We present a 30-year-old man, with no medical or surgical history of interest, who consulted for a left latero-cervical tumour of several months' evolution; the patient reported night sweats in recent months as the only noteworthy finding in the anamnesis.
Examination revealed a tumour measuring approximately 5x5cm in diameter medial to the lower third of the sternocleidomastoid muscle (SCM) with an elastic consistency, poorly defined, not adhered to deep planes or skin, whose size did not vary with postural changes, non-pulsatile, and with negative auscultation.
A computerised tomography (CT)-guided puncture was requested, which was reported as lymph node cellularity with indeterminate changes that could not be cytologically typed, recommending a viral serology study.
The CT scan with intravenous contrast showed a homogeneous, solid, well-defined mass measuring 5x7 cm, located in the left cervical vascular space, compressing the left internal jugular vein, behind the MCE, with moderate contrast uptake and some adjacent lymphadenopathy. There was no hyperenhancement suggestive of carotid glomus. The radiological differential diagnosis included lymphoproliferative process, neurogenic tumour or mesenchymal tumour.

Under general anaesthesia a left supraclavicular horizontal incision and section of the ECM muscle at this level was performed to obtain adequate exposure. A 5x7 cm tumour of congestive appearance was found, hard with intense peripheral vascularisation that made its dissection difficult; the tumour presented a plane of separation with the vascular space. The clinical appearance at the time of surgery impressed the authors as a vascular tumour.

Pathological examination of the specimen revealed a lymph node with preserved architecture and a marked increase in the number of lymphoid follicles and positivity for immunohistochemical markers (CD20+CD10+, bcl2-). Characteristically, the germinal centres showed hyaline material, some vessels and onion-layered arrangement of the lymphocyte crown.

The number of plasma cells (CD138) were in the normal range and showed no restriction for immunoglobulin light chains (kappa and lambda).
The molecular study did not detect the presence of human herpes virus type 8 (HHV 8) by PCR.
A thoraco-abdomino-pelvic CT scan was performed, which was normal. Complete blood tests, immunology and serology were normal.
These findings represent the localised form of lymphoid angiofollicular hyperplasia or Castleman's disease, hyaline-vascular variant.