Panhypopituitarism

* Primary pigmented intracranial neoplasms are strikingly uncommon. The differential diagnosis is limited and includes both epithelial and nonepithelial tumors, most of which arise within or near the ventricular system. The authors describe a 42-year-old man who presented with a pigmented papillary epithelial lesion that arose within the sella and exhibited suprasellar extension and bony erosion. Following external beam radiotherapy and multiple surgical resections, tumor growth became rapid, necessitating additional debulking procedures. Pathologic evaluation of subsequent lesional tissue samples revealed an anaplastic lesion with malignant epithelial and spindle cell components. Occasional epithelial cells showed features reminiscent of the original papillary lesion, whereas others exhibited oncocytic morphologic features. This case represents the only report, to our knowledge, of a pigmented papillary epithelial neoplasm arising within the pituitary fossa. Although the histogenesis of this tumor is enigmatic, this appears to be a distinct lesion characterized by aggressive growth and the capacity for anaplastic progression.

(Arch Pathol Lab Med. 2001;125:1242-1245)

Primary intracranial pigmented neoplasms are rare and include melanoma, melanocytoma, melanotic ependymoma, and subependymoma1; pigmented choroid plexus papilloma and carcinoma2-5; and melanotic astrocytoma.6 Most of these lesions arise within or in close proximity to the ventricular system. Herein, we describe the first case of a pigmented papillary epithelial neoplasm arising within the pituitary fossa, which in addition underwent anaplastic progression following multiple resections and radiation.

REPORT OF A CASE

Clinical Presentation and Treatment

A 42-year-old man presented with bitemporal hemianopsia and decreased visual acuity. Magnetic resonance imaging demonstrated a large mass that expanded the pituitary fossa with symmetrical lateral extension, producing bilateral cavernous sinus compression, and suprasellar extension. The dorsum sellae were eroded, but posterior and anterior extension of the tumor was minimal (Figure 1, A). The tumor enhanced strongly with intravenous gadolinium. Angiographic studies confirmed the prominent vascularity of the lesion. The patient underwent a transphenoidal tumor resection, followed by a course of external beam radiotherapy (5040 cGy). The panhypopituitarism and diabetes insipidus that resulted necessitated pharmacologic therapy..A second resection was performed 3 years later, followed by additional radiotherapy (3600 cGy).

During the next 2 years, the lesion progressed, extending into the sphenoid sinus and posterior nasal cavity, and a third resection was attempted by way of a combined subcranial anterior skull base, transethmoidal, and transphenoidal approach. Shortly thereafter, tumor growth accelerated, and imaging studies revealed tumor that extended deep into the nasal cavities and tracking along the underside of the frontal lobes (Figure 1, B). Gadolinium enhancement persisted, and there were numerous areas of necrosis. He received 2 courses of doxorubicin hydrochloride, but a poor response necessitated additional surgical debulking. The patient died several months later. Consent for autopsy was not obtained.

RESULTS

Histopathologic Findings

Microscopic evaluation of tissue from the first 3 resections showed a pigmented papillary neoplasm (Figure 2, A). The epithelial cells covering the fibrovascular cores were columnar, with bland oval nuclei that contained single nucleoli. Many contained granular, brown, Fontana-- positive pigment (removed after bleaching with potassium permanganate) indicative of melanin (Figure 2, B) and surface microvilli. Occasional cells had more abundant eosinophilic cytoplasm. Mitoses were rare. Mucin stains were negative, and the epithelial cells were immunopositive for transthyretin (TTR) (Figure 2, C), S100 protein, carcinoembryonic antigen, HMB-45 (Dako Corporation, Carpinteria, Calif), vimentin (Boehringer, Indianapolis, Ind), and CAM 5.2 (Becton Dickinson, San Diego, Calif). The stains were negative for all pituitary hormones (Signet, Dedham, Mass), pan-cytokeratin (AE1/AE3; Novacastra, Burlingame, Calif), epithelial membrane antigen (EMA), glial fibrillary acidic protein, chromogranin (Dako), and B72.3 (Signet).

Tissue obtained from subsequent debulking procedures was strikingly different from the original lesion. Histologic sections showed an anaplastic lesion composed of pleomorphic spindle cells that formed broad, haphazardly arranged fascicles that surrounded scattered epithelial islands (Figure 2, D), representing a poorly differentiated spindle cell carcinoma or carcinosarcoma. Focally, there remained papillary arrangements of epithelial cells on fibrovascular cores, but these cores now contained malignant spindle cells. Many of the epithelial cells contained abundant pink (oncocyte-like) granular cytoplasm, irregular-shaped nuclei, and macronucleoli. The spindle cells had indistinct cell boarders, elongated nuclei with coarse chromatin, and 1 or more macronucleoli. Occasional large bizarre cells were present, as were broad zones of necrosis. The mitotic rate of both cell morphologic components was brisk. Fontana and mucin stains were negative. In addition, TTR immunopositivity was seen in both cell components. Scattered epithelial cells retained the immunoprofile of the original papillary lesion; synaptophysin, placental alkaline phosphatase, desmin, muscle-specific actin (Dako), and neuron-specific enolase (BioGenex, San Ramon, Calif) were negative throughout.

