Fig 1.
According to Adams [8], a basic granuloma need only contain organized mature macrophages in the context of chronic inflammation (left). Depending on the inciting stimulus, this arrangement may progress to include epithelioid transformation of these macrophages (middle), with formation of tightly joined interdigitated cell membranes. Several other features may subsequently appear in a complex granuloma (right), including central necrosis, multinucleated giant cells, and lymphocytes. Other “accessory” features not pictured include other leukocytes such as neutrophils or eosinophils, B and T cells, and fibrosis [10]. Image partially redrawn from [8].
Fig 2.
Pathological types of pulmonary cryptococcosis.
Panels A and B represent the extreme ends of a spectrum of pathological findings. This spectrum is represented differently in the 4 pathological types (C–F). (A) At one end of the spectrum, granulomatous inflammation featuring the pictured elements is capable of limiting cryptococcal growth. Dark gray frame color indicates location of these findings in subsequent panels. (B) At the other end of the spectrum is uncontrolled fungal growth with minimal or no inflammatory response. Light gray frame color indicates location of these findings in subsequent panels. (C) Peripheral pulmonary granuloma may consist entirely of granulomatous inflammation (dark gray only, left), or may have areas with emerging fungal growth (lighter gray adjacent to dark gray, right). (D) Granulomatous pneumonia, with patchy granulomatous response amid fungal growth entirely within alveoli. The patchiness of the overall picture (left) represents intra-alveolar pathology representing different parts of the spectrum. (E) Intracapillary/interstitial involvement, in which the alveoli are not involved. Patches of granulomatous inflammation are smaller and more dispersed, and pathology at varying points on the spectrum is seen only in the interstitial space. (F) Massive pulmonary involvement, with uncontrolled fungal growth in all areas.