The risk of cutaneous squamous-cell carcinoma (skin cancer) recurring or spreading around the body is increased when tumour thickness exceeds 6•0 mm or when desmoplastic growth occurs. Location at the ear or immune suppression also increase the risk of the cancer spreading, according to research which will be published in The Lancet Oncology.

Squamous-cell carcinomas (SCC) are among the most common cancers capable of metastasis. Dr Kay Brantsch and Professor Helmut Breuninger, Department of Dermatology, Eberhard Karls University, Tübingen, Germany, and colleagues analysed the key factors predicting metastasis and local recurrence in skin SCC.

The investigators looked at 615 patients, all of whom had surgery on skin SCC between 1990 and 2001 in a single centre in Germany. The tumours extracted were given complete 3D histological examination, and tumour thickness, horizontal size, body site, histological differentiation, desmoplastic growth, history of multiple SCC, and immunosuppression in the patient were all recorded. Time to metastasis or recurrence was also measured, defined as the time from date of diagnosis of the primary tumour to the date of diagnosis of metastasis or local recurrence.

A total of 615 patients aged between 27 and 98 years were assessed during a median follow-up of 43 months. In this time, 26 patients (4%) experienced metastases and 20 (3%) experienced local recurrence. Tumours 2•0 mm or less in thickness did not metastasise. However, metastases occurred in 12 (4%) of 318 tumours between 2•1 mm and 6•0 mm thick and in 14 (16%) of 90 tumours with a thickness greater than 6•0 mm. The researchers determined that the key risk factors for metastasis were increased tumour thickness (nearly five-times increased risk); a suppressed immune system (4.3 times increased risk); location at the ear (3.6 times increased risk); and increased horizontal size (over double the risk). The risk of local recurrence was dependent on increased tumour thickness (six times the risk) and desmoplasia (16 times the risk).

The authors say: “Only SCC greater than 2•0 mm in thickness are associated with a significant risk of metastasis. Tumours greater than 6•0 mm are associated with a high risk of metastasis and local recurrence. Desmoplastic growth is an independent risk factor for local recurrence.”

They suggest that high-risk patients should be followed-up every three or four months by clinical investigation and by ultrasound of the regional lymph nodes for four years, although they concede data will need to be produced to show the benefit of this for patients. They say this follow-up has been approved for patients with melanoma—and patients with early lymph-node metastases have a significantly better prognosis than more advanced nodal disease, strongly arguing in favour of a structured follow-up process and/or sentinel lymph node biopsy.

The authors also argue in favour of changing the current Tumour Node Metastasis (TNM) staging system, which at the moment includes horizontal tumour size, involvement of extradermal skin structures, and degree of cell differentiation. They conclude: “On the basis of these findings, we believe that a revision of the current TNM staging system is needed for accurate patient staging, patient management in daily practice, and studies on this increasingly important tumour.”