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It is a non-Langerhans cell histiocytic lesion that typically affects adults. According to the revised classification of histiocytic disorders, solitary reticulohistiocytoma (SRH) is listed under the C group (xanthogranuloma family).
Both cases were aged 21 years, females, and medically free. The first patient presented with an ovoid, salmon-colored, inferonasal limbal mass with minimal encroachment on the peripheral cornea. The lesion started 2 months before the patient's presentation. The clinical appearance suggested a lymphoid lesion.
The second patient had a history of a slowly growing mass covering the left cornea for which she underwent a keratoplasty, but the excised lesion was not available for microscopic examination. However, clinical examination of the same eye demonstrated a “large, polypoid, fatty-like growth covering the lateral aspect of the cornea with encroachment on the adjacent limbus.” The lesion of the first patient was excised with shaving of the peripherally involved cornea, whereas the lesion of the second patient was excised with an additional lamellar keratoplasty. Recurrence was not seen in the first patient 10 months after the excision. The follow-up evaluation of the second patient was not reported.
Our patient is an 11-month-old boy, who is considered the youngest and the only boy of previously reported SRH cases. He was brought by his parents with a complaint of right eye swelling that developed after a trauma by a finger 3 months before the presentation. Examination revealed an elevated, whitish, vascularized, nasal limbal lesion that extended subconjunctivally and into the peripheral corneal stroma. The lesion was measuring 10 mm in its largest diameter. The patient did not have a systemic disease or similar lesions involving the skin. The lesion was excised with a corneal patch graft. The patient was followed for 3.6 years without recurrence of the disease. However, his last documented vision was 20/200 due to significant astigmatism and the resulting anisometropic amblyopia. Clinical photograph of the lesion was not available.
The excised tissue showed confluent aggregation of histiocytic cells with large ovoid reticulated nuclei and prominent nucleoli. No mitoses or atypia were present. The histiocytic cells showed abundant eosinophilic cytoplasm that had a finely granular to glassy appearance. The majority of the cells were mononuclear, but there were also few cells that were multinucleated (Fig. 1). No Touton or foreign body giant cells were present in the whole submitted tissue despite lengthy scanning of all histologic sections. Small numbers of empty vesicles, suggesting lipid accumulation, were scattered throughout the lesion, but this did not appear to be a significant characteristic of the lesion. Occasional cells demonstrated a smaller amount of more intensely eosinophilic cytoplasm and homogenous-appearing basophilic nuclei, which might have represented younger histiocytic cells.
There was extensive capillary proliferation throughout the lesion with enlarged reactive-appearing endothelial cells, and numerous chronic inflammatory cells present between the large histiocytic cells, consisting predominantly of lymphocytes. Plasma cells and moderately numerous eosinophils were present with apparent degranulation of some of the eosinophils as well. There was a general sparing of the overlying connective tissue and epithelium from involvement by the histiocytic infiltration except for small numbers of histiocytes that were present around superficial vessels within the connective tissue layer. The histiocytic cells did not express reactivity to the S-100 protein stain.
The clinical differential diagnoses of SRH of the ocular surface include dermoid, dermolipoma, nodular scleritis, pyogenic granuloma, foreign body granuloma, pterygium, lymphoproliferative lesions, and neoplasia. The histopathologic differential diagnoses of SRH of the ocular surface include juvenile xanthogranuloma, amelanotic malignant melanoma, and Langerhans cell histiocytosis. Langerhans cell histiocytosis cells react strongly to the S-100 protein in contrast to the cells of reticulohistiocytoma. The morphology of the lesion, the absence of Touton giant cells, the cytologic appearance of the mononuclear/multinucleated non-Langerhans histiocytes, and the abundant eosinophilic cytoplasm, along with the predominant lymphocytic infiltrate, allowed us to differentiate SRH from juvenile xanthogranuloma. This diagnosis was favoured by 2 ophthalmic pathologists with long experience in the field. The absence of high nucleocytoplasmic ratio and immunoreactivity to the S-100 protein were against the diagnosis of amelanotic melanoma.
Cutaneous SRH may resolve spontaneously but surgical excision is classically curative.
There are no guidelines for work-up and treatment of SRH. All corneo-limbal reticulohistiocytomas, including our case, were excised surgically. An additional keratoplasty was needed in 2 cases in which the corneal stroma was deeply involved. Recurrence was not documented in any of the cases.
Footnotes and Disclosure
The authors have no proprietary or commercial interest in any materials discussed in this article.
Reticulohistiocytoma (solitary epithelioid histiocytoma): a clinicopathologic and immunohistochemical study of 44 cases.