Other types of skin cancer
We have discussed the most common of forms of skin cancer, BCC, SCC and melanoma, as well as some of the more common mimics of skin cancer. There are however a few more malignant lesions that may present although overall they are quite rare. If we are being pedantic one could group these lesions under the heading of NMSC too (since they are not MM), but in practice they have little in common with the other types of NMSC and they are usually referred to by their specific names. Students are not expected to know much about them.
Lymphomas of the skin can be either B or T cell and can present in a range of ways from a smooth topped solitary nodule through to a widespread scaly rash that might resemble psoriasis or even erythroderma. Some cutaneous lymphomas have a benign course and appear to be reactive in nature whereas others may reflect systemic disease or spread to other organs from the skin and be ultimately fatal. Diagnosis is difficult, and is based on suspicion and (often repeated) biopsy. Patients with cutaneous lymphoma need joint subspecialist dermatological and haematological care and long term follow up, as the natural history of many lesions is poorly described and the exact diagnosis may need to be revised over time.
Kaposi’s sarcoma (KS)
This is a herpesvirus 8 associated multifocal tumour of the lymphatic endothelium. The main groups affected in European populations are those with untreated HIV infection, those who are immunosuppressed such as is seen in organ transplants, and the elderly of Jewish or Mediterranean extraction. There is a more aggressive form that is endemic is Sub-Saharan Africa. KS commonly presents on the lower leg as a slow growing macule which becomes papular and nodular. Multiple foci may coalesce to form plaques. In its early stages some may resemble a bruise. Kaposi’s sarcoma may present elsewhere on the skin or mucosae including the mouth. If it is clinically possible to reverse the immunosuppression then most KS will regress.
Paget’s disease of the skin
There are two forms of Paget’s disease: that of the nipple, and extramammary Paget’s disease which commonly affects the genital area. They are both characterised by adenocarcinoma within the epidermis. In mammary (or nipple) Paget’s disease the (usually) female patient presents with a unilateral eczema like picture. In most cases there is an associated adenocarcinoma of the breast and treatment is that of the underlying breast carcinoma.
In extramammary Paget’s disease a similar histological picture is seen with spread of adenocarcinoma throughout the epidermis but only in a minority of cases can an underlying tumour in the rectum, prostate or bladder be found. The treatment is that of the underlying malignancy if one is found or, if not, then the cutaneous lesions are excised.
Merkel cell carcinoma
This is a neuroendocrine tumour that may or may not be derived from the Merkel cells in skin . It is mainly seen in the elderly and presents as a skin covered smooth nodule that may ulcerate. The prognosis is very poor, as the tumour metastasises early, and the usual treatment is excision with or without radiotherapy.
Dermatofibrosarcoma Protuberans (DFSP)
This is the commonest sarcoma of skin but is still very rare. Typical cases are middle aged adults or younger with a nodule or firm plaque close to the shoulder. DFSP may be mistakenly diagnosed as a scar, a keloid or a dermatofibroma. Metastasis is possible and excision is the treatment of choice.
Metastatic disease affecting the skin is uncommon but occurs. The tumours often present as smooth topped firm nodules in the skin. Melanoma may produce cutaneous metastases.
- Merkel cells are a cell type found in the epidermis. they are quite mysterious in terms of origin and exact function. They might be neural crest derived or be derived from the epidermis. They have a neuroendocrine phenotype and may be involved in sensation transduction. As stated above it is not clear that Merkel cell carcinomas are derived from Merkel cells although they share some morphological features.
- Name three risk factors for KS?
- What cell type is affected in KS?
- Name two common sites affected by Paget’s disease of the skin.
- Name a cutaneous sarcoma.
(answers are found at the end of the book)