A single-centre experience of secondary cutaneous tumours with special reference to precocious metastases.

Background: Secondary involvement of skin by tumour comprises 2% of cutaneous neoplasia, in a small proportion of cases serving as the primary manifestation of occult disease.

Methods: Cases of cutaneous metastases (CM) were retrieved from our pathology files between 2013 and 2018 and clinical and histopathological data reviewed.

Results: There were 159 cases (median age 70). A majority of clinical presentations comprised isolated, papulonodular lesions. While the anatomic distribution of lesions often bore a proximate relationship to the primary tumour, distant sites of involvement were frequently encountered. Melanoma gave rise to the greatest number of metastases, followed by tumours of the breast, colorectum, and squamous cell carcinoma. In six cases (3.8%), CM served as the presenting feature of occult malignancy. These patients presented at a more advanced age and with distant sites of involvement. The microscopic features of CM include nodules, nests, and cords or single cell infiltrates typically in deeper compartments in the absence of overlying epidermal or adnexal precursor lesions.

Conclusions: CMs are a frequent development in the natural history of melanoma and breast tumours. In practice, a wide spectrum of tumours may give rise to CM and a small proportion more importantly, signal the existence of previously unknown neoplasia.