Cryptococcal dumbbell inflammatory pseudotumor mimicking skull histiocytic sarcoma in immunocompetent patient

Cryptococcus neoformans is an opportunistic fungus with marked neurotropism, classically affecting immunocompromised patients, even though occasionally reported in immunocompetent hosts. Skull involvement is exceptionally rare and may radiologically mimic malignant tumors, causing diagnostic delays.

A 34-year-old immunocompetent male presented with a painless, progressive left parieto-occipital scalp swelling over 3 weeks. Imaging revealed a well-defined, dumbbell-shaped cystic mass beneath the scalp, causing lytic skull erosion and limited intracranial extension, suggestive of atypical meningioma or skull-based sarcoma. Surgical excision was performed, showing dural infiltration without leptomeningeal spread. Histopathology, the mass revealed granulomatous inflammation with abundant CD68+ histiocytes, mixed B- and T-cell infiltrates, and encapsulated budding yeasts (5-10 μm) within enlarged perivascular spaces. Gomori Methenamine Silver and periodic acid-Schiff staining confirmed fungal elements; culture identified Cryptococcus species.

Skull cryptococcosis in immunocompetent patients is rare but can occasionally present as an inflammatory pseudotumor with osteomyelitis and extracranial extension. Its imaging resemblance to aggressive neoplasms underscores the importance of including fungal etiologies in the differential diagnosis of destructive skull lesions, regardless of the immune status.