An eccentric eye – Imaging findings in orbital sebaceous gland carcinoma

A 75-year-old man presented with gradually progressive painless swelling over the left upper eyelid with ptosis since eight months (Figure 1). There was no diplopia. It was a 4x3 cm non-tender, firm fungating mass. There was reduced visual acuity due to cataract. The ocular movements were normal and unrestricted.

On ultrasound, there was a 4.5x3.4 cm heterogeneously hypoechoic lesion with mild central vascularity (Figure 2). The lens was hyperechoic due to a cataract. There was no intraocular extension. On CECT, it was iso-hyperdense without fat or calcification. There was heterogeneous enhancement (Figure 3). There was no involvement of the bones of the orbital wall.

On MRI, it was a heterogeneously enhancing T1 hypointense, T2 hyperintense mass arising from the upper lid involving the skin, the orbicularis oculi muscle, and the superior orbital septa. The belly of the levator palpebrae muscle and adjacent loose connective tissue were spared; however, there was loss of fat planes with the tendinous insertion. The fat planes were maintained with the palpebral lobe of the lacrimal gland. There was diffusion restriction in the lesion (Figures 4a, 4b, 4c and 4d). The lesion was excised under general anaesthesia with lid reconstruction. Histopathological examination revealed high-grade malignancy with sebaceous differentiation suggestive of meibomian gland carcinoma (Figures 5a, 5b and 5c).

Sebaceous glands are holocrine glands consisting of meibomian glands of the tarsus, the glands of Zeis of cilia, and the glands of the caruncle [1,2]. Sebaceous gland carcinomas (SGCs) are rare but fatal lesions that can be mistaken for a number of other benign pathologies like chronic blepharoconjunctivitis, chalazion, and meibomianitis [3]. It has a high mortality rate. Hence, it is of great significance to differentiate these SGCs from other benign conditions [4].

SGCs have a multifocal origin with pagetoid spread, which makes them unique among eyelid malignancies. They are very slow-growing tumours commonly seen in the elderly population and with female predisposition; however, they have been reported in patients as young as 3.5 years old [5]. The upper eyelid involvement is very common due to the presence of larger number of meibomian glands.

Any patient presenting with a recurrent chalazion, especially with loss of eyelashes or with unilateral chronic blepharitis, should raise suspicion, and biopsy should be advised to rule out SGCs since delay in diagnosis leads to a poor prognosis [6–8]. The diagnosis is assisted by radiological investigations like MRI and CT scan, which help to assess the local and distant involvement. CT scan is the best modality to evaluate the presence of calcification and bony involvement. Ultrasound helps in evaluating the extent of the lesion and viewing the globe, especially the posterior chamber, in patients with cataracts. MRI paints an accurate picture of the soft tissue involvement due to its superior contrast resolution. SGCs are hyperintense on T2, and hypointense on T1 with heterogeneous enhancement [9]. They depict true diffusion restriction, due to the high cellularity.

Histopathology with immunohistochemistry, molecular biology and electron microscopy aid in the diagnosis of SGCs [6]. Surgical management is generally wide local excision, with wide resection margins due to the diffusely infiltrating nature of these lesions [10]. Lid reconstruction post-excision is equally important, the commonly used technique being Mohs micrographic surgery [3,8]. Radiotherapy might be used in patients with tumour size less than 10 mm and even in patients with T3–T4 stage if surgery is not feasible [11]. Radiotherapy is helpful in cases of involvement of the bones [3]. Prophylactic neck irradiation reduces the risk of nodal recurrences [11]. Due to delays in diagnosis and treatment, the mortality rate is 10%, and 25% in the case of metastases.

Poor prognostic factors are upper or both eyelid involvement, tumour size more than 10 mm, symptoms more than six months, poorly differentiated tumours, infiltration into blood vessels/lymphatics, orbital extension, multi-centric origin, and pagetoid spread [3,12].

The tumour is staged according to the TNM classification as per the AJCC [13].