Pseudocyst of tumor involution: a sign of nodal control in radiation therapy of head and neck carcinoma.

Regression of large metastatic lymph nodes in head and neck carcinoma following successful radiation therapy is a relatively lengthy process. This is especially true for nodes containing central necrosis. This article on serial CT scans identifies morphologic changes of prognostic significance, demonstrated on the basis of two case reports. Specifically identified are the transitional morphologic state, which is radiographically indistinguishable from an inflammatory condition, and, in addition, a seemingly end-stage of nodal tumor involution, which is represented by a pseudocyst formation, in a patient of long-standing duration.