Immunohistochemical analyses of oncocytic and chromophobe pituitary adenomas

Oncocytic Transformation in Pituitary Adenomas: Immunohistochemical Analyses of 65 Cases

Context.—Oncocytic change in pituitary adenomas has been evaluated by electron microscopy and more recently by immunohistochemistry. The clinical significance of this change is not well known, although some reports suggest a relationship with more aggressive behavior.

Objective.—To assess the frequency of oncocytic change in pituitary adenomas and to correlate this finding with clinicopathologic factors.

Design.—We studied oncocytic change in a series of 65 pituitary adenomas by immunohistochemistry. According to the percentage of oncocytic cells stained by antimitochondrial antibody, adenomas were classified in 3 groups: 50% or more, 10% to 49%, and 1% to 9% of oncocytic cells.

Results.—Eight cases (12.3%) showing at least 50% of oncocytic cells were classified as oncocytic adenomas: 6 were gonadotroph adenomas and 2 were null-cell adenomas. Among the remaining cases, 9 (14%; all gonadotroph adenomas) showed 10% to 49% oncocytic cells, and in 14 cases (21.5%; 5 gonadotroph adenomas, 6 somatotroph adenomas, 2 corticotroph adenomas, and 1 thyrotroph adenoma) between 1% and 9% were shown. Patients with adenomas that showed oncocytic change presented more frequently at a higher average age (P = .05), but no relationship with extrasellar extension or proliferative activity measured by Ki-67 was observed. In somatotroph adenomas, cases with oncocytic change showed higher percentages of Ki-67 (P = .05) but no correlation with extrasellar extension or cytokeratin staining (dot pattern versus perinuclear) was found.

Conclusion.—Adenomas with oncocytic change present more frequently in older patients, but they are not clinically more aggressive. In addition, somatotroph adenomas with oncocytic cells show similar cytokeratin pattern and higher proliferative activity, which is not correlated with local aggressiveness.

Pituitary oncocytomas: clinical features, characteristics in cell culture, and treatment recommendations

To determine whether there are significant differences between oncocytomas and pituitary adenomas, we evaluated clinical features, treatment regimens and outcome in 23 males and 9 females (average age 64 years, range 43-81 years) with the histologic diagnosis of pure pituitary oncocytomas (> 95% oncocytes). Symptom duration was six to twelve months in 6 cases (19%) and more than one year in 19 cases (59%). Three patients presented with sudden onset of symptoms, and were found to have hemorrhage within their tumors. Visual loss (69%) and symptoms of hypopituitarism (44%) were the most common presenting complaints. Preoperative endocrine profiles revealed abnormalities in most cases, including pituitary insufficiency in 56% and hyperprolactinemia in 59%. The tumors were typically large at presentation; all but one had suprasellar extension. 28 patients underwent transsphenoidal tumor resections; 4 underwent subfrontal craniotomies. Gross dural invasion was found at surgery in 11 cases. At a mean followup of 31 months (range 2-68 months), recurrent tumor was identified in 4 patients (12.5%). Tumor size, dural invasion, preoperative endocrine profile, and postoperative radiotherapy did not correlate with recurrence. Among seven oncocytomas grown in culture, five demonstrated two distinct cell types consisting of oncocytes and typical adenoma cells, respectively. Oncocytomas often have a different clinical presentation than functional pituitary adenomas.

Contribution of immunohistochemistry, electron microscopy, and cell culture to the characterization of nonfunctioning pituitary adenomas: a study of 40 cases

We studied 40 endocrinologically inactive pituitary adenomas by immunohistochemistry, electron microscopy, and cell culture in order to determine the incidence of gonadotropic adenomas and to classify nonfunctioning adenomas. Immunohistochemical studies using a large panel of monoclonal and polyclonal antibodies identified the following nonfunctioning adenomas: 20 gonadotropic adenomas, four silent corticotropic adenomas, one plurihormonal adenoma, and 15 nonsecreting adenomas. Among nonsecreting adenomas, ultrastructural study of 13 cases identified seven null cell adenomas and six oncocytomas. Silent corticotropic adenomas were classified into subtypes I, II, and III according to Kovacs and Horvath. Most often, gonadotropic adenomas displayed a varying number of oncocytic cells, characteristic secretory granules, and a prominent Golgi apparatus. Postembedding immunoelectron microscopy was performed on eight gonadotropic or nonsecreting adenomas, but this technique did not provide any additional information. Six gonadotropic adenomas and 10 so-called nonsecreting adenomas were studied in primary cell cultures. The six gonadotropic adenomas and seven of the 10 nonsecreting adenomas released gonadotropins in the culture medium. The use of in vitro results as a supplementary diagnostic criterion allowed classification of the 40 nonfunctioning adenomas as follows: 27 gonadotropic adenomas, four silent corticotropic adenomas, one plurihormonal adenoma, and eight nonsecreting adenomas. These results demonstrate a high proportion of gonadotropic adenomas among nonfunctioning adenomas (67.5%) and the usefulness of several techniques in characterizing this type of pituitary adenoma.