Retrosternal Infiltration in Malignant Lymphoma

It is generally agreed that there are no uniformly pathognomonic roentgenologic signs of intrathoracic lymphomas, and that many different types of change may be encountered (9). Previously, investigators (5, 9) have classified the changes generally encountered into six groups: (1) mediastinal tumor; (2) hilar lymphonodular masses; (3) diffuse infiltration of lung parenchyma; (4) isolated nodules in the parenchyma; (5) pleural infiltration; (6) pleural effusion. In our cases of the intrathoracic lymphoma group, we have occasionally observed a retrosternal infiltration, occurring alone or in conjunction with one or several of the usually noted localizations of lymphoma, but not previously described as such. It has been found with and without associated sternal involvement and pre-sternal edema, and in all types of cases classified under the broad heading of malignant lymphoma. Pathology Lymphoid tissue involvement is the common denominator of the lymphoma group and, as Wolpaw et al. (10) have stated, “…the character of the disease in any organ or region of the body will therefore be determined by the location of its lymphoid tissue and the degree to which it is affected by the etiologic factor.” The retrosternal lymphoid tissue distribution is primarily represented by the bilateral, symmetrically arranged internal mammary chain of nodes, receiving afferent tributaries from the anterior parietal pleura and subpleural network on the pulmonary side, from the pericardium, and from the medial part of the chest wall via the intercostal lymph vessels. The bronchomediastinal trunks may also terminate by uniting with the internal mammary chains (Fig. 1) (8). It thus becomes evident that retrosternal involvement may be readily correlated with the anatomical distribution of lymphoid tissue within this region of the chest, arising as a frequent and often early extension from previously affected intrathoracic structures or by invasion from metastatic bone marrow foci in sternum and ribs, and possibly, also, as a primary focus. Dresser and Spencer (4) and others (2, 3, 10) have noted that the sternum and ribs are favorite sites for bone involvement by lymphoma. From the facts presented above, it would seem likely that retrosternal infiltration might be encountered as a preliminary stage before actual bone infiltration, or as part of the soft-tissue reaction secondary to a preceding bone lesion. Several cases have been reported in which massive pulmonary involvement caused tough adhesions of granulomatous tissue to bind portions of the lung solidly against the chest wall, and in some of these cases the process extended transpleurally into the contiguous ribs (9). Bone involvement in malignant lymphoma has been known for a long time, with the sternum, ribs, vertebral spine, and pelvis being most frequently affected. In one series showing bone changes, the lesions appeared early in the course of the disease in nearly 25 per cent of the cases (4).