Anaplastic large cell lymphoma with a small cell pattern is a rare T-cell lymphoma. This condition is more frequently seen in younger patients and should be considered when patients present with leucocytosis and constitutional symptoms. In this report, we describe our diagnostic work-up for one such case using blood, lymph node, and bone marrow aspirate samples, highlighting the variability of antigen expression seen in different sample types and methodologies. This case shows the importance of having a high index of suspicion and assessing CD30 and anaplastic lymphoma kinase expression in all suspected T-cell neoplasms even though this rare condition is not necessarily expected. 1. Introduction Anaplastic large cell lymphoma (ALCL) anaplastic lymphoma kinase positive (ALK+) is one of the subcategories of the mature T-cell neoplasms [1]. ALCL, ALK+ accounts for approximately 3% of cases of adult non-Hodgkin lymphomas and 10–20% of childhood lymphomas. There are many morphological variants of ALCL of which the small cell pattern variant accounts for 5–10% of cases. In this rare subtype, leukaemic manifestation is commonly seen in contrast to the other morphological variants [1–3]. Clonal T-cell populations may be demonstrated in the peripheral blood in a variety of clinical conditions. Although lymphocyte morphology may be indicative of a specific pathology, phenotyping of the population of interest is valuable in establishing the diagnosis. The apparent phenotype however may vary depending on technique, sample type, and cell population analysed. It is therefore essential to correlate phenotypic information with genetics and clinical presentation. 2. Case Presentation A 22-year-old female presented to her local hospital with a 16-day history of fevers, night sweats, nausea, and right upper quadrant abdominal pain. She also reported weight loss of nine and a half kilos. She had been referred several times to hospital and received several courses of intravenous antibiotics with no improvement. Full blood count analysis showed a leucocyte count of 14.2 × 109/L with mild lymphocytosis (5.4 × 109/L) and normal haemoglobin and platelet counts. A blood film showed a population of small, mature appearing lymphocytes with coarse nuclear chromatin and a second population of small lymphocytes with convoluted nuclei (Figure 1). Figure 1: Peripheral blood smear, modified Wrights stain (original magnification ×1000) showing atypical lymphocytes with convoluted nuclei. Biochemistry showed slightly elevated alanine transaminase (57？U/L (0–50？U/L)) and alkaline
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