Comprehensive Cytopathologic, Flow Cytometric and Immunocytochemical Analysis of a Challenging Case of Small Cell...

Anaplastic large cell lymphoma (ALCL) is a high-grade non-Hodgkin lymphoma, accounting for approximately 3% of all non-Hodgkin lymphomas in adults and 15% of NHL in children. Around 70% of ALCLs show conventional morphology; however, several subtypes exist, such as the lympho-histiocytic, small cell, sarcomatous, giant cell-rich and signet-ring subtypes. The small cell variant of ALCL often presents as a diagnostic challenge due to its distinctive morphology, which differs significantly from the conventional ALCL.

A 9-year-old female presented with a history of chest and back pain for the last month. On examination, she had a gradually progressive anterior chest wall mass, which was fixed, globular and firm in consistency. Radiology revealed a mass measuring 4.9 × 3.3 × 4 cm with a lytic lesion involving the sternum along with generalised lymphadenopathy and bilateral kidney lesions. FNAC performed from the anterior chest mass demonstrated discretely scattered atypical lymphoid cells with eccentrically placed round to irregular nuclei, variably conspicuous nucleoli and scant cytoplasm. The background showed occasional lymphoglandular bodies. Immunocytochemistry on the cell block showed diffuse CD30 and ALK positivity. Flow cytometry revealed CD30-positive atypical lymphoid cells. Fluorescence in situ hybridization on the cytologic smears confirmed ALK gene rearrangement, thereby confirming a diagnosis of small cell variant of ALCL.

The index case report highlights the diagnostic complexities of the small cell variant of ALCL and emphasises the utility of various ancillary techniques like immunophenotyping and FISH, in conjunction with cytomorphology, in confirming such a challenging diagnosis.