The patient was assessed for pain and swelling in the left ankle 12 months previously, with no report of trauma. After imaging, he underwent a bone biopsy of the lateral aspect of the calcaneus using a core needle.

The biopsy revealed an undifferentiated small cell neoplasm, with immunohistochemical staining for CD45+, CD20+ and Ki67 80%, compatible with diffuse large B-cell non-Hodgkin's lymphoma.

The patient was started on onco-hematological treatment and did not require surgery.

Follow-up was carried out using PET-CT and he finished treatment after around 7 months, with no local complaints.