Question: What would the diagnosis be if a lumbar puncture was performed and microscopy of CSF showed the following image?

Answer: This is cryptococcal meningitis. The specific stain used here is called India Ink.

Reference:

Robertson, Emma & Najjuka, Grace & Rolfes, Melissa & Akampurira, Andrew & Jain, Neena & Anantharanjit, Janani & Hohenburg, Maximilian & Tassieri, Manlio & Carlsson, Allan & Meya, David & Harrison, Thomas & Fries, Bettina & Boulware, David & Bicanic, Tihana. (2013). Cryptococcus neoformans Ex Vivo Capsule Size Is Associated With Intracranial Pressure and Host Immune Response in HIV-associated Cryptococcal Meningitis. The Journal of infectious diseases. 209. 10.1093/infdis/jit435.