Subcutaneous panniculitis-like T-cell lymphoma (SPTCL) is a rare T-cell lymphoma with a good prognosis. However, for unclear reasons, a minority of patients develop severe disease. A recent study has identified germline HAVCR2 (encoding TIM-3) mutations in familial cases of SPTCL, especially in Asian populations. The prevalence of this mutation in sporadic SPTCL is unknown. 
Data of 70 patients with sporadic SPTCL identified from the GFELC database between 2000 and 2019 have been reviewed regarding clinical presentation, HAVCR2 mutation status and clinical evolution after 35-month median follow-up. Median age was 42 years (1-90), 79% were women, 38% had an autoimmune disease history.
The most frequent presentation was multiple subcutaneous nodules of the limbs. 68% had associated B-symptoms. Hemophagocytic syndrome (HPS) was diagnosed in 12 patients (18%) including 5 severe forms.
Auto-antibodies were detected in 62% and antinuclear antibodies >1/80 in 58% of patients. A borderline histology with lupus panniculitis was found in 9 patients
Overall, PCR analysis detected a germline HAVCR2 mutation in 10/49 (20%) patients with suitable lesional material, from Cambodian, Vietnamese, New-Caledonian, Tahitian, Moroccan, Algerian and Indian Ocean origin (unknown in 2). HPS tended to be more frequent (4/10 versus 5/39, p=0.06) and was significantly more severe (3/10 versus 0, p=0.006) in patients with HAVCR2 mutation.
Most patients received first-line immunomodulatory treatment (76.5%).
Out of 67 patients with follow-up data, 49 (73%) were in complete response at last follow-up, 32% relapsed, 5 died, one of SPTCL 
Germline HAVCR2 mutations are rare in sporadic SPTCL but associated with severe HPS.

Long-term clinical outcome and HAVCR2 mutations in 70 patients with subcutaneous panniculitis-like T-cell lymphoma: a study from the French Cutaneous Lymphoma Group