This is the first case report of dermatofibrosarcoma protuberans (DFSP) arising in a patient with X-linked agammaglobulinaemia (XLA). XLA is the prototypic genetic disorder resulting in a lack of antibody production. Mutations are found in the Btk gene, which results in arrest of B cell development from pro B cells to pre B cells and subsequently to mature B lymphocytes.1 These patients are prone to recurrent infections without replacement immunoglobulin but are generally not at increased risk of malignancy. DFSP is a slow growing cutaneous tumour that has been reported previously with HIV infection and post-renal transplantation, but not with antibody deficiency.

Case report

A 46-year-old man, known to have XLA, presented in 2001 with a painless cystic subcutaneous swelling over the proximal interphalangeal joint of his right little finger. The swelling had gradually been increasing in size over the previous year. Plain radiographs of the area were normal. The lesion was excised and histology showed a subcutaneous nodule composed of densely packed spindle cells with tapering nuclei. Collagen was focally seen between the cells but there were no giant cells or foamy histiocytes, although mitoses were identified. The findings were those of a DFSP, which had been incompletely excised. Subsequent immunohistochemical staining demonstrated the tumour was CD34 positive and factor XIIa negative.

The lesion recurred 4 months later and was re-excised. However, histology, showed widespread recurrence and the finger was subsequently amputated with clear resection margins.

This man had originally been …