47 from the areas of the more heavily exposed groups. Three other subjects from this island with the same exposure have had surgical excision of nodules which proved to be benign adenomas. A fifth lesion that was papillary (the size of a match head) was foundin a subject from anisland wherethe exposure was intermediate (Ailingnae); several other individuals exposed there havedeveloped benignlesions after a latent period somewhat longer than for those exposed on Rongelap. After review of this papillary lesion by eleven pathologists,* opinion is divided as to whether it should be considered malignant (Figure 344); we have recordedit in ourstatistics as benign in view of the majority opinion. A few lesions of the thyroid fall into an uncer- tain category in which even the most experienced *Drs. S. Warren, W. Meissner, and M.A. Legg, New England Deaconess Hospital; J.D. Reid, Cleveland Metropolitan General Hospital; T. Winship (deceased); L.B. Woolner, Mayo Clinic; L.V. Ackerman, SUNYat Stony Brook; R.V. Rosvoll, Emory University; and S. Robbins, A. Vickery, and B. Castle- man, Massachusetts General Hospital. pathologists are unable to reach a firm opinion as to a diagnosis of malignancy. Someofthese lesions ultimately proved to have been malignantas evi- denced by a distant metastasis someyears afterremoval of the primarylesion. It seems that a neoplasm must reach somesignificantsize beforeit can unequivocallysatisfy the criteria for a diagnosis of malignancy even though smaller lesions may have cellular characteristics that suggest malignant capabilities. In clinical practice many lesions are of sufficient size that the criteria for malignancyare readily fulfilled. Among the Marshallese patients most of the thyroid nodules either were detected by palpation when scarcely | cm in diameter or were foundcoincidentally to removal of palpable adenoma. Manylesions showing atypical cellularity were so small that perhaps they had not yet had an opportunity to manifest all the usual criteria upon which a diagnosis of malignancy may be based. Figures 33C and 34A show one such minute lesion. This emphasizes the importanceof the early diagnosis and treatmentof Marshallese lesions. ‘e sor ey. 3 Cey SUE ahOF. tS espeSanat fe Seg ESESereuaeeeWeentees, oS y ; | Figure 34, Examples of very minute neoplasms, only a few mm in diameter and completely en- capsulated but composedof cells whose pattern suggests that if the lesions were larger they might display features prompting a suspicion of malignancy. In both examples shown (4, x 162, sub- ject No. 8, 1972; B, x 91, No. 36, 1969) evidence of biood vessel or lymphatic invasionis lacking, and the capsule, which was very thin, was not breeched. The entire lesion of A is shown in Figure 33C, whereits size can be compared with that of surrounding normalfollicles. Both these examples are from thyroids that had no frankly malignantlesions elsewhere in them. os ‘