A 22-year-old woman has experienced increasing dyspnea for the past 2 months. On physical examination, she is afebrile and normotensive. Inspiratory wheezes are noted on auscultation of the chest. A chest CT scan shows an 8x10 cm posterior mediastinal mass that impinges on the trachea and esophagus. A mediastinoscopy is performed, and a biopsy of the mass microscopically shows scattered large multinucleated cells, with prominent nucleoli that mark with CD15, and lymphocytes and macrophages separated by dense collagenous bands. Which of the following cells is most likely to be seen microscopically in this biopsy specimen?

The lacunar cells and the CD15+ Reed-Sternberg cells indicate Hodgkin lymphoma, and the fibrous bands suggest the nodular sclerosis type. Lacunar cells have multilobed nuclei containing many small nucleoli. These cells have artifactual retraction of the cytoplasm around the nucleus, giving the cells their distinctive appearance. The nodular sclerosis type of Hodgkin lymphoma is more common in women. Atypical lymphocytes are characteristic in the peripheral blood of individuals with infectious mononucleosis. Hairy cell leukemia often is accompanied by splenomegaly, but not a mediastinal mass, and the leukemic cells are B cells. Histiocytes with Birbeck granules are characteristic of the Langerhans cell histiocytoses. Lymphoblasts that mark as T cells are seen in anterior mediastinal (thymic) masses in children with acute lymphoblastic leukemia/lymphoma. Myeloblasts are characteristic of acute myelogenous leukemia, which is occasionally accompanied by soft-tissue masses.