Histoplasmosis: cytodiagnosis and review of literature with special emphasis on differential diagnosis on cytomorphology.

BACKGROUND: Human infection with Histoplasma capsulatum runs the gamut from asymptomatic to disseminated disease. In immunocompromised patients, a tiny inoculum can lead to widespread disseminated infection. Early diagnosis and initiation of treatment is therefore important.
OBJECTIVE: To review the cases of histoplasmosis diagnosed on fine needle aspiration cytology (FNAC) and to discuss the clinical presentation, associated inflammatory response, load of organisms and differential diagnosis on cytomorphology in these cases.
METHODS: Retrospective review of seven cases of histoplasmosis at a tertiary-care centre during the period from 1998 to 2009 was performed. Clinical presentation along with cytomorphological features were studied and discussed in detail.
RESULTS: The mean age of patients was 48.6 years and six out of seven were male. History of immunodeficiency (HIV) was available in five cases. Six patients presented with peripheral and/or abdominal lymphadenopathy. One patient had nodular shadows in both lungs and two also had skin lesions. On cytological smears, a variable load of uniform round to oval, about 2-4 microm in diameter, budding yeasts were seen intracellularly (within histiocytes) as well as extracellularly. In one case (HIV positive), these organisms were also seen within neutrophil polymorphonuclear leucocytes. In two cases, an inflammatory response in the form of epithelioid cell granulomas along with multinucleated giant cells was seen.
CONCLUSIONS: FNAC is a reliable tool to recognize infection with H. capsulatum in tissues. This infection can cause a variable inflammatory response, which should be considered while reporting on such cases.