Determining whether a lump on the skin is cancerous is a common concern for many patients. A dermatologist is a medical doctor who specializes in diseases of the skin, hair, and nails. They have extensive training and experience evaluating skin growths and lumps and determining if they are cancerous or benign.
What training does a dermatologist receive?
After completing medical school, a dermatologist undergoes several additional years of specialized training dedicated to diagnosing and treating more than 3000 diseases of the skin, hair, and nails. This includes:
- 3 years of residency training in dermatology
- Training in histopathology to examine skin samples under a microscope
- Training in surgical techniques to remove skin cancers
With this extensive education, dermatologists become experts at visually inspecting the skin and recognizing when a growth looks suspicious for cancer. They also regularly perform biopsies to remove all or part of a lump and send it to pathology for microscopic examination. This helps them determine if abnormal cells are present that could indicate cancer.
How does a dermatologist evaluate a lump on the skin?
During an appointment, a dermatologist will first visually inspect the lump, looking carefully at its characteristics. Features that may indicate cancer include:
- Asymmetry – the two halves look different
- Irregular borders – the edges are ragged or not well-defined
- Color variation – there are different shades of brown/black/red/white
- Large diameter – generally > 6mm
- Evolution – the lump has changed size, shape, color recently
The dermatologist will palpate (feel) the lump to determine if it is elevated above the skin or fixed to underlying tissues. Cancerous lumps are often firm or hard.
The dermatologist will also ask about the lump’s duration, any associated symptoms like itching/pain, risk factors like sun exposure, and family history of skin cancer. All of this information guides their level of suspicion that the lump could be cancerous.
Tools used to evaluate a lump
In addition to a visual inspection, dermatologists have other tools that facilitate evaluating suspicious lumps:
- Dermatoscope – A special magnifying instrument lets the dermatologist examine the lump’s features with 10x magnification. This helps detect subtle visual characteristics of cancer.
- Skin biopsy – Removing all or part of the lump for microscopic examination is the most accurate way to determine if cancer cells are present. There are several biopsy techniques.
- Punch biopsy – A round blade is rotated down through the skin to remove a small core of tissue.
- Shave biopsy – A small razor blade is used to shave off the raised portion of a lump.
- Excisional biopsy – The entire lump is surgically cut out and removed.
- Imaging tests – For larger or deeper lumps, imaging such as ultrasound, CT, or MRI can help evaluate the lump’s extent and involvement of deeper tissues.
When is a biopsy warranted?
Dermatologists have a low threshold for performing a biopsy on lumps with any concerning features for cancer. Even if the clinical suspicion is low, a biopsy is often warranted if the lesion is changing or fits any of these criteria:
- diameter > 6mm
- continues to grow over 2-3 months
- bleeds easily when scratched or bumped
- is asymmetric or has an irregular border
- Different colors are present
- Is solid or firm to the touch
- Appears suddenly or grows rapidly
Catching a potential skin cancer early leads to the simplest treatments and best outcomes. Dermatologists would rather perform a benign biopsy than delay diagnosing a malignant lump.
How accurate are dermatologists at detecting skin cancer?
Dermatologists have proven expertise at evaluating suspicious lumps based on visual inspection and dermatoscopic evaluation:
- In one study, experienced dermatologists were able to distinguish benign moles from melanoma with 95-100% accuracy based solely on macroscopic visual assessment. (Fried et al. 1998)
- Adding dermatoscopy to macroscopic inspection has been shown to improve diagnostic accuracy by up to 30% compared to visual inspection alone. (Kittler et al. 2002)
Their diagnostic accuracy is enhanced by performing a biopsy on lumps with any concerning features. Biopsy pathology represents the gold standard for confirming if a lump is cancerous or benign.
When to see a dermatologist
The American Academy of Dermatology recommends seeing a dermatologist if you notice any new or changing lumps or spots on your skin, especially if they exhibit any of the ABCDE criteria of melanoma:
- Asymmetry – One half does not match the other half
- Borders – The edges are irregular or blurred
- Color – There are different shades of black, brown, red, white, or blue within the mole
- Diameter – The spot is larger than 6mm, about the size of a pencil eraser
- Evolving – The mole is changing in size, shape, or color
Other warning signs to bring to a dermatologist sooner rather than later include:
- A new spot that is growing rapidly or bleeding
- An existing mole that is changing or looks different from others
- A spot that looks shiny, waxy, smooth, or translucent
- Development of a lump anywhere on the skin that persists longer than a month
Do not wait for a skin lump to hurt before getting it evaluated. Skin cancers rarely cause pain in their early stages.
Can a dermatologist always determine if cancer is present?
In most cases, an experienced dermatologist can determine with a high degree of accuracy whether a concerning lump is likely to be cancerous strictly based on the clinical evaluation during an office visit. However, there is no way for a dermatologist to know with 100% certainty that a lesion is cancerous or benign without performing a biopsy.
There are some rare skin cancers like amelanotic melanoma that do not produce pigment and can masquerade as benign lesions. In these cases, a biopsy is needed to establish the diagnosis. Dermatologists have a very low threshold for performing biopsies on any suspicious lumps to determine their true nature.
Takeaway points
- Dermatologists are skin cancer experts, with specialized training in diagnosing skin cancer.
- Dermatologists evaluate lumps based on appearance, feel, associated symptoms and risk factors.
- Tools like dermatoscopy and biopsy help dermatologists accurately classify lumps.
- See a dermatologist promptly if you notice a new or changing lump on your skin.
- A biopsy is often needed to confirm whether a concerning lump is cancerous or benign.
The bottom line
In most cases, an experienced dermatologist can determine with a high degree of accuracy if a concerning skin lump has a high probability of being cancerous based on the clinical evaluation during an office visit. However, a biopsy is often needed to confirm with 100% certainty if cancer is truly present, especially if the lump has any suspicious features for melanoma or other skin cancer. Do not hesitate to see a dermatologist if you notice a new or changing lump on your skin. Catching potential skin cancers early leads to the simplest treatments and best outcomes.