Approach to the Diagnosis of Nonneoplastic Parenchymal Lung Nodules



Approach to the Diagnosis of Nonneoplastic Parenchymal Lung Nodules


Allen P. Burke, M.D.

Marie-Christine Aubry, M.D.

Haresh Mani, M.D.



Poorly Formed Granulomas

Granulomas in the lung parenchyma are generally classified as poorly or well formed. Poorly formed granulomas are a hallmark of hypersensitivity to inhaled allergens. They are indistinct collections of lymphocytes with macrophages, typically giant cells. Poorly formed granulomas are generally near the bronchovascular bundles and are often associated with interstitial inflammation (Fig. 9.1).







FIGURE 9.1 ▲ Poorly formed granuloma. The interstitium contains chronic inflammation with granulomatous inflammation in the center (epithelioid macrophages with a few giant cells).


Well-Formed Granulomas

Well-formed granulomas are found in sarcoid or infections, usually fungal or mycobacterial. sarcoid and infections (Table 9.1). There is a compact collection of epithelioid histiocytes with a discrete border (Fig. 9.2) and a subpopulation of T lymphocytes. Sarcoid granulomas are found in a lymphatic distribution in the bronchovascular bundles, interlobular septa, and subpleural space. Fibrosis is a characteristic of sarcoid granulomas (Fig. 9.3). Infectious granulomas are, in contrast, asymmetric and occur randomly in the parenchyma. Further, presence of significant lymphoplasmacytic inflammation favors an infectious etiology. Well-formed granulomas of any cause, but especially sarcoid, may contain mineral deposits (Schaumann bodies), which should not
be mistaken for pneumoconiosis (Fig. 9.3). Asteroid bodies are also nonspecific features of well-formed granulomas (Fig. 9.4).








TABLE 9.1 Histologic Features of Pulmonary Granulomas



















































































































Diagnosis

Necrosis

Multiplicity

Contour

Lymphatic Distribution

Neutrophils

Multinucleated Macrophages

Necrotizing Vasculitis

Distinguishing Features


Sarcoidosis

10%-20%a

100%

Regular (100%)

70%-100%

Absent

100%

Absent

Diffuse, symmetric


Mycobacterial infectionb

75%

90%

Regular (2/3)

20%

80%

100%

Absent

Positive AFB stain (about 50%)


Histoplasmosis

>90%

75%

Regular (80%)

<5%

50%

80%-90%

Absent

Positive GMS stain (>90%, but requires careful review)


Coccidioidomycosis

>90%

80%

Regular (90%)

<5%

90% also, frequent eosinophils

90%

Absent

Positive GMS stain (>90%)


Blastomycosis

>90%

80%

Irregular (75%)

<5%

100%

50%-80%

Absent

Positive GMS stain (>90%)


Talc granulomas

Absent

100%

Regular

Absent

Infrequent

100%

Absent

Birefringent crystals


Granulomatosis with polyangiitis

100%

>90%

Irregular (100%)

0

100% (usually with apoptosis)

60%

20%-50%

Apoptotic neutrophils causing basophilic necrosis


Idiopathic (unexplained)

>95%; abundant in 75%c

80%

Regular (60%)

<20%

50%

80%

Absent

Are presumed infections; some will demonstrate NTM DNA by PCR


Rheumatoid nodule

100%

60%

Irregular (60%)

0

80%

100%

Absent

History and serology


Hyalinizing granuloma

Absent

50%

Regular

Absent

Absent

Absent

Absent

IgG4-related histologic features


Percentages are approximate. For further histologic features distinguishing fungal infections, see Chapter 41 and 44.


a Necrosis in sarcoid is usually inconspicuous and central in the granuloma.


b Nontuberculous (atypical) mycobacterial granulomas are more frequently encountered as lung nodules than tuberculosis. Histologic features are different in infections in immunocompromised patients, and discrete nodules are not as common (see Chapter 40).


c Idiopathic nonnecrotizing granulomatous disease is synonymous with sarcoidosis and is typically bilateral and symmetric. Solitary idiopathic necrotizing granulomas are common. Well-formed granulomas that do not have necrosis and that form solitary lung nodules are rare.


NTM, nontuberculous mycobacteria; PCR, polymerase chain reaction.


Adapted in part from Mukhopadhyay S, Wilcox BE, Myers JL, et al. Pulmonary necrotizing granulomas of unknown cause: clinical and pathologic analysis of 131 patients with completely resected nodules. Chest. 2013;144:813-824.

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Aug 19, 2016 | Posted by in CARDIOLOGY | Comments Off on Approach to the Diagnosis of Nonneoplastic Parenchymal Lung Nodules

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