Retrobulbar granular cell myoblastoma.

Granular cell myoblastoma is a relatively uncommon lesion of debatable histogenesis, appearing as a small, solitary (but occasionally multiple) neoplasm and usually taking a benign course. The malignant counterpart has rarely been observed examples have also been found in virtually every organ or tissue of the body (Strong and others, I970), but only rarely in the orbit. Von Bahr (I938) reported an orbital granular cell myoblastoma situated in the region of the lacrimal sac. Dunnington (I 948) observed one in the upper part of the orbit leading to proptosis and exophthalmos and one in the region of the lacrimal sac. Dhermy, Morax, and Jolivet (I966) reported one in the eyelid of a 30-year-old woman. We have recently seen a retrobulbar granular cell myoblastoma leading to proptosis and exophthalmos in a Is-year-old boy. A 15-year-old mulatto boy was admitted to the Cancer Hospital of Paraiba, Brazil, with exoph-thalmos of 2 months' duration. Examination There was proptosis and exophthalmos of the right eye with marked palpebral oedema. X-ray examination showed no orbital bone involvement, and x-ray examination of the chest was within the normal limits. Operation A retrobulbar mass was found to be firmly attached to the optic nerve without invading it. The tumour, which was well-defined and of a firm and elastic consistency, was completely removed. It measured 5-4 x 3 0 cm. Microscopic examination There was a proliferation of large, round polygonal cells (Fig. i), with a small round vesicular to hyperchromatic nucleus and a pink cytoplasm with coarse granules (Fig. 2). The cells were arranged in clusters or cords and were occasionally separated by varying amounts of fibrous collagen tissue. Periodic acid-Schiff-positive cytoplasmic granules were seen, but there were no mitotic figures. In some fields the cytoplasmic granularity was condensed into amorphous acidophilic masses (Fig. 3), and nuclei with prominent acidophilic nucleoli were commonly seen.