Granular cell tumour: a rare caruncle lesion

Granular cell tumour is a benign neoplasm of a Schwann cell in origin.¹ Rarely this tumor arises in the orbit, skin of the eyelid, palpebral conjunctiva, lacrimal sac, caruncle, and inferior oblique muscle.² We report a case of granular cell tumour of the caruncle in an adult patient with mechanical ectropion and immunohistochemical features of this lesion.

Case report

A 72 year old male patient was evaluated for ectropion of the right lower eyelid, 2 months in duration. Examination revealed a 1 cm, firm, movable, reddish caruncle mass in the right eye associated with ectropion (fig 1A). Computed tomography of the orbit revealed a hyperdense lesion located at the anterionasal side of the globe (fig 1B), and the patient underwent incisional biopsy.

Figure 1 (A) Clinical photograph revealing a caruncle mass in the right eye. (B) Axial section of a computed tomographic scan shows a hyperdense lesion located in the caruncle area.

Histopathology of the mass revealed sheets of large polygonal cells with relatively small, bland appearing nuclei without prominent nucleoli and copious amounts of brightly eosinophilic granular cytoplasm (fig 2). There was no mitotic activity or necrosis. The mass contained a sparse lymphoid infiltrate made up of CD3 and CD20 positive lymphocytes and stained for both kappa and lambda immunoglobins. The large polyglonal tumoral cells were positive for S‐100, CD68, and inhibin‐α (fig 2C and D). Ki‐67 stain showed a low mitotic index. Histopathological diagnosis was granular cell tumour. Subsequently, the patient underwent total excision of the lesion that revealed the above histological features. Follow up examination at 4 months showed no recurrence.

Figure 2 Caruncle revealing eosinophilic mass and lymphocytic infiltration (A). Higher magnification shows eosinophilic cells with abundant granular cytoplasm and small oval nuclei (B). The neoplastic cells stain positive with CD68 (C) and inhibin‐α (D).

Comment

This case shows that granular cell tumour, although rare, can present as an isolated caruncle mass. Clinically, because of their smooth yellowish pink or red appearance they may mimic other caruncular tumours such as sebaceous tumours and oncocytoma. However, on histopathological examination, the diagnosis of granular cell tumour can often be made on haematoxylin and eosin sections as a result of its characteristic morphological features. Nevertheless, immunohistochemical studies may be needed to rule out other lesions such as oncocytoma. Immunohistochemically the tumour cells are positive for S‐100 and CD68. Expression of S‐100 in the granular cells supports the neural origin of this tumour.³ Positive stain with CD68 (a macrophage marker) can be explained by the intracytoplasmic accumulation of phagolysosomes and does not reflect a histiocytic origin.⁴ Additionally, it has been shown that the granular cells are also positive for inhibin‐α.³ Although inhibin‐α has been demonstrated to be strongly supportive of a granular cell tumour, the relation between this expression and pathogenesis of the granular cell tumour is unclear.³ Histologically, the present case has shown typical features of granular cell tumour on light microscopy and by immunohistochemical staining.

The majority of granular cell tumours are benign. Atypical histological features noted in malignant granular cell tumours include necrosis, increased mitotic activity (Ki‐67 proliferative index), high nuclear/cytoplasmic ratio, and nuclear pleomorphism. Our case did not show these atypical features.

Granular cell tumour should be included in the differential diagnosis of an asymptomatic caruncle mass that may cause secondary mechanical ectropion, as in our case. In the majority of cases, these lesions represent a benign isolated tumour. Surgical excision is the treatment of choice with minimal or no potential of recurrence.