Case 3 illustrates that even under optimal sampling conditions, the amount of “tumor” obtained may be minimal. A) The computed tomography scan shows a 10 × 8 cm anterior mediastinal mass which appeared to safely and reasonably be approached by either an incisional biopsy or fine-needle aspiration/core needle biopsy (FNA/CNB). The FNA/CNB sampled what appears to be an appropriate volume of the tumor. However, the tissue sections show that most of the sample was fibrosis; the areas composed of lymphocytes are outlined in yellow. The lymphocytes in these limited areas, amounting to 0.06 cm² in cross section, were correctly interpreted as non-neoplastic forms. With numerous small lymphocytes in the absence of any evidence of a neoplasm, an experienced pathologist interpreted these findings as a thymoma. On subsequent review, additional levels and studies were obtained specifically because the diagnosis of thymoma was based on the absence of neoplastic findings in an otherwise tiny specimen. Additional hematoxylin and eosin stain levels obtained from the original blocks showed rare, definitive Reed-Sternberg cells. B) Small samples are … sometimes tiny samples. And Reed-Sternberg cells are notoriously rare in Hodgkin lymphoma. Images show the most cellular piece of tissue at its largest is 2 mm. Within the red block are several variant forms of Reed-Sternberg cells, marked with a star in the high-power image.