A 59 YEAR‐OLD MAN WITH SELLAR LESION

CLINICAL HISTORY AND IMAGING STUDIES

A 59 year‐old man with no significant past medical history presented to our neurosurgery clinic with progressive vision loss. Magnetic resonance imaging of his brain revealed a 3.3 cm × 3.3 cm × 3.4 cm suprasellar mass (Figure A). Endocrine evaluation revealed increased FSH levels. The patient was treated initially with high‐dose methylprednisolone with subsequent resolution of his left‐sided visual disturbances. On admission day four, he underwent subtotal transcranial resection of the suprasellar mass. Post‐operatively the patient's course was complicated by transient diabetes insipidus treated with several doses of desmopressin. After surgery, therapy was initiated with levothyroxine, hydrocortisone, and testosterone; he was discharged 17 days after his resection.

Figure A–F.

NEUROPATHOLOGICAL FINDINGS

The majority of the tumor showed a pituitary adenoma. These were found to exhibit immunoreactivity for synaptophysin, FSH, and luteinizing hormone (LH) as well as focal reactivity for thyroid stimulating hormone (TSH). The tumor cells were negative for adrenocorticotropic hormone (ACTH), growth hormone (GH), and prolactin. MIB‐1 staining for the proliferative marker Ki‐67 labeled less than 2% of cells.

Scattered throughout the adenoma were small nests of epithelial cells with squamoid differentiation that showed peripheral palisading of the nuclei and focal stellate reticular appearance (Figure B and C). These nests were immunoreactive for high molecular weight cytokeratin (HMWK, Figure D) and p63 (Figure E). Some of the basal cells within these nests showed proliferative activity as assessed by labeling with the MIB‐1 antibody (Figure F).

DIAGNOSIS

Pituitary gonadotroph adenoma with adamantinomatous craniopharyngioma

DISCUSSION

Nests of squamous cell epithelium have long been recognized to exist within the normal pituitary gland and are thought to represent remnants of the embryologic hypophyseal‐pharyngeal duct. Luse and Kernohan investigated 1364 pituitary glands and found that 333 (24 percent) had nests of squamous epithelium (5). Of these 333 pituitary glands, only one had squamous nests outside of the pars tuberalis; in no case was there evidence of squamous epithelium distributed within the adenohypophysis. It has been suggested that these nests of squamous epithelium serve as the precursors for the development of adamantinomatous type craniopharyngiomas (7).

Several lines of evidence suggest that the squamoid nests found in this adenoma are not simply pre‐existing squamous rests. First, the squamoid cell islands do not show the prototypical appearance of developmental squamous deposits of rests but have the morphological features of adamantinomatous craniopharyngioma with peripheral nuclear palisading and a focal stellate reticular appearance. Second, the squamoid epithelial cells are distributed randomly throughout the tumor suggesting that they have, in fact, developed in concert with the gonadotroph adenoma. They are not located at the edge of the tumor within preexisting pituitary stalk where they can often be found in normal pituitary glands. And thirdly, the positive immunostaining of the craniopharygioma for Ki‐67 (Figure F) suggests that these cells are proliferating and are not quiescent embryologic remnants. Based on this line of reasoning, we believe that this case represents a neoplastic proliferation expressing gonadotrophic adenoma with adamantinomatous type craniopharyngioma.

There are rare case reports of craniopharyngioma coexisting alongside a pituitary adenoma with those reported cases being prolactinomas 1, 3, 9. In these cases the two components represented geographically separate mass lesions. In the case reported here, the component showing craniopharyngioma differentiation is small, multifocal and intimately admixed with the pituitary adenoma. For discussion regarding the pathogenesis of this lesion please visit: http://path.upmc.edu/divisions/neuropath/bpath/cases/case169.html

Based on the data presented, we suggest that the nests of craniopharyngioma found in this pituitary adenoma represent islands of an unusual form of divergent differentiation in a pituitary adenoma 2, 4, 6, 8.

ABSTRACT

A 59 year‐old man presented with a large sellar mass. Pathologic examination revealed a tumor with two distinct cell populations. The majority of the tumor showed typical pituitary gonadotroph adenoma morphology and staining. Diffusely scattered throughout this tumor were nests of epithelial cells with an appearance typical of adamantinomatous craniopharyngioma and that were proliferating by Ki‐67. Moreover, their diffuse distribution within the adenoma portion of the tumor suggests that these areas arose from within the adenoma where squamous rests are not observed. While pituitary adenomas juxtaposed to craniopharyngiomas have been reported, these cases have consisted of distinct masses unlike the intimately admixed tumor described in this case. Moreover, all previous reports of craniopharyngiomas with pituitary adenoma have consisted of prolactinomas. This is the first reported case of a craniopharyngioma with gonadotroph adenoma.