Hibernoma of cervical region

A 42 year old male presented with swelling in the right posterior cervical region for a period of 2 months. Palpation revealed a soft, non tender, mobile swelling measuring 2 x 1 cms. An elective excision biopsy was performed. Gross examination showed a yellow to pale brown soft mass. On microscopy, a well circumscribed tumour composed of two populations of cells(uni-vacuolated white adipocytes and multivacuolated brown adipocytes) was seen (Fig. 1). Gradual transition between the two populations was seen (Fig. 2). The white adipocyte cells with clear cytoplasm and peripheral nucleus were seen in the periphery of tumour. The brown adipocyte cells with granular eosinophilic multi-vacuolated cytoplasm and central round vesicular nucleus were seen in the central areas of tumour (Fig. 3). No atypia or necrosis or mitosis was seen. With the morphological features a diagnosis of hibernomabenign tumour of brown fat was made.