Orbital Lobe and Palpebral Adenomas of the Lacrimal Gland Behave as Distinct Entities.

Abstract

To assess whether orbital lobe and palpebral adenomas of the lacrimal gland are biologically similar, based upon a comparison of the age at presentation and at first symptom. The size of the excised tumor in the 2 groups is also examined and considered in relation to age at surgery. Review of clinical details and histopathology reports for patients with biopsy-proven lacrimal gland pleomorphic adenomas, under the care of Moorfields Eye Hospital. The age at presentation and at earliest symptoms were calculated for each patient. Where available, estimates of tumor volume were obtained from the 3 orthogonal measurements taken during histopathological examination. One hundred eighty-seven patients (100 male patients; 53%) presented at an average age of 48 years (median, 46.8; range, 11-88): the average age for 144 patients with orbital lobe tumors (mean, 48 years; median, 47.8; range, 11-88) was similar to that for 43 patients with palpebral tumors (mean, 46 years; median, 46.8; range, 24-81) (p = 0.45). The average age at first symptom(s) in the 2 groups is similar (orbital 45 years, palpebral 44 years; p = 0.63). In contrast, there is a very highly significant difference in estimated tumor volumes, with the mean for orbital lobe pleomorphic adenomas being 5.4 ml (median, 4.9 ml; range, 1.5-13.6) and that for palpebral being 0.91 ml (median, 0.7 5 ml; range 0.11-3.61) (p = 1.42 × 10-25). As expected, excised palpebral adenomas-readily palpable in the eyelid-are very much smaller than orbital lobe tumors, that tend to be impalpable. If pleomorphic adenomas in the 2 locations were biologically identical, they should arise at the same time and have similar growth rates-which would mean that orbital pleomorphic adenomas ([PAs] being, on average, 6 times the size of palpebral PAs) should present several decades later. The age at presentation and age at first symptom are, however, almost identical in the 2 groups. These observations provide incontrovertible evidence that, in their biological behavior, palpebral and orbital PAs are distinct entities-either arising at different ages (with orbital tumors arising much earlier in life) or having different growth rates (palpebral PAs being slower).