Nodal follicular dendritic cell sarcoma of the axilla with brachial plexus palsy

Axillary mass lesions have a wide differential diagnosis however reactive lymphadenopathy and skin lesions such as sebaceous cysts comprise the majority. In 1986 Monda reported the first case of a nodal follicular dendritic cell sarcoma arising from lymphatic follicular dendritic cells. Since then approximately 500 cases of this relatively novel tumor type have been described. The nodal form occurs most commonly in the cervical region however an extra nodal form has been described commonly occurring in the liver and spleen. Isolated reports of very rare locations include the mediastinum, tonsils, hepatogastric ligament and urinary bladder. We report a 34 year old HIV negative patient whom presented to our unit complaining of a progressively increasing right axillary mass associated with paresthesia of the right hand in a median nerve distribution. Examination of her right axilla revealed a large, non-tender, firm, fixed mass with no overlying skin changes. Neurological examination revealed wasting and weakness of the thenar eminence of the right hand with weakness of thumb apposition 3/5. An MRI revealed a 10 cm by 10 cm heterogeneous well circumscribed mass lesion extending deep into the axilla. Due to the patients progressive neurology she was taken to surgery under neurophysiological monitoring for a combined orthopedic neurosurgical procedure where the median cord of the brachial plexus was found draped over the superoposterior part of the lesion. Post operatively she had resolution of the paresthesias in her right hand and at her three month review her left thumb showed improvement in power 4/5. Histological analysis revealed the tumor to be a nodal follicular dendritic cell sarcoma. A metastatic screen was negative. In conclusion misdiagnosis of an isolated painless axillary mass as a lipoma, as occurred in our patient, allowed this malignancy to reach considerable size. The progressive neurology provided the red flag for urgent surgical intervention.