Herlant’s Tetrachrome Staining, a Useful Tool for Pituitary Adenoma Diagnosis

Introduction: The morphologic diagnosis of pituitary adenomas (PA) is based on immunohistochemistry (IHC). In Romania, IHC diagnosis of PA is restricted, all of the specific antibodies being very expensive. A histochemical staining, Herlant’s tetrachrome (HTCS), was described several years ago, but it was not widely used for diagnostic purposes because of technical difficulties. The aim of this paper is to bring into discussion this staining, to highlight its benefits, to improve the technical procedures and to establish a protocol, which combining both HTCS and IHC, facilitates the diagnosis of PA and, especially, substantially reduces the costs.
Methods: HTCS was performed using normal pituitary glands. The optimal time of staining and the optimal concentration of different solutions were established for each step of the staining.
Results: The improved technical procedure of HTCS is described. The staining features of all cellular types of the pituitary gland are depicted and illustrated: the chromophore cells, GH-secreting cells stained in orange, PRL-secreting cells in red-violet and ACTH-cells in dark blue, while cromophobe cells stained light blue. These staining features can be extrapolated to the diagnosis of PAs, as they consist of a proliferation of such cells.
Conclusion: HTCS’s benefit is in functional PAs: it can identify GH, PRL, ACTH and TSH-adenomas, according to the cell type staining. A two-step diagnostic protocol is proposed, allowing the use of two, maximum three antibodies, instead of six: first step HTCS, and second step IHC.