Sclerosing orbital lesions: broadening the differential diagnosis of "idiopathic sclerosing pseudotumor"

Sclerosing orbital lesion
(the biopsy revealed it to be Erdheim-Chester disease)

Sclerosing lesions of the orbit can present a diagnostic conundrum. Often submitted with a differential diagnosis that includes idiopathic sclerosing pseudotumor, it is incumbent upon the pathologist to rule out other diagnostic possibilities before designating the lesion as idiopathic. In order to survey the range of diagnoses for such specimens, we searched over a 10-year period for specimens submitted to the University of Colorado pathology department which either clinically or pathologically raised the possibility of idiopathic sclerosing pseudotumor. We found 31 specimens (from 27 patients) that met criteria for review. The diagnosis for each of the 27 patients was confirmed after review of medical records. For 11 patients, a final clinicopathologic diagnosis of idiopathic sclerosing pseudotumor was rendered. The remaining diagnoses included: Wegener's granulomatosis (3), IgG4-related disease (2), reactive change to a prior procedure (2), schwannoma (2), sclerosed vascular malformation (2), Erdheim-Chester disease (1), non-Langerhans cell histiocytosis NOS (1), sarcoidosis (1), fibromyxoma (1), and thyroid eye disease (1).  Based on this institutional review, the differential diagnosis of fibrosing lesions of the orbit is broad, encompassing autoimmune, reactive, neoplastic, malformative, and endocrine disease. However, the most common final diagnosis remains idiopathic sclerosing pseudotumor.