Extranodal natural-killer/T-cell lymphoma, nasal type: An immunomorphological study from a regional cancer institute in India

Introduction: Extranodal natural-killer/T-cell lymphoma, nasal type (ENKTL), is a rare, aggressive, predominantly extranodal non-Hodgkin lymphoma (NHL) of putative natural-killer (NK) cell and rarely T-cell origin, always associated with Epstein-Barr virus (EBV) infection and characterized by highly distinctive histopathological features with predilection for the upper aerodigestive tract. While the nasal cavity is the prototypical site, less frequently extranasal ENKTL can also occur. The objective of this case series is to study the immunomorphological features of ENKTL from a tertiary cancer centre as the data are sparse from India despite it being a distinct entity with characteristic clinicopathological features. Methods: We identified 11 cases of ENKTL from the departmental archives between January 2015 and June 2018. The clinicopathological and immunohistochemistry (IHC) findings of these tumors were analyzed. EBV encoded RNA (EBER) in situ hybridization (EBER-ISH) for EBV was done in eight cases. Results: The disease was more common in males (male: female ratio 1.8:1) with the mean age of 45 years (range 31-65 years). Sinonasal region was the most common site with 9 cases and skin and penis were involved in one case each. The patient with penile involvement on further investigations was found to have occult nasal involvement, Histomorphological features such as angiocentricity/angioinvasion was seen in seven cases (63.6%) and significant necrosis was present in all 11 cases (100%). All cases were uniformly positive for cytoplasmic CD3 and CD56 with high Ki67 proliferating index and EBER-ISH test for EBV was positive in all the eight cases. Conclusion: ENKTL is an aggressive NHL and should be differentiated from other T- and B-cell lymphomas as the prognosis and therapy differ. Nasal biopsies showing predominant necrosis and atypical lymphoid cells with angiocentricity must raise the suspicion of ENKTL and should be confirmed by immunomorphological and molecular studies.