Superficial spreading melanoma
Encyclopedia
Superficial spreading melanoma (also known as "Superficially spreading melanoma") (SSM) is usually characterized as the most common form of cutaneous melanoma
in Caucasians. The average age at diagnosis is in the fifth decade, and it tends to occur on sun-exposed skin, especially on the backs of males and lower limbs of females.
. Otherwise it arises in previously normal skin. A prolonged radial growth phase, where the lesion remains thin, may eventually be followed by a vertical growth phase where the lesion becomes thick and nodular. As the risk of spread varies with the thickness, early SSM is more frequently cured than late nodular melanoma.
The microscopic hallmarks are:
and possibly sentinel node biopsy
. Spread of disease to local lymph nodes or distant sites (typically brain, bone, skin and lung) marks a decidedly poor prognosis.
Melanoma
Melanoma is a malignant tumor of melanocytes. Melanocytes are cells that produce the dark pigment, melanin, which is responsible for the color of skin. They predominantly occur in skin, but are also found in other parts of the body, including the bowel and the eye...
in Caucasians. The average age at diagnosis is in the fifth decade, and it tends to occur on sun-exposed skin, especially on the backs of males and lower limbs of females.
Presentation
Often, this disease evolves from a precursor lesion, usually a dysplastic nevusDysplastic nevus
A dysplastic nevus is an atypical melanocytic nevus; a mole whose appearance is different from that of common moles. Dysplastic nevi are generally larger than ordinary moles and have irregular and indistinct borders...
. Otherwise it arises in previously normal skin. A prolonged radial growth phase, where the lesion remains thin, may eventually be followed by a vertical growth phase where the lesion becomes thick and nodular. As the risk of spread varies with the thickness, early SSM is more frequently cured than late nodular melanoma.
The microscopic hallmarks are:
- Large melanocytic cells with nest formation along the dermo-epidermal junction.
- Invasion of the upper epidermis in a pagetoidPagetoidPagetoid is a term used in dermatology to refer to "upward spreading" of melanocytes into the epidermis. It is uncommon and a possible indication of a precancerous or cancerous condition. Cells display pagetoid growth when they invade the upper epidermis from below. Squamous cell carcinoma,...
fashion (discohesive single cell growth). - The pattern of rete ridges is often effaced.
- Invasion of the dermis by atypical, pleomorphic melanocytes
- Absence of the 'maturation' typical of naevus cells
- Mitoses
Treatment
Treatment is by excisional biopsy, wide local excisionWide local excision
A wide local excision is a surgical procedure to remove a small area of diseased or problematic tissue with a margin of normal tissue. This procedure is commonly performed on the breast and to skin lesions, but can be used on any area of the body....
and possibly sentinel node biopsy
Sentinel lymph node
The sentinel lymph node is the hypothetical first lymph node or group of nodes reached by metastasizing cancer cells from a primary tumor.-Physiology:...
. Spread of disease to local lymph nodes or distant sites (typically brain, bone, skin and lung) marks a decidedly poor prognosis.