Cutaneous histiocytoid carcinoma can occur as a primary tumor of the periocular region. Morphologically similar histiocytoid carcinomas arising as primary tumors of the breast have a predilection for orbital metastases. They can occasionally contain regions with prominent vacuolated cytoplasm and minimal nuclear atypia, which mimic benign histiocytic lesions. Differentiating nonneoplastic, primary neoplastic, and metastatic histiocytoid lesions involving the periorbita can be challenging for both the clinician and the pathologist, and this distinction has management implications. Herein, we present 3 cases to illustrate the challenges of diagnosing periocular histiocytoid carcinoma.

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Background: Patients with xeroderma pigmentosum (XP) are strongly predisposed to the development of numerous cutaneous cancers. However, the extent of ocular pathology in these patients has not been adequately studied. Methods: We conducted a retrospective study of tumors involving the ocular surface and ocular adnexa from 6 XP patients. Histopathological evaluation and immunohistochemistry was performed using antibodies directed against the most common mutated proteins in XP (XPA, XPC, and XPD). Results: Patients included 4 males and 2 females with a mean age of 20.8 years (range 10-31) who met the clinical criteria for XP and were found to have a total of 13 neoplasms involving the ocular surface and adnexal skin; 6 squamous cell carcinomas (SCC), 3 cases of conjunctival intraepithelial neoplasia, 2 malignant melanomas, 1 basal cell carcinoma, and 1 atypical fibroxanthoma. Complete XPD loss was present in two tumors from 1 patient, suggesting a germline defect, and in the invasive component of an SCC from a second patient, suggesting a somatic alteration. No clear pattern of loss for XPA or XPC was evident. Conclusions: Our study outlines our early experience with the pathology of ocular neoplasms in XP patients. These findings deserve further exploration with genetic studies and additional patients.