EXERCISE 4-8. MULTIPLE PULMONARY NODULES
4-13. The most likely cause of the multiple pulmonary nodules in Case 4-13 (Figure 4-40) is metastasis. herpes simplex pneumonia.
4-13. In this case, the chest radiograph shows multiple, smoothly marginated, solid nodules in both lungs. These nodules are distributed diffusely and have vari-ous diameters (A is the correct answer to Question 4-13). The heart is normal in size and shape.
The radiographic pattern of multiple pulmonary nodules is frequently encountered (Table 4-8). The clinical setting has considerable influence on the differential diagnosis in such cases and should always be taken into account when assess-ing patients with this pattern. However, the differential diag-nosis may be narrowed by assessing the absolute size of the nodules, the uniformity of their size, their marginal charac-teristics, whether or not they are calcified, and whether or not they are cavitary. In adults the most common causes of multiple nodules are metastatic neoplasm and infectious disease. Metastatic neoplasm may result from carcinoma, sarcoma, or lymphoma. Pulmonary metastases may be of any size and number. In contrast to inflammatory nodules, nodular pulmonary metastases are often of various diame-ters. Metastases are usually of soft-tissue density similar to muscle or blood (Figure 4-41). Metastases may rarely be cal-cified if the patient has a sarcoma that makes bone or carti-lage (eg, osteosarcoma). Differentiation is most commonly made by the clinical setting or review of old studies, but de-termination of the correct diagnosis may require tissue biopsy for confirmation.
Multiple pulmonary nodules may also be due to infec-tious disease, most commonly fungal or mycobacterial infec-tions. In the United States, the most common fungus is histoplasmosis (Figure 4-42), although there are regional variations. Calcified nodules that are all of similar size sug-gest a previous infection with either histoplasmosis or tuber-culosis. Nodules seen in acute infection are often not as sharply defined as metastases. This is especially true if the nodules represent acinar shadows. In these instances, the nodule is approximately 5 to 10 mm in diameter and is ill de-fined or fuzzy on its margin. Acinar nodules develop in pa-tients with viral pneumonias such as herpes pneumonia or chicken pox (varicella) pneumonia.
Multiple pulmonary nodules may also develop in a wide variety of other disorders, including Wegener’s granulomato-sis and arteriovenous malformations, but would not be as numerous as in this case.
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