Carcinoid presenting as extrinsic eye muscle metastasis

Abstract

Editor, Orbital carcinoid metastases are uncommon, especially as presenting signs, and may have a different appearance on magnetic resonance imaging (MRI) than other metastatic orbital tumours (Braffman et al. 1987). We present a case of carcinoid metastasis to an extrinsic eye muscle from a primary midgut tumour. In March 2007, a 69-year-old man presented with a 2-week history of pain behind his right eye. Examination revealed a 4-mm right eye proptosis (Hertel 27/23) and vertical diplopia caused by the restriction of right eye elevation. Visual acuity and visual fields were normal. Orbital computed tomography (CT) showed a well-defined, olive-shaped mass measuring 24 × 13 × 15 mm involving the oblique superior muscle. It dislocated the medial rectus caudally and slightly compressed the optic nerve. On MRI the tumour was isosignalling with muscle on T1 and had a marked low signal on T2, suggesting idiopathic orbital inflammation/myositis or lymphoma (Fig. 1). Magnetic resonance imaging showing a 24 × 13 × 15 mm orbital mass in the medial portion of the right orbit (arrow). Chest X-ray and extensive biochemical analyses were normal. Orbital fine needle aspiration biopsy showed tumour cells of presumed neuroendocrine origin. The patient underwent combined lateral and anterior orbitotomy and the oblique superior muscle including the tumour was removed. Histopathological examination and routine immunohistochemical staining for synaptophysin and chromogranin A confirmed the diagnosis of a carcinoid tumour (Fig. 2). Microphotograph showing nests of moderately atypical tumour cells of (A) presumed neuroendocrine origin, (B) tumour cell immunoreactivity for synaptophysin and (C) chromogranin A. (Haematoxylin and eosin; original magnification × 100.) On subsequent investigation with octreotidscintigraphy, together with 5-hydroxyindole acetic acid (5-HIAA) and chromogranin A analyses (both significantly elevated), a primary carcinoid tumour was found in the small intestine with multiple lymphatic gland, liver and gall bladder metastases and a suspected metastasis to the pancreas. The patient is presently recovering from ileoectomy, mesenteric lymph node dissection and cholecystectomy. He is under treatment with Sandostatin® (Novartis Pharma AG, Basel, Switzerland) and waiting for embolization of the liver metastases. No adjuvant orbital radiotherapy has been given as the metastasis was well defined and a 6-month follow-up with orbital CT showed no local recurrence. The patient’s ocular motility is good except for diplopia at downward and left gaze. Carcinoid tumours originate from enterochromaffin cells found mainly in the gastrointestinal and bronchial tracts, but can also be found in, for example, the ovary, breast, testis and biliary system. Common sites of metastases are regional lymph nodes, liver, lung and peritoneum. The tumour cells are able to synthesize and release substances such as serotonin, histamine and prostaglandins. Carcinoid syndrome occurs when liver and lung metastases have developed and vasoactive substances are no longer degraded. It is characterized by flushing, diarrhoea, tachycardia and bronchospasm. Treatment includes surgical resection of the primary tumour, surgical treatment or embolization of metastases and pharmacotherapy to reduce the vasoactive peptides (Fox & Khattar 2004). The 5-year survival rate of localized midgut carcinoid is 62.2%, but this deteriorates to 48.2% if distant metastases are present (Modlin et al. 2003). Orbital carcinoid metastases are rare, representing only 0.4% of total metastases to the orbit, which in turn constitute 10% of all orbital neoplasms (Goldberg et al. 1990). A case series from Moorfields Eye Hospital reported 13 cases between 1967 and 2004, of which all but four featured a previously known primary tumour and only two presented with orbital pain (Mehta et al. 2006). In cases such as that presented here, in which the tumour has unusually low signalling for orbital metastases on T2-weighted MRI (in agreement with Braffman et al. 1987), it is important to remember carcinoid as a possible differential diagnosis even when the patient has no intestinal complaints and no symptoms of carcinoid syndrome. Histopathological examination is, of course, of vital importance in establishing a correct diagnosis in order to enable medical evaluation and treatment of the primary tumour and metastases.