Histiocytic lymphoma presenting as a testicular tumour and terminating in acute monoblastic leukaemia

A 58 year old man presented in 1995 with a swollen testicle. After orchidec tomy. a diagnosis of poorly differentiated lymphoma was made. Lymphoid, epi thelial, and seminoma markers were all negative. Six months later he develo ped a buccal lesion, which was biopsied and reported as a high grade non-Ho dgkin's lymphoma. It responded completely to chemotherapy but within a year he developed a forearm swelling, which was biopsied and imprints made befo re fixation of the material. Immunocytochemistry on the imprints showed pos itivity with antibodies to CD4, CD68, and muramidase, and the non-specific esterase cytochemical stain was strongly positive, leading to a diagnosis o f hue histiocytic lymphoma. Despite further treatment, the patient entered a terminal acute leukaemic phase, the blasts marking as monoblasts. Review of all the biopsies, including molecular investigations and further immunoh istochemistry studies performed retrospectively on the original biopsy, dem onstrated that this was the same malignant cell Line throughout, and we con clude that this is a case of histiocytic lymphoma, initially presenting as a testicular tumour and terminating in acute monoblastic leukaemia. it diag nosis of histiocytic lymphoma should be considered when lymphoid markers ar e negative in an apparent lymphoma, but should not be made without recourse to appropriate immunophenotypic and molecular studies.