Ultrastructural Findings

Electron microscopic examination of the original papillary lesion was limited by suboptimal fixation, though numerous ultrastructural features could be adequately elucidated. The epithelial cells contained oval nuclei with focally clumped chromatin and one electron-dense nucleolus. Specialized structures were present, including microvilli of varying length, desmosomes, and cell membrane interdigitations. Scattered cells contained abundant mitochondria. Basement membrane was focally identified. Granular material, often containing discrete electrondense central areas, was present, most likely representing neuromelanin (Figure 3, A). Secretory granules, melanosomes, and premelanosomes were absent.

Ultrastructural evaluation of the later, more anaplastic lesion revealed 2 distinct cell populations. The epithelial cells retained some characteristics of the original papillary lesion, including bulbous microvilli and occasional cell membrane interdigitation, though the nuclei were more convoluted and contained prominent macronucleoli (Figure 3, B). Several epithelial cells contained abundant mitochondria that corresponded to the oncocytic histomorphologic component, and neuromelanin was no longer discernible. The spindle cell population consisted of bipolar cells with large oval nuclei that contained macronucleoli and scattered rough endoplasmic reticulum, mitochondria, and lysosomes within their cytoplasm.

COMMENT

Our patient developed a distinctive central nervous system neoplasm that eventually underwent anaplastic progression. The original tumor, a pigmented papillary epithelial neoplasm, arose within the pituitary fossa and was associated with surrounding bony erosion and suprasellar extension. The differential diagnosis of pigmented intracranial neoplasms is limited. Given the epithelial nature of the current lesion, multiple entities are eliminated, including melanoma, melanocytoma, pigmented astrocytoma, and subependymoma. This leaves several possibilities as to the histogenesis, all of which may exhibit epithelial and/or papillary morphologic components.

First on the list is the pigmented choroid plexus papilloma. Three such lesions, replete with neuromelanin, have been described in the medical literature. One tumor arose within the lateral ventricle,3 whereas the other 2 cases originated within the fourth ventricle.2,4 Our tumor demonstrated TTR-positive, EMA-negative columnar epithelial cells with surface microvilli and an underlying basement membrane, characteristic of most choroid plexus lesions. It should be pointed out, however, that TTR is not entirely specific for choroid plexus neoplasms, since TTR immunoreactivity has been documented in several other neoplasms, retinal pigment epithelium, and hepatocytes.7 Additionally, primary extraventricular locations for choroid plexus-derived lesions are uncommon, with only one such tumor described arising in the suprasellar region.8 There is a possibility that our tumor may have in fact arisen from the floor of the third ventricle; however, this seems unlikely given the extensive bony erosion of the sella and the fact that no definite intraventricular component was demonstrated. Although the current lesion likely represents an atypical pigmented choroid plexus tumor arising from an ectopic remnant, this would be an unusual site and presentation for an already rare tumor.

There are several additional papillary lesions that should be considered. Papillary ependymomas, including rare pigmented examples; typically show perivascular pseudorosettes and immunopositivity for glial fibrillary acidic protein, which was not seen in our case. Ependymomas also are TTR negative, and the neoplastic cells do not rest on a basement membrane. Regarding papillary pituitary adenoma, secretory granules are commonplace, and one would expect to find immunoreactivity for synaptophysin and chromogranin as opposed to TTR and S100 protein. Furthermore, no pigmented pituitary adenomas, to our knowledge, have been reported. Papillary adenocarcinoma could arise within the sella as a primary lesion from ectopic salivary gland remnants in the pars intermedia or from sinus-type mucosa as in the Rathke pouch9 or as a metastasis. In either scenario, adenocarcinomas typically show strong anticytokeratin and EMA immunoreactivity and more atypical cytomorphologic structure; S100 protein expression would be somewhat unusual. Cytokeratins 7 and 20, which were not performed in this case, are unlikely to add pertinent information, since positivity for both of these antibodies is variable in choroid plexus lesions, potentially resembling the immunophenotype of numerous other carcinomas.10 The locally aggressive clinical course in this patient also speaks against a metastatic origin, and likewise it would be rare to have a solitary metastasis lasting 6 years without the primary lesion declaring itself.

