Rare skin cancers

Merkel cell carcinoma (MCC)

Merkel cell carcinoma (MCC) is an extremely rare malignant primary neuroendocrine carcinoma of the skin. Its aetiology is largely unknown; it develops more frequently in immunocompromised individuals. Recently it has been linked to the presence of Merkel cell polyomavirus (MCV). Body parts exposed to the sun (head, neck, limbs) are the most common locations of MCC. The main clinical symptom is a fast-growing, painless dark-red or bluish nodule. Radical resection including the sentinel lymph node and a safe margin is the choice of treatment. Radiotherapy is indicated when regional lymph nodes are affected, chemotherapy and biological therapy (multikinase inhibitors, mTOR inhibitors) can also be indicated in children and adolescents. The prognosis is poor in adults, and mortality rates are higher than in malignant melanoma; prognosis and mortality rates in children are unclear due to an extremely rare occurrence.

Squamous cell carcinoma (SCC)

Until recently, squamous cell carcinoma (SCC) was practically non-existent in children and adolescents. Currently, its incidence is expected to grow particularly in individuals with a genetic predisposition (epidermolysis bullosa) who live to the adolescence or young adult age, as well as in children with genodermatoses and an excessive sensitivity to sunlight (xeroderma pigmentosum). These patients usually develop multifocal, deep-penetrating and aggressive SCC which form early metastases and have a poor prognosis. The tumour is usually localised in body parts exposed to sunlight (head, neck, limbs). In the long term, squamous cell cancer also presents a risk for paediatric patients who underwent the transplantation of an organ or of haematopoietic stem cells. However, pale skin (phototype I and II) and sunlight in predisposed individuals remain to be the most important risk factors. Surgical treatment with radical resection is the choice of treatment, and biological therapy might be indicated for advanced SCC.

Basal cell carcinoma (BCC)

Basal cell carcinoma (BCC) is extremely rare among children and adolescents. It usually develops in individuals with genetically determined conditions (genodermatoses) – xeroderma pigmentosum, naevoid basal cell carcinoma syndrome, sebaceous naevus, Gorlin syndrome, or Bazex syndrome. It can also occur in patients with albinism or those who underwent radiotherapy. Aetiology is unknown for sporadic BCC. An association between BCC and the inactivation of tumour-suppressor gene located at the 9q22 chromosome has been described. BCC usually manifests itself as a reddish skin morph, often located in the facial area. The average age at the time of BCC manifestation is around 7.5 years. Surgery is the choice of treatment. It is arguable whether the clinical behaviour of BCC is more aggressive in children than in adults. The prognosis is usually limited by the genetic background.