Malignant rhabdoid transformation of a longstanding, aggressive, and recurrent orbital angiomyxoma

Abstract

A 47-year-old woman presented with a medial orbital tumor initially diagnosed as either a myxoid neurofibroma or myoepithelioma. Over 30 years the tumor recurred seven times and was serially debulked. Careful histopathologic analysis coupled with immunohistochemical studies performed on the last two biopsies established the rare diagnosis of a locally aggressive angiomyxoma (because of its local infiltrative growth) with myofibroblastic features (smooth muscle actin and calponin positivity and desmin negativity). The last recurrence manifested at a shorter interval than the earlier ones, suggesting an accelerating clinical course. By this late stage there was complete blindness, a frozen globe, and extreme, unmeasurable proptosis accompanied by massive chemosis and eyelid fullness. An exenteration was performed, and the orbital contents contained a persistent angiomyxoma, but additionally, another cellular population had emerged-mitotically active cells with a malignant rhabdoid phenotype (round shape, cytoplasmic hyaline/globoid inclusions composed of whorls of compact vimentin filaments as well as epithelial membrane antigen and focal cytokeratin positivity). This is the first orbital case of a rhabdoid transformation of a benign orbital mesenchymal tumor. Shortly after the exenteration, multifocal metastases, notably to the lungs, were found, leading to the introduction of chemotherapy, which was discontinued because of non-responsiveness of the tumor and patient intolerance. After 1 year of follow up, the patient is still alive, but has persistent active disease with widespread metastases and a guarded prognosis.

Keywords: INI1; angiomyxoma; cytokeratin; orbit; rhabdoid tumor; vimentin.