Diagnostic pitfalls in cytological diagnosis of subcutaneous fungal infection in renal transplant recipients.

Renal transplant recipients (RTRs) are at increased risk of the development of a variety of skin infections that can result from graft-preserving immuno-suppressive therapy. In this study, we aimed to determine cytomorphological findings of fungal subcutaneous swelling in seven RTRs and to analyze diagnostic pitfalls in fungal cytology. A retrospective review of fine needle aspiration cytology (FNAC) smears of subcutaneous swelling with positive fungal elements in RTRs from 2008 to 2010 was performed. We had seven cases (all males; age range, 34-58 years, mean, 46.3 years). The time interval between the renal transplantation and appearance of swelling ranged from 8 to 19 months (mean, 13.4 months). The swelling was located on lower limb (six cases) and arm (one case). The lesion was solitary (six cases) and multiple (one case). The cytology of aspirated material showed branched septate fungal hyphae in six cases. These were well delineated on Periodic acid schiffs (PAS) and chromic silver methenamine (CSM) stains. One case showed presence of faint, thin walled, broad ribbon like hyphae. Culture of aspirated material was performed in four cases which grew phaeohyphomycosis in all. Histology of excised tissue showed numerous septate, branched, pigmented fungal elements suggestive of pheohyphomycosis in four cases and broad ribbon hyphae suggestive of zygomycosis in one case. All of our cases responded well with anti-fungal treatment. Fungal infection can manifest as subcutaneous swelling in RTRs. It is often severe, rapidly progressive and difficult to diagnose. FNAC is an important diagnostic tool which is simple, cost effective and rapid method.