Specimen Submission Guidelines for Pathologic Evaluation of Suspect Pneumonia Infections
Respiratory tract infections and pneumonias can be caused by a variety of bacteria, viruses, fungi and other microorganisms. Histopathologic changes in tissues and the distribution of microbial pathogens can vary significantly among different pneumonias. Microbial pathogens may be sparsely distributed in tissues and preferentially involve either large airways or pulmonary parenchyma or both. Because of these various factors, collection and submission of the appropriate tissues ensures the best chance of detecting the pathogen. Performance of specific immunohistochemical, molecular, or other assays will be determined using clinical and epidemiologic information provided by the submitter and the histopathologic features identified in the submitted tissue specimens.
Collection of Tissue Specimens
The preferred specimens would be a minimum of eight (8) blocks and fixed tissue representing different pulmonary sites listed below. In addition, specimens from other organs showing significant pathology should be submitted. Formalin-fixed paraffin embedded blocks made from BAL can also be submitted when available. Fresh-frozen tissue may be submitted for culture and molecular-based assays. The preferred pulmonary sites include:
- Hilar lung with segmental bronchi, primary bronchi, and trachea
- Peripheral pulmonary parenchyma from both lungs
- Specimens should be included from any other organ showing significant gross or microscopic pathology.
Submission of Specimens
Paraffin-embedded tissue blocks
In general, this is the preferred specimen and is especially important to submit in cases where tissues have been in formalin for a significant time. Prolonged fixation (>2 weeks) may interfere with some immunohistochemical and molecular diagnostic assays.
If available, we highly recommend that unprocessed tissues in 10% neutral buffered formalin be submitted in addition to paraffin blocks.
Although not optimal, if paraffin blocks are unavailable it may be possible to utilize unstained sections cut at 3–5 microns (10 slides per block) for immunohistochemistry and special stains but not molecular diagnostic assays (e.g. PCR).
Send separately on dry ice.
Electron Microscopy (EM) specimens
Samples fixed in glutaraldehyde and held in phosphate buffer. Sample containers are filled to the top with phosphate buffer and sent on wet ice. Do not freeze. Epoxy-embedded tissues are also accepted.