually enlarge and become confluent, forming characteristic bulky, protuberant neoplastic masses. Dermoscopy might facilitate the clinical recognition of early lesions by revealing a reddish background colour in conjunction with fine linear vessels (Fig. 4b,d). Although the dermoscopic criteria of dermatofibroma have been extensively investigated, a similar pattern has not been reported up to date. A delicate pigment network has also been described in DFSP but it lacks the characteristic peripheral arrangement observed in dermatofibroma.
Adnexal tumours are classified according to their adnexal differentiation as follicular, sebaceous, eccrine and apocrine.[60, 61] Their natural course is generally favourable, although for several benign adnexal tumours a malignant counterpart has also been described. Adnexal carcinomas are associated with a poor prognosis, which is, at least partially, related to their delayed recognition. Our series of tumours included two sebaceous carcinomas, one trichilemmal carcinoma and one porocarcinoma (Fig. 5). As shown in Table 3, almost all malignant adnexal tumours described in the present and previous studies dermoscopically exhibit at least one feature suggestive of malignancy, most commonly a polymorphous vascular pattern.
Although consistent criteria for the diagnosis and nomenclature of sebaceous tumours are lacking, these tumours are traditionally classified as benign sebaceous hyperplasia, sebaceous adenoma, sebaceoma (sebaceous epithelioma) and sebaceous carcinoma. Apart from sebaceous cysts and sebaceous hyperplasia which are common entities, sebaceous tumours are generally rare and typically occur in the context of Muir–Torre syndrome.[62, 63]
Sebaceous hyperplasia is dermoscopically typified by a whitish umbilicated, polylobular or structureless centre, surrounded by elongated, scarcely branching vessels (crown vessels). A similar pattern consisting of central whitish/yellowish structures and crown vessels characterises sebaceous cysts.
Two main dermoscopic patterns of sebaceous adenoma and sebaceoma have been described. First, tumours with a central crater, dermoscopically characterised by elongated radial telangiectasias (crown vessels) surrounding an opaque, structureless ovoid white-yellow centre, which is at times covered by blood crusts. Second, tumours without a central crater, which reveal dermoscopically branching but unfocused arborising vessels over a white to yellow background and few loosely arranged yellow comedo-like globules. The combination of yellowish structures with unfocused arborising vessels is suggestive of the diagnosis of a sebaceous tumour. Differentiating among sebaceous tumours is troublesome, not only clinically but often also histopathologically. Our own and previous results demonstrate that this similarity is reflected also in the dermoscopic patterns of these entities (Fig. 5a,b). Dermoscopy enables their differentiation from sebaceous hyperplasia, which is a common entity, in contrast to the remaining sebaceous tumours, which appear almost exclusively in the context of Muir–Torre syndrome.
Tumours of the hair follicle
In general, the dermoscopic pattern of follicular tumours displays features overlapping with BCC, namely linear branching vessels and blue-grey dots or globules. The common presence of ‘white structures’ has been suggested as a dermoscopic clue, suggestive of the diagnosis of a follicular tumour (Fig. 6). Specific dermoscopic criteria have are associated with some tumours, such as the unique ivory-white background colour that typifies desmoplastic trichoepithelioma (Table 3). A whitish colour can be also detected in morpheaform BCC, but it has a rather scar-like, instead of ivory, hue. Furthermore, morpheaform BCC clinically presents as a flat or depressed firm lesion, unlike trichoblastoma and nodular BCC.
Pilomatricoma or calcifying epithelioma of Malherbe represents the commonest follicular tumour, usually affecting children and adolescents. Irregular white and/or yellow structures, white streaks, reddish homogenous areas and linear vessels represent the most frequent dermoscopic criteria of pilomatricoma, while ulceration and blue-grey areas are common additional findings.[29, 30] The white structures, histopathologically corresponding to calcification or keratin masses, represent the most useful single criterion for differentiating between pilomatricoma and malignant tumours, such as melanoma and BCC.
Sweat gland tumours
Eccrine poroma is the most extensively studied sweat gland tumour, concerning its dermoscopic pattern. It is characterised by a high degree of dermoscopic variability, which is possibly explained by the existence of distinct histopathological subtypes, depending on the location of the basaloid aggregations in relation to the epidermis. Analytically, eccrine poroma may display dermoscopically overlapping features with BCC, such as arborising vessels and blue-grey nests, but more often it exhibits a polymorphous vascular pattern or perivascular whitish haloes, mimicking amelanotic melanoma or keratinising tumours, respectively (Fig. 7).[39-45]
Mucinous carcinoma is characterised by eccrine sweat gland differentiation and represents a low-grade malignant tumour with the potential of local recurrence. Dermoscopy of mucinous carcinoma has been reported to mirror its peculiar histopathology, revealing a whitish network and light-brown globules, which histopathologically correspond to fibrous septum and mucinous deposition, respectively.
A limitation of our study, as well as of all previous studies reviewed here, is related to their design. Specifically, they were descriptive morphological studies without a control group and the accuracy of the proposed dermoscopic criteria cannot be assessed. Another limitation is the variability in definition of dermoscopic features among different studies. Although we attempted to use uniform terminology for the cases described in the current study, we cannot rule out the possibility that in previous studies different terms have been used to describe the same dermoscopic feature, or that some investigators ignored criteria that others included and vice versa.
In conclusion, our results, along with pre-existing evidence, show that dermoscopy, by providing additional morphological information, might enhance the clinical diagnosis of uncommon skin tumours. Although benign adnexal tumours are dermoscopic mimickers of BCC, specific clues such as the whitish structures of follicular tumours and the yellowish structures associated with the crown vessels of sebaceous tumours might aid their recognition. A dermoscopic examination is particularly useful in the context of clinically unspecific and biologically aggressive entities, such as MCC, MFH and adnexal carcinomas, which can often escape clinical detection, with severe consequences. The latter aggressive entities dermoscopically exhibit criteria such as milky red areas or a polymorphous vascular pattern which, although not pathognomonic for a specific diagnosis, are highly suggestive of a malignant tumour. Accordingly, the detection of one (or more) such feature should warrant surgical excision and histopathological confirmation of the diagnosis. Validation of the value of dermoscopy in the diagnosis of uncommon skin tumours requires appropriately designed studies for diagnostic accuracy.
Study supported in part by the Italian Ministry of Health (RF-2010-2316524).
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