Orbital Nasal-Type Extranodal Natural Killer/T-Cell Lymphoma: An Ongoing Diagnostic Challenge Further Confounded by Small-Cell Predominance.

PURPOSE: To highlight the histopathologic diagnostic challenges of small-cell predominant extranodal nasal-type natural killer/T-cell lymphoma (ENTNKT) of the orbit.

METHODS

Retrospective chart review and histopathologic study with immunohistochemistry and in situ hybridization of 3 cases.

RESULTS

Three cases of ENTNKT presented to the Mass Eye and Ear emergency room as orbital cellulitis over 1 year. The first case was unusual in that there was a predominance of small cells, giving the ENTNKT the histopathologic appearance of a nonmalignant inflammatory process. This challenging case is juxtaposed alongside 2 other cases, which exhibited the more typical lymphomatous microscopic appearance.

DISCUSSION: ENTNKT can extend into the orbit from the adjacent sinuses or rarely arise primarily in the orbit. A diagnosis is typically made with a biopsy. Occasionally, however, the histopathologic diagnosis can be elusive when a predominance of small lymphomatous cells that are virtually indistinguishable from non-neoplastic inflammatory cells is present. Demonstration of CD56 positivity by immunostaining and in situ hybridization for Epstein-Barr virus are essential in confirming the diagnosis.

CONCLUSIONS

ENTNKT should be considered both in the clinical and histopathologic differential diagnoses of orbital infections and idiopathic inflammations (pseudotumor).