What organism is indicated by 'cup-shaped' cysts found in the lung biopsy of an immunocompromised patient?

The organism indicated by 'cup-shaped' cysts found in the lung biopsy of an immunocompromised patient is Pneumocystis jirovecci. This fungus is particularly significant in immunocompromised individuals, such as those with HIV/AIDS or those receiving immunosuppressive therapy, as it can cause a form of pneumonia known as Pneumocystis pneumonia (PCP).

Pneumocystis jirovecci cysts have a distinctive appearance that is often described as cup-shaped or disc-shaped under the microscope. These cysts are typically seen in lung tissue or bronchoalveolar lavage samples. The presence of these cysts in a lung biopsy helps to diagnose PCP, which is characterized by specific respiratory symptoms such as cough, difficulty breathing, and fever. The diagnosis is crucial as it informs the need for specific antifungal treatment and management for the patient.

Understanding the morphology of various pathogenic fungi helps in differentiating them in clinical settings. For instance, while Histoplasma capsulatum can also affect the lungs, it typically does not present with cup-shaped cysts but rather with microconidia and tuberculated macroconidia. Sporothrix schenckii is associated more with subcutaneous infections and presents differently,