The case of Dr Richard Carr which was posted in the spot diagnosis section of this wonderful website on Friday was really an amazing case of anaplastic large cell lymphoma (ALCL) rich in esinophils. The esinophils were so abundant that I missed the case as an infectious process !!!! This raised my attention to the possible disguised presentations of lymphomas.

Primary cutaneous T cell lymphoma can be disguised clinically as eczematous or inflammatory skin conditions for long time before a proper diagnosis is made. Some types of cutaneous lymphomas (eg. angiocenteric NK/T cell lymphoma) may also present as pyoderma gangrenosum like ulcers. Without proper examination of skin biopsies, the diagnosis can be delayed.

Pathologically, reactive infiltrates of esinophils and/or neutrophils can mask the malignant lymphoid population, especially in ALCL and in cutaneous Hodgkin's disease, and rapid examination of slides can lead to mistaken diagnosis of infectious processes (as what happened with me in Dr Carr's case!!). Negative cultures then should be a sign that necessitates re-consideration of the diagnosis.

It is the awareness of these possibilities that protect the dermatopathologists from missing such cases. Thanks to Dr Carr for sharing with us this interesting educational case. Knowing such pitfalls is vital in building our experience.