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Central bronchi and pulmonary arteries are surrounded and enveloped by a strong connective-tissue sheath termed the peribronchovascular interstitium, extending from the level of the pulmonary hila into the peripheral lung. Thickening of the peribronchovascular interstitium can be seen in a wide variety of diseases. The CT appearance can be smooth, nodular, or irregular depending on the underlying cause. Many of the diseases affecting the peribronchovascular interstitium are entities that show a predilection for lymphatic routes, such as sarcoidosis, pulmonary lymphangitic carcinomatosis, silicosis, and lymphoproliferative disorders. There are other entities that mainly affect the peribronchovascular interstitium without a predominant perilymphatic distribution, such as hydrostatic pulmonary edema, cryptogenic organizing pneumonia, Kaposi's sarcoma, interstitial pulmonary emphysema, and interstitial hemorrhage. Although there is an overlap in radiologic features, some CT findings are useful in differentiating among these entities. When CT shows mainly peribronchovascular abnormality, the differential diagnosis is considerably reduced, and it is generally possible to reach the correct diagnosis by considering the clinical context. We illustrate the CT findings and pathologic correlation for a number of different disorders that mainly affect the peribronchovascular interstitium.

Thoracic aortic dissection is the most frequent cause of aortic emergency, and unless it is rapidly diagnosed and treated, the result is death. Helical computed tomography (CT) permits the diagnosis of acute aortic dissection with a sensitivity and specificity of nearly 100%. This imaging modality also enables differentiation between proximal aortic dissection (type A in the Stanford classification) and distal aortic dissection (Stanford type B), which are treated differently and have different prognoses. In 70% of patients in whom nontraumatic acute thoracic aortic dissection is diagnosed after evaluation with helical CT, scans show the typical signs of aortic dissection, with rupture and displacement of the intima. CT also can depict other pathologic entities with similar clinical manifestations, such as intramural hematoma and penetrating atherosclerotic ulcer. Awareness of the different radiologic appearances of these disease entities is essential for differential diagnosis. More than one-third of patients with aortic dissection show signs and symptoms indicative of systemic involvement. Because branch-vessel involvement may increase morbidity and mortality, in this group of patients it is important to evaluate the entire aorta so as to determine the distal extent of the dissection and detect any systemic involvement., (Copyright RSNA, 2003)

Stereotactic core needle biopsy (SCNB) allows specific histopathologic diagnoses to be made without surgery and has been demonstrated to be an accurate, cost-effective method of diagnosing breast disease, particularly nonpalpable lesions. However, recent studies have concluded that the diagnosis of atypical ductal hyperplasia (ADH) by means of SCNB has resulted in nearly equal odds that a coexisting malignant lesion will be missed. Furthermore, others have concluded that SCNB diagnosed as DCIS cannot reliably indicate the absence of tumor invasion in surgical excision. Between 1993 and 1998, 1,221 consecutive SCNB of mammographically identified lesions were performed using a 14-gauge automated device with an average of 5.3 cores obtained per lesion. ADH was identified in 19 (1.6%) lesions and DCIS in 89 (7.3%). Surgical biopsy was performed in 89 of these patients and histopathologic results from SCNB and surgical biopsies were reviewed and correlated. In 12 cases of ADH diagnosed by SCNB, surgical biopsy showed ADH in 8 (67%) cases and DCIS in the other 4 (33%) cases. In 77 cases of DCIS diagnosed by SCNB, a surgical biopsy showed DCIS in 55 (71%) cases, 6 more cases (8%) had DCIS with focal microinvasion, and 15 (19%) had invasive ductal carcinoma. In one case no residual tumor was found at surgery. In the author's patient population, the diagnosis of ADH at SCNB indicates high probability of DCIS or residual ADH in the surgical biopsy. The diagnosis of DCIS at SCNB is confirmed in the majority of surgical biopsies; however, a significant number of cases may show microinvasion or invasive carcinoma.

Pulmonary microvascular cytology consists of analysis of capillary blood sampled while a Swan-Ganz catheter is in the wedge position. This technique has proved to be useful in the diagnosis of lymphangitic spread of carcinoma in the lungs and there are case reports of their use in amniotic fluid embolism. Its usefulness in diagnosing fat embolism syndrome has been shown only rarely. We report a new case in which pulmonary microvascular cytologic study allowed a definite diagnosis of fat embolism syndrome. We suggest obtaining routinely samples of capillary blood when a pulmonary catheter is in place and fat embolism is suspected on a clinical basis.