Introduction

Primary cutaneous gamma delta T-cell lymphomas (PCGDTCL) are rare, representing less than 1% of all cutaneous lymphomas. The aetiology is uncertain but involves chronic antigen stimulation and immunosuppression. PCGDTCL are a defined entity of the EORTC WHO classification of 2018 with various clinical presentations, most often manifesting as nodules or infiltrated plaques. The prognosis is generally poor and macrophage activation syndrome may occur. Treatment is mostly aggressive yet resistance to multiple chemotherapy or radiation therapy is common leading to frequent relapses. However, cases with an indolent evolution have been rarely reported in the literature since 2005, that have been successfully treated with systemic corticosteroids, methotrexate, bexarotene or phototherapy. We provide a retrospective series of five new indolent cases.

Observation

We report five cases of patients with heterogeneous clinical presentations diagnosed as PCGDTCL with indolent course: an 81-year-old man who presented with infiltrated plaques of the face, and four women aged 25, 30, 70 and 66, who presented respectively with localized subcutaneous nodular lesions of the lower limbs (case 2 and 5 ),urticarial lesions of the trunk (case 3) as well as nodular and necrotic lesions on the lower limbs (case 4). Despite a confirmed diagnosis of PCGDTCL, the clinical course was indolent and the patient achieved partial to complete response to treatment with bexarotene or methotrexate & systemic corticosteroids, with follow up ranging between 5 and 7 years. However, our 66-year-old patient (case 4) progressed with diffuse and aggressive disease after a 3-year follow-up.

Discussion

Our five cases highlight the importance of knowing the possibility of an indolent form of PCGDTCL, and the possibility to achieve a clinical remission with immunomodulatory treatments. This would prevent the unnecessary use of heavy treatments such as chemotherapy. A few case reports of equally indolent forms have already been described in the literature with various presentations of localized or diffuse lesions, as well as variable courses of progression. A few remained indolent while others became aggressive several years later. Conventional treatments such as phototherapy, radiotherapy or systemic corticosteroids proved to be efficient with most of such cases. However, some patients received multiple lines of treatment including polychemotherapy achieving partial to complete responses. They remain in remission several years post-treatment until 15 years of follow-up. Nevertheless, it is prudent to maintain close surveillance to early detect any secondarily aggressive development as noted in our 4th case of our series.