Small‐cell predominant extranodal NK/T cell lymphoma, nasal type: clinicopathological analysis of a series of cases diagnosed in a Western population

Abstract

Aims Extranodal NK/T cell lymphoma, nasal type (ENKTCL) is usually composed of medium‐ to large‐sized lymphoid cells showing prominent angiotrophism and tumour cell necrosis. We report 13 cases composed predominantly of small lymphocytes diagnosed in the United States and Western Europe. Methods and results Patients included seven females and six males aged 17–75 years. Ten presented with sinonasal and three with buccal disease. Nine had stage IE/IIE and four had stage IV disease. In five of seven patients with multiple biopsies at different time‐intervals, the lymphoma was misinterpreted as representing chronic inflammation on an earlier biopsy. In all cases morphology showed a dense infiltrate of small lymphoid cells with minimal cytological atypia. Necrosis, angioinvasion and angiodestruction were each seen in 17%, 22% and 17% of biopsies. Median Ki67 was 5%. Four patients died of lymphoma 4–16 months after diagnosis, including three of four patients with stage IV disease; seven (54%) are alive with no evidence of disease at a median of 39 months; one patient with stage IV disease is alive at 10 months and one recurred at 17 months. Conclusions In sinonasal biopsies with predominantly small lymphocytic infiltrates with admixed chronic inflammation, focal hypercellularity, focal surface ulceration or microscopic bone invasion by small lymphoid cells should alert pathologists to the possibility of small‐cell predominant ENKTCL. Awareness of the full histological spectrum of ENKTCL, particularly in non‐endemic areas, is important in avoiding a delay in diagnosis and ensuring timely initiation of therapy.

Expression of programmed death‐1 in cutaneous extranodal natural killer/T‐cell lymphoma and its effect on clinical findings and biological behaviour

“…Cutaneous ENKTL cases that present erythematous to purpuric patches without a remarkable tumour or nodular lesion show a lower density of tumour cells than other clinical morphologies . These cases are mainly composed of small tumour cells and are less commonly associated with angiocentricity than other clinical morphologies …”

“…Cases of ENKTL consisting mostly of small cells have been described, but the diagnosis of such cases is challenging due to the lack of a visible mass and a subtle histology . Small‐cell‐predominant ENKTL shows a histology characterized by a low proliferation index, lack of angioinvasion and an associated reactive inflammatory background, including small reactive lymphocytes, histiocytes, eosinophils and often many plasma cells . Cutaneous ENKTL cases that present erythematous to purpuric patches without a remarkable tumour or nodular lesion show a lower density of tumour cells than other clinical morphologies .…”

“…Thus, our present study findings could not explain PD‐1 expression changes in association with the progression or disease stage of cutaneous ENKTL. Small‐tumour‐cell‐predominant ENKTL is associated with an inflammatory background including small reactive lymphocytes and the tumour presents clinically in patchy skin lesions . PD‐1‐positive TILs in these entities could control tumour growth, but not in medium‐ to large‐cell‐predominant entities, which have low expression of PD‐1, positive TILs and low inflammatory background.…”

Malignant effusions from extranodal NK/T‐cell lymphomas are frequently of anaplastic morphology with azurophilic granules and of T‐cell lineage

“…The angiocentric pattern of ENKTL is usually imperceptible on cytological specimens, while the necrotic background can be more easily observed in Papanicolaou‐stained smears. Cytologically, the neoplastic cells of ENKTL range from small or medium‐sized with irregular nuclei and coarse chromatin to large atypical lymphoid cells with pleomorphic and irregular‐shaped nuclei . A necrotic background consisting of both individual cell necrosis and amorphous necrotic materials has been described a hallmark finding of ENKTL in cytological materials .…”

CD30‐positive cutaneous extranodal natural killer/T‐cell lymphoma: clinicopathological features and survival outcomes

“…Our study demonstrated that CD30+ cutaneous ENKTL presents particular clinicopathological features. ENKTL is predominantly composed of medium‐ to large‐sized lymphoid cells, although cases with predominantly small cells histologically mimicking inflammatory conditions have been reported . CD30 positivity was associated with cellulitis‐like swelling or nodular lesions.…”