Axillary intranodal palisaded myofibroblastoma, a rare tumour at an unusual site, with literature review

Intranodal palisaded myofibroblastoma (IPM) arising in the axilla is an extremely rare, benign mesenchymal tumour. It is believed to originate from myofibroblast or smooth muscle cells and exhibits specific histopathological features. While there have been occasional cases of recurrence, no malignant transformation has been observed. We describe the case of a 35-year-old male presenting with an axillary mass. Histopathology revealed a tumour with a pseudo-capsule that contains compressed lymphoid tissue with spindle cells arranged in a palisade-like pattern and extravasation of red blood cells within the spindle cells. Additionally, amianthoid fibres and fuchsinophilic bodies are present. Immunohistochemical analysis typically was positive for SMA and cyclin D1, with a low proliferative index (Ki67 of <1%). The diagnosis was intranodal palisading myofibroblastoma. Only two cases of IPM in the axilla have been previously reported. Pathologists should keep this rare entity with characteristic histopathological findings in mind when reporting such tumours at an unusual site.