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We evaluated the presence of anterior pituitary hormones; follicle-stimulating hormone (FSH) and its beta-subunit (beta-FSH), luteinizing hormone (LH) and its beta-subunit (beta-LH), beta-subunit of thyroid-stimulating hormone (beta-TSH), adrenocorticotropic hormone (ACTH), growth hormone (GH), and prolactin (PRL); the placental hormone human chorionic gonadotropin (hCG); and somatostatin, in paraffin and frozen sections of the human thymus. Epithelial cells in the medulla were immunoreactive for most of these hormones, in varying density and intensity of labeling. The cells labeled varied from epithelial cells surrounding Hassall's corpuscles toward solitary cells or small epithelial aggregates in the medulla. FSH immunoreactivity did occur predominantly in epithelial cells of the cortex, in apparent contrast to the predominant medullary location of cells immunolabeled for beta-FSH. The epithelial nature of FSH-immunoreactive cells was confirmed by two-color immunohistochemistry with anti-keratin antibody. In addition to FSH, some epithelial cells in subcapsule and cortex were labeled by antibodies to beta-FSH, beta-LH, beta-TSH, ACTH, GH, and PRL. Some macrophage-like cells surrounded by a rosette of lymphocytes were immunoreactive for FSH and GH. Some interdigitating reticulum-like cells were labeled by anti-beta-LH. Immunolabeling of lymphocytes was found for hCG, especially lymphocytes in the medulla. Two-color immunohistochemistry with anti-CD3 revealed a strong CD3 expression on hCG-immunoreactive cells, whereas CD3-negative cells were hCG-negative. T cells immunolabeled for hCG were also found in peripheral lymphoid organs.

We report the case of a solitary ulcerating lesion on the elbow of a 32-year-old man. Routine histopathological examination strongly suggested a histiocytic malignancy. However, electron-microscopical, enzyme-cytochemical, and immunological studies revealed that the "tumor" cells were T lymphocytes with an unusual (Leu 1+, Leu 3a+, Leu 4+, Leu 5b+, OKT4+, HLA-DR+, Ki-1+, Leu MI+) immunological phenotype and an even more uncommon morphology characterized by the development of giant multivesicular bodies giving some cells a signet-ring cell appearance, and autophagocytosis. The lesion healed spontaneously, notwithstanding its malignant histology.