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Radiographically, NHLs can appear as well-defined large, solitary or multiple nodular
opacities. Hilar adenopathy is not common, but a pleural effusion may be present along with
parenchymal involvement. Unilateral or bilateral moderate to large effusions can
occur.[604,607] Gallium scans may help to distinguish non-Hodgkin lymphomas from
infections and Kaposi's sarcoma.[547]
Microscopically, they are high-grade diffuse large cell (immunoblastic sarcoma) or
intermediate grade small noncleaved (Burkitt or Burkitt-like) lymphomas. Concomitant
infection with opportunistic agents may obscure lymphomatous infiltrates or be admixed with
them. Enlarged hilar lymph nodes may also be involved with malignant lymphoma.[641]

LYMPHOID INTERSTITIAL PNEUMONITIS.-- Lymphoid interstitial pneumonitis
(LIP) is associated with, but no longer considered a defining disease for AIDS in
childhood.[391,392] LIP is neither diagnostic of, nor frequently seen with, AIDS in the adult. It
must be differentiated from other infiltrative and interstitial pulmonary diseases. Tissue
diagnosis of LIP is usually made with an open lung biopsy, because bronchoscopic biopsies are
frequently nondiagnostic. Peripheral blood may show plasmacytosis and eosinophilia. A
presumptive clinical diagnosis of LIP for definition of AIDS requires that bilateral
reticulonodular interstitial pulmonary infiltrates must be present on chest roentgenogram for ≥2
months with no pathogen identified and no response to antibiotic treatment.[642]
Lymphoid interstitial pneumonitis may present with progressive dyspnea and dry cough,
along with systemic symptoms such as fever, night sweats, and weight loss. LIP cannot be
distinguished grossly. The radiographic pattern in children as seen on plain radiographs and with
computed tomography most often reveals a bilateral diffuse, symmetric, reticulonodular or
nodular pattern that is occasionally associated with hilar adenopathy.[608,643] The radiographic
appearance in adults, best seen with high-resolution CT imaging, can resemble Pneumocystis
jiroveci (carinii) pneumonia and include thickened bronchovascular bundles, variably sized
nodules in either centrilobular or subpleural locations, cysts ranging from 1 to 30 mm, and
bilateral ground glass opacities.[644]
The earliest microscopic pathologic finding is hyperplasia of bronchial associated
lymphoid tissue with aggregates of lymphocytes and plasma cells in a bronchovascular
distribution with minimal interstitial inflammation. In more advanced lesions, all lung fields
demonstrate a diffuse interstitial infiltrate of lymphocytes, plasma cells, and macrophages.
Additional features can include lymphoid aggregates with germinal centers, intraluminal fibrosis,
increased alveolar macrophages, and type II pneumonocyte hyperplasia. Advanced cases may
demonstrate confluent pulmonary nodules several centimeters in size. Rarely, poorly formed
granulomas may be present.[602,645]
Unlike chronic or nonspecific interstitial pneumonitis, LIP is more florid and extensive
and has a tendency to infiltrate alveolar septae. LIP, unlike malignant lymphomas, has a
predominance of small lymphocytes along with a mixture of inflammatory cell types.
Immunohistochemical staining of questionable infiltrates will demonstrate a polyclonal cellular
proliferation with LIP.[642] Lymphoid interstitial pneumonitis rarely results in progressive
pulmonary interstitial fibrosis.[602,645] Progression to lymphoma is possible but not common.
Many cases of LIP are accompanied by detectable Epstein-Barr virus (EBV) in lung tissue.[644]
There is a variable response to corticosteroid therapy. From a third to half of patients with LIP
die within 5 years of diagnosis and about 5% transform to lymphoma.[644]