Differentiating Benign Skin Lesions from Skin Cancer
A new skin lesion that you had never noticed before is always a reason for concern. This concern can in select cases be lifesaving owing to the timely diagnosis and treatment of otherwise fatal malignancies. Everyone needs to be constantly vigilant and aware of any suspicious appearing skin lesions due to the poor prognosis associated with a delayed diagnosis of skin cancer. But what is the description of a suspicious skin lesion? Does every mole, freckle and blemish need a skin biopsy to rule out the possibility of a malignant tumor? No, it doesn’t. More often than not, a freckle is just a freckle and will require no further management.
Therefore, any new skin lesion needs to be examined by a professional before jumping to conclusions with a self-assumed diagnosis. To this end the question again arises, what types of skin lesion need a professional opinion? In order to understand this, you will need to know the typical warning signs of a premalignant or malignant skin lesions, which will be discussed below.
Typical Morphological Characteristics of a Malignant Skin Lesion
Size: A new or previously existing skin lesion that changes in size either gradually or rapidly over a period of weeks to even years can be a sign of malignancy. If a new skin lesion is greater than 5mm in diameter, it is best to have it examined.
Appearance: The lesion appears irregular and doesn’t conform to typical feature of moles or freckles. Abnormal non-uniform color, structure and surface of the skin lesion are typical features of a malignant lesion. Multiple skin lesions of new onset with abnormal morphology is an important warning sign that needs to promptly be examined.
Keratin Plug: Keratin plugs can be a benign finding but presence of a large keratin plug over nodules greater than 5 mm in diameter with a suspicious appearance demands a visit to a dermatologist.
Ulcerations or Crust: Skin lesions with spontaneous development of crusts or ulcerations without history of any trauma or irritation is another red flag that needs urgent evaluation.
Adherent Scale: Scales are not a finding of a normal healthy skin, and can be caused by a number of genetic, allergic or autoimmune etiologies. Sometimes, it can also be a sign of a premalignant skin lesion such as actinic keratosis, Bowen disease, lichen planus, etc.
Erythematous Halo: A ring or halo of redness around a nodule or papule resembling a bulls eye pattern can also be seen in malignant skin lesions and therefore needs to be further examined.
Location of the lesion: Although skin cancer can appear in any part of the body, some areas are more prone to develop malignant lesions such as the scalp, peri-ocular region, genital orifices, ungual area, and orifices. Lesions in these regions always require a specialist’s eye for evaluation.
Growth Pattern: Rapidly growing aggressive growth pattern warrants urgent evaluation.
Distinguishing Features Of Skin Cancer Subtypes
Skin Cancer is a broader term for various cancerous skin lesions including many subtypes. Each of them exhibit their own unique distinguishing features such as:
Melanoma
Melanoma is a cancer of the melanocytes present in the basal layer of the epidermis. Its features can be remembered with the easy mnemonic ABCDE
A– Asymmetry
B– Border Irregularity
C– Color Variation
D– Diameter greater than 6mm
E– Evolving
Often, early lesions of melanoma are ignored by the patient due to their similarity in appearance with freckles and moles. All are pigmented and appear benign and can only be differentiated via a biopsy in the early stages. Any mole that display the ABCDE characteristics needs to be evaluated. It should be noted that previously benign mole or freckle may undergo malignant transformation as well.
Squamous cell carcinoma
Squamous cell carcinoma is a cancer of the epidermis which is made of stratified squamous epithelium. They often develop in the form of a plaque or a nodule over a period of weeks to months and can become ulcerated. Painful ulcerated nodules should raise the suspicion of squamous cell carcinoma.
Basal Cell Carcinoma
Basal cell carcinoma involves the basal layer of the epidermis, and usually presents with a typical nodulo-ulcerated lesion with early bleeding. Its growth is slower than squamous cell carcinoma and it can take years for the patient to seek an expert’s opinion due to their relatively slower growth pattern. Therefore, any persisting skin lesion that doesn’t go away within a few weeks should be examined regardless of the growth rate.
Morphological Features of a Benign Skin Lesion
To further aid you in differentiating benign from malignant skin lesions, it is imperative to also know the features of a benign skin lesion.
Size: The size remains constant, stable and grows either very slowly or not at all over decades.
Appearance: Uniform color, shape and structure with no ulcerations, plaques, bleeding or Erythematous ring.
Stability: The size, shape, color and structure of a benign skin lesion doesn’t change over time.
The typical features described above are as stated: typical i.e. they are commonly seen features of malignancy, but atypical cases may not present in a similar manner. Furthermore, all the above features are not a criterion for diagnosis as some malignant skin lesions may present with only one of the above features or in atypical cases none of the above features.
In high risk people such as people with frequent sun exposure, elderly people, smokers, or with genetic predisposition to malignancy, all skin lesions should be considered to have malignant potential until examined thoroughly by an experienced dermatologist familiar with skin cancer.
References
Cancer 2014 Sep 03;[EPub Ahead of Print], VR Belum, AC Rosen, N Jaimes, G Dranitsaris, MP Pulitzer, KJ Busam, AA Marghoob, RD Carvajal, PB Chapman, ME Lacouture
Ribas A, Flaherty KT. BRAF targeted therapy changes the treatment paradigm in melanoma. Nat Rev Clin Oncol. 2011; 8: 426‐ 433.
Jaimes N, Zalaudek I, Braun RP, Tan BH, Busam KJ, Marghoob AA. Pearls of keratinizing tumors. Arch Dermatol. 2012; 148: 976.
Rosendahl C, Cameron A, Argenziano G, Zalaudek I, Tschandl P, Kittler H. Dermoscopy of squamous cell carcinoma and keratoacanthoma. Arch Dermatol. 2012; 148: 1386‐ 1392.
Lacouture M, Chapman PB, Ribas A, et al. Presence of frequent underlying RAS mutations in cutaneous squamous cell carcinomas and keratoacanthomas (cuSCC/KA) that develop in patients during vemurafenib therapy [abstract]. J Clin Oncol. 2011; 29(suppl): 8520.