ANSWERS

From questions on page 137

1. What is the differential diagnosis of an orbital mass in this age group?

The primary differential diagnosis of a rapidly enlarging orbital mass in this age group is rhabdomyosarcoma, which may present with or without the inflammatory features of orbital cellulitis, dacyroadenitis or idiopathic orbital inflammation. Dermoid cysts typically arise in the superotemporal location but commonly present early in the first decade of life and appear cystic radiologically. Granulomatous conditions which may involve the orbit include tuberculosis, sarcoidosis and Wegener granulomatosis.

2. Describe the ct findings in figs 2, 3

Figure 2 is a transverse section through the orbit demonstrating a solid extraconal orbital mass extending to 12 mm behind the posterior pole of the globe. Figure 3 is a coronal section with the mass occupying the whole of the supero-temporal orbit.

3. How would you manage this patient?

An urgent tissue diagnosis is mandatory in such cases in order to rule out malignancy. In this patient, two sizeable incision biopsy specimens were removed from a hard, rubbery and relatively avascular lesion via a transdermal approach.

Histological examination revealed necrotising granulomatous inflammation of the lacrimal gland with no caseation (fig 4). Histochemical staining for acid-fast organisms (Ziehl Neilson and Wade-Fite), …