Angiosarcoma of the parotid gland with a t(12;22) translocation creating a EWSR1–ATF1 fusion: a diagnostic dilemma

We present a case of a malignant tumour of the parotid gland, originally thought to represent metastatic melanoma (of unknown primary), later reclassified as malignant melanoma of soft part/clear cell sarcoma (MMSP/CCS) on the basis of the presence of a EWSR1–ATF1 gene fusion. Further immunophenotypic studies demonstrated vascular differentiation in support of a diagnosis of angiosarcoma. Although extraordinarily rare, angiosarcomas of the parotid gland have been described; while MMSP/CCS of the parotid has not been documented, EWSR1 rearrangements have never been demonstrated in angiosarcoma. This case therefore provides an example of the way in which morphological findings must be integrated to provide the appropriate pathological diagnosis. A 72-year-old otherwise healthy woman presented with a 6-week history of a rapidly enlarging mass of her right jaw, with associated facial nerve paralysis. A head and neck CT scan showed an enhancing 3.5×2.6×4.0 cm mass with ill-defined margins and a somewhat spiculated appearance in the right parotid gland, which was subsequently excised. Grossly, an ill-defined nodule with extensive haemorrhage, measuring 4.7× 2.4×2.4 cm, was present. Microscopic examination showed a pleomorphic malignant neoplasm that appeared to arise in an intraparotid lymph node. The tumour invaded adjacent skeletal muscle and adipose tissue and had vascular-like spaces. The tumour cells had epithelioid, spindle and focal rhabdoid morphology (figure 1). No melanin pigment was present. The tumour cells in many areas grew around vessels with a characteristic peritheliomatous pattern, and areas with Azzopardi effect were also seen. Figure 1 (A) Low-power view (4 ). A malignant neoplasm is seen with infiltration into the parotid parenchyma. (B) Some areas show a clear spindle cell component. (C, D) High …