Cells with an oncocytic cytomorphologic component were also present in this tumor, and care should be taken to rule out lesions that contain histologically similar cells. Oncocytomas may arise in the sella9 and, as their name implies, are solely composed of sheets of oncocytic cells. Likewise, granular cell tumors may arise in relation to the pituitary gland/stalk; however, these tumors owe their cytoplasmic granularity to numerous autophagic vacuoles, not mitochondria.

The carcinosarcoma that developed later in this patient showed no characteristics of any particular mesenchymal element; furthermore, the epithelial component retained many similarities to the original papillary lesion, although anaplasia and mitotic activity indicate progression to a higher-grade lesion. Taken together, we believe the transformed lesion in this patient represents an anaplastic carcinoma with spindled elements (eg, spindle cell carcinoma, carcinosarcoma, or metaplastic carcinoma). Whether malignant progression occurred as a result of radiation or despite it is uncertain, although the latter is more likely given the course presented.

In conclusion, we describe a case of a pigmented papillary epithelial neoplasm arising within the pituitary fossa. This distinct lesion, although extremely rare, should be included in the differential diagnosis of tumors that might arise in this location. Furthermore, this case demonstrates the potential for these lesions to undergo malignant transformation, making clinical treatment extremely challenging. Additional experience will be needed to further characterize this unusual entity.

We thank Dr A. Rosenbaum for his input regarding radiographic imaging and Ms M. Barcza, Ms Donna Barrett, and Mr John Daucher for their technical expertise. We also thank Drs A. Perry B. W Scheithauer, M. Rooney, and G. Collins for their pathologic consultation on this case.

References

1. Rosenblum MK, Erlandson RA, Aleksic SN, Budzilovich GN. Melanotic ependymoma and subependymoma. Am J Surg Pathol. 1990;14:729-736.

2. Caccamo DV, Ho KL, Garcia JH. Cauda equina tumor with ependymal and paraganglionic differentiation. Hum Pathol. 1992;23:835-838.

3. Reimund EL, Sitton IF, Harkin JC. Pigmented choroid plexus papilloma. Arch Pathol Lab Med. 1990;114:902-905.

4. Watanabe K, Ando Y, Iwanaga H, et al. Choroid plexus papilloma containing melanin pigment. Clin Neuropathol. 1995;14:159-161.

5. Dobin SM, Donner LR. Pigmented choroid plexus carcinoma: a cytogenetic and ultrastructural study. Cancer Genet Cytogenet. 1997;96:37-41.

6. Vajtai I, Yonekawa Y, Schauble B, Paulus W. Melanotic astrocytoma. Acta Neuropathol (Berl). 1996;91:549-553.

7. Albrecht S, Bayre TA, Kraus JA, Pietsch T. Transthyretin expression in medulloblastomas and medulloblastoma cell lines. Neuropathol Appl Neurobiol. 1995;21:399-409.

8. Kimura M, Takayasu M, Suzuki Y, et al. Primary choroid plexus papilloma located in the suprasellar region: case report. Neurosurgery. 1992;31:563-566.

9. Hampton TA, Scheithauer BW, Rojiani AM, Kovacs K, Horvath E, Vogt P. Salivary gland-like tumors of the sellar region. Am J Surg Pathol. 1997;21:424-- 434.

10. Gyure KA, Morrison AL. Cytokeratin 7 and 20 expression in choroid plexus tumors: utility in differentiating these neoplasms from metastatic carcinomas. Mod Pathol. 2000;13:638-643.

Christine E. Fuller, MD; Mark Smith, MD; Douglas C. Miller, MD, PhD; Robert Schelper, MD, PhD

Accepted for publication March 22, 2001.

From the Departments of Anatomic Pathology (Drs Fuller and Schelper) and Neurosurgery (Dr Smith), State University of New York Upstate Medical University, Syracuse, NY, and Department of Pathology, Division of Neuropathology, New York University School of Medicine, New York, NY (Dr Miller).

This case report ("Postirradiation sarcomatous transformation in a pigmented papillary sellar lesion: a radiographic, histologic, immunohistochemical, and ultrastructural study" by Drs Fuller and Schelper) was previously presented in poster format at the 74th Annual Meeting of the American Association of Neuropathologists, Minneapolis, Minn, June 18-21, 1998.

Reprints: Christine E. Fuller, MD, Department of Pathology, Washington University at St Louis, Campus Box 8118, 660 S Euclid Ave, St Louis, MO 63110 (e-mail: fullercny@hotmail.com).

Copyright College of American Pathologists Sep 2001
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