[Characteristics of primary cutaneous rare nasal extranodal NK/T cell lymphoma: a clinicopathological study of 15 cases].

To investigate the clinicopathological features and differential diagnosis of primary cutaneous nasal extranodal NK/T cell lymphoma (pcENKTCL-NT). Fifteen cases of pcENKTCL-NT were collected at the First Affiliated Hospital of Zhengzhou University from January 2016 to December 2019. The clinical characteristics, morphological features, immunophenotypes, and results of in situ hybridization and gene detection were analyzed. Among the 15 patients, 7 were male and 8 were female, with a male to female ratio of 1.0∶1.1. Their ages ranged from 29 to 86 years, and the median age was 59.3 years. All patients were hospitalized for skin lesions, including skin ulcers, scattered patchy red papules, and local blisters. The skin lesion might be a hard nodular mass, and part of it was a confluent patchy erythema; it could be manifested as multiple scattered nodules of different sizes, and some lesions were like round ulceration. There were 8 cases of lower limbs, 4 cases of chest (1 case with upper limb lesions), 2 cases of trunk and 1 case of neck. Most of the patients were sensitive to GGDP regimen (cisplatin, dexamethasone, gemcitabine and pemostatin). Histologically, most lesions showed tumor cells invading the epidermis and skin appendages, dermal infiltration, diffuse distribution, vascular and peritubular destruction, and some subcutaneous adipose tissue involvement. Morphologically, most of the tumor cells were mixed with small-to medium-size lymphocytes, and some were large cells, mixed cells or small cells. Immunohistochemistry showed that CD3, CD3 ε and TIA-1 were expressed in all cases, but not CD20 and CD8. CD56 and granzyme B were expressed in most of the cases, and CD5 was not expressed. Ki-67 positive index was about 50%-90%. EBV in situ hybridization was positive in all cases. The clonal rearrangement of T cell receptor gene was found in some CD56 negative cases. The 15 patients were followed up for 5-45 months, and one of them was lost to follow-up. Five patients died within 5-13 months after the diagnosis, accounting for 35.7% (5/14) of the 14 patients. The average survival time of the deceased patients was 8.6 months. The incidence rate of pcENKTCL-NT is relatively low, but its biological behavior is aggressive and its prognosis is overall poor. Its skin lesions and histopathological features are relatively diverse. The diagnosis should be determined with using clinical data, histological morphology, immunophenotype and EB virus in situ hybridization. At the same time, attention should be paid to differential diagnosis from other cutaneous lymphoma with cytotoxic phenotype to avoid missed diagnosis and misdiagnosis.