Sir,

We report a rare presentation of peripheral primitive neuroectodermal tumor (pPNET) as an isolated conjunctival lesion.

Case report

A 23-year-old man presented to our clinic with a 1-month history of a painless, enlarging conjunctival lesion in his right eye (Figure 1a). The lesion was located at the lower temporal bulbar conjunctiva and was round, pinkish, and well-circumscribed on slit lamp biomicroscopy. He was diagnosed with left frontoparietal glioblastoma multiforme and had received subtotal tumor excision with radiochemotherapy as well as adjuvant Temozolomide two years ago. We excised the lesion and the histopathological report revealed conjunctival tissue with subepithelial diffuse infiltrates of tumor cells that possess medium-sized nuclei, fine chromatin, small nucleoli, and inconspicuous cytoplasm (Figure 2). Morphologically, it was a malignant tumor different from the previously diagnosed glioblastoma of the brain. Further immunohistochemical study showed positivity for CD99, CD56, neuron-specific enolase, and S-100 protein. Some were strongly positive for vimentin. All were negative for glial fibrillary acidic protein (GFAP, 6F2) and synaptophysin (SY-38). Re-excision was done weeks later, with no evidence of residual tumor histologically. Systemic survey showed no sign of metastasis. The oncologist suggested total surgical resection without adjuvant radiochemotherapy. The patient was followed for 18 months without local tumor recurrence (Figure 1b) or systemic metastasis.

Figure 1
figure 1

(a) Right eye external eye photo revealed a conjunctival mass located at the temporal side of the lower bulbar conjunctiva initially. (b) No sign of local tumor recurrence after excision with 18 months follow-up.

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Figure 2
figure 2

High-power magnification ( × 400) shows medium-sized nuclei, fine chromatin, small nucleoli, and inconspicuous cytoplasm. The tumor cells are focally arranged in rosette-like structures.

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Comment

PNET is a group of high malignant small round cell tumors arising from primitive neuroectodermal progenitor cells, which was classified as central PNET and peripheral PNET (pPNET). Batsakis et al1 divided PNET into the following three groups based on the tissue of origin: central nervous system PNET (tumors derived from the central nervous system), neuroblastoma (tumors derived from the autonomic nervous system) and pPNET (tumors derived from tissues outside the central and autonomic nervous system). pPNET was reported in a variety of locations, including the orbit and conjunctiva,2, 3 and has been considered as a highly aggressive tumor that typically metastasizes.1 A less propensity of metastasis and better prognosis for orbital pPNET was considered to be related to symptomatic disease, which led to early medical care seeking and early diagnosis.3 The only conjunctival pPNET case reported was a 16-year-old Caucasian boy who was treated with local wide excision and chemotherapy. No distant metastasis and no recurrence of tumor both clinically and radiologically for 29 months was reported.2 Here we reported the second case of conjunctival pPNET treated with only local excision, who has been in complete tumor remission for 18 months. Conjunctival pPNET as secondary malignancy was less likely because the secondary malignancy after Temozolomide treatment was mostly hematogenic.4 The oncologist suggested surgical resection only and close follow-up, which was similar to Chow’s experience for localized cutaneous and subcutaneous Ewing’s sarcoma family tumors.5

We reported a rare case of conjunctival pPNET who remained in tumor remission for 18 months following surgical excision only. A standard treatment strategy cannot be concluded from a single case report. Nevertheless, collaboration with specialists and timely diagnosis and treatment may be beneficial for a better outcome.