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Conjunctival melanoma is rare, accounting for just 2% of ocular malignancies.1 We present an unusual case of conjunctival melanoma with subsequent metastasis to the parotid gland. A diagnosis was made after fine needle aspiration cytology of the parotid gland was performed in light of the previous history.
A 79 year old white man presented to the eye clinic in September 1999. He had been noted 3 years previously to have a small inclusion cyst of the bulbar conjunctiva in his right eye, which he complained had increased in size and was becoming red and sore. Examination showed an inflamed pedunculated lesion 1 cm in diameter arising from the nasal limbal conjunctiva (Fig 1). The lesion was granulomatous and amelanotic. There was adjacent corneal opacity. Ocular examination was otherwise unremarkable.
The appearance of the lesion was felt to be unusual with a presumptive diagnosis of conjunctival malignancy. Excision biopsy with conjunctival autografting was performed.
Histology revealed a primary nodular malignant melanoma, at least 7 mm thick, composed of epithelioid sparsely pigmented melanocytes positive for S100 and vimentin immunostains. Excision was deemed incomplete.
The patient was referred for adjuvant treatment with cryotherapy. To date, there has been no sign of local recurrence.
In June 2001, the patient was referred by his general practitioner to the oral surgery service at the same hospital with a 6 month history of pain on the right side of his neck. He had also noticed some right facial swelling. Clinical examination disclosed a diffuse, firm mass over the lower pole of his right parotid gland, measuring 4 cm in diameter. There were no overlying skin changes.
Magnetic resonance imaging (MRI) of the head and neck showed a well defined lesion within the right parotid gland involving the deep lobe and the deeper portion of the superficial lobe. A few small lymph nodes were visible at several sites bilaterally but none appeared enlarged. Computed tomography (CT) of the chest, abdomen and pelvis revealed single nodules measuring 3–5 mm at both lung bases, which may represent lung metastases.
An orthopantomogram was normal, and fine needle aspiration (FNA) cytology was performed. This showed scattered lymphocytes and highly pleomorphic non-lymphoid malignant cells, some containing flecks of pigment (Fig 2). While these appearances alone would not allow definitive diagnosis of melanoma, in the clinical context they were sufficient to conclude that the parotid swelling was likely to be metastatic melanoma. This was confirmed on subsequent parotid excision biopsy, which revealed extensive involvement of the parotid nodes and parotid parenchyma, extending into the external jugular vein.
Malignant melanoma is a relatively rare tumour in the parotid gland, with most tumours representing metastasis from cutaneous head and neck primaries.2 Very occasionally, as in this case, the primary tumour is non-cutaneous in origin.
Conjunctival melanoma metastasising to the parotid has been noted in previous series,3 but remains rare. This case is unusual with respect to the initial size and appearance of the tumour, the previous history of a conjunctival cyst, and that definitive diagnosis of a metastatic lesion from a conjunctival primary was made by FNA. This method has been helpful in the diagnosis of other types of tumour in the parotid,4 and indeed in parotid melanomas of different origin.5 In this case, the patient’s previous ophthalmic history had been unknown to the maxillofacial surgeon managing the case, and the diagnosis only became clear during reporting of the cytology, when the FNA findings could be compared with previous histology. This illustrates the importance of exhaustive history taking and the value of a cohesive local histopathology service.