BI36 an Infiltrative Subcutaneous Mass Presenting As the First Sign of Relapse in a Patient with T Prolymphocytic Leukaemia

T prolymphocytic leukaemia (TPLL) is a rare form of post-thymic T-cell neoplasm, often involving the peripheral blood, bone marrow and spleen. Cutaneous involvement can be found in 25–35% of patients (Mallet RB, Matutes E, Catovsky D et al. Cutaneous infiltration in T-cell prolymphocytic leukaemia. Br J Dermatol 1995; 132: 263–6). Cutaneous features are not well recognized in dermatological literature and have been reported only in a limited number of case series (Herling M, Valbuena JR, Jones D, Medeiros LJ. Skin involvement in T-cell prolymphocytic leukemia. J Am Acad Dermatol 2007; 57: 533–4). There is a predilection towards the face and trunk, and reported morphologies include oedema, macules, papules, infiltrative erythema, nodules and erythroderma. A 76-year-old woman was admitted with a 6-week history of a nontender, indurated rash on her left upper arm, feeling generally unwell with vomiting and diarrhoea. Prior to admission, she was treated with flucloxacillin, doxycycline and co-amoxiclav with presumed cellulitis, but with no relief. On examination, a well-demarcated indurated plaque with central clearing and expanding erythema resembling erythema migrans was noted on her left upper arm. A symmetrical petechial rash and erythematous plaques on her legs were also present. The patient had been diagnosed with TPLL 18 months previously and had completed six cycles of alemtuzumab with disease remission. Blood investigations on this admission revealed a haemoglobin of 10.5 g dL−1, lymphocytosis of 11.20 × 109 L−1, acute kidney injury with creatinine 160 µmol L−1, elevated lactate dehydrogenase 546 IU L−1 and C-reactive protein 15 mg L−1. Her blood cultures were negative. Blood film revealed atypical lymphocytosis consistent with relapse of TPLL. Given the induration associated with the left-upper-arm lesion, an ultrasound and magnetic resonance imaging were performed, which revealed a 5 × 3 × 7-cm mass infiltrating her triceps brachialis. Core biopsy showed atypical lymphocytic infiltration in the dermis and grenz zone with positive CD3, CD4, CD5 and CD7, consistent with TPLL infiltration of the skin. Skin biopsy from her lower limb also showed cutaneous TPLL infiltration. Computed tomography of the thorax, abdomen and pelvis revealed diffuse lymphadenopathy and splenomegaly. Bendamustine was started for relapsed TPLL with significant reduction in the size of her left-upper-arm mass. This case highlights the various morphologies of cutaneous eruption that can present in a patient with TPLL. To our knowledge, this is the second case reported in the literature in a patient with TPLL presenting with a subcutaneous mass. Cutaneous features of TPLL may herald disease relapse with an ensuing aggressive clinical course. A high index of suspicion and low threshold for biopsy are needed, as extranodal involvement itself meets the criteria for active TPLL warranting treatment.