Page 254 - AIDSBK23C

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CYTOPATHOLOGY IN AIDS

Diagnostic procedures yielding primarily cytopathologic specimens, rather than tissue
biopsies, in the respiratory tract include bronchial brushings, bronchoalveolar lavage, and sputum
collection. Collection of these specimens is mainly for diagnosis of P jiroveci (carinii). Without
special stains, the appearance of small eosinophilic foamy bodies is quite suggestive of
Pneumocystis.[411] The diagnostic sensitivity in specimens obtained from bronchial washing or
induced sputum may be aided by use of an indirect fluorescent antibody test for P jiroveci
(carinii).[1035]
Bronchoalveolar lavage (BAL) remains overall the most useful procedure for obtaining
diagnostic material from lung in immunocompromised patients, with a diagnostic yield of over
50%.[659] BAL is the method of choice for diagnosis of Pneumocystis jiroveci (carinii)
pneumonia, with a yield of 90% (95% for sampling of multiple sites).[409,660] In BAL fluids,
diagnosis of cytomegalovirus (CMV) is aided by immunohistochemical staining and/or in situ
hybridization techniques, which are more sensitive than CMV detection by morphology
alone.[1036]
Budding yeasts of Candida are often seen in sputum specimens, in specimens obtained at
bronchoscopy, or in esophageal brushings. Yeast organisms in such specimens may represent
oral contamination rather than a pathologic process. Cytomegalovirus and Aspergillus likewise
uncommonly represent pathogens in BAL specimens. Other infectious agents are seen much less
frequently. Diagnosis of malignant lymphomas or KS from pulmonary cytologic material is
extremely difficult.
Stereotaxic brain biopsy is most often undertaken to diagnose mass lesions that represent
possible T gondii infection or malignant lymphoma.[739] Diagnosis of other neurologic
conditions in AIDS is hampered by poor yield from sampling error resulting from the focal
nature of most processes in brain. However, cytology of tissues obtained from the brain by
stereotactic biopsy for intraoperative diagnosis may be more sensitive for diagnosis than frozen
sections, though the presence of necrosis and gliosis can make diagnosis difficult.[740]
Fine needle aspiration (FNA) cytology may be performed to diagnose mass lesions found
on roentgenography. The most frequently sampled sites include lymph nodes, salivary gland,
liver, paraspinal area, extremity, and chest wall. A specific diagnosis can be made in half of
cases. Enlarged lymph nodes are prime targets for such procedures. Progressive generalized
lymphadenopathy is a common diagnosis rendered by FNA of lymph node. Diagnosis of
neoplasms such as KS and non-Hodgkin lymphoma are challenging by FNA, but can be aided by
immunohistochemical staining. Malignant lymphomas can sometimes be diagnosed by the
appearance of a monomorphous population of large atypical lymphoid cells. Aspirates with
inflammatory cells, particularly macrophages, should be screened with special stains to detect
fungal or mycobacterial organisms. The yield for diagnosis of M tuberculosis with FNA is
47%.[1037]
Imprints or smears of tissue specimens removed at surgery may aid in diagnosis of
mycobacterial infections by providing more detail than paraffin sections.[448]