Intrasellar Epithelial Cysts

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The subject of cystic lesions in, around, and above the sella turcica has at times been confusing from the standpoint of the neurosurgeon, who is particularly concerned with the nature of a lesion at the time of its operative exposure and how radical must be its excision. Cystic adenomas of the pituitary present very little problem. They are usually readily identified, clearly contain tumor tissue and are treated as neoplasms. The delineation of other cysts is sometimes difficult and confusion is compounded by pathological terminology. Thus, the so-called craniopharyngiomatous cyst contains cholesterin crystals, while the cholesteatoma or epidermoid

The subject of cystic lesions in, around, and above the sella turcica has at times been confusing from the standpoint of the neurosurgeon, who is particularly concerned with the nature of a lesion at the time of its operative exposure and how radical must be its excision. Cystic adenomas of the pituitary present very little problem. They are usually readily identified, clearly contain tumor tissue and are treated as neoplasms. The delineation of other cysts is sometimes difficult and confusion is compounded by pathological terminology. Thus, the so-called craniopharyngiomatous cyst contains cholesterin crystals, while the cholesteatoma or epidermoid actually contains keratohyalin granules and lacks cholesterin. The term craniopharyngioma, which has gained acceptance, is probably a poor name for this lesion, since Rathke's pouch develops from the stomodeum and not from pharyngeal elements. The major problem which confronts the surgeon and clinical pathologist is that of distinguishing between a craniopharyngioma with cyst formation (hypophysial stalk) and an intrasellar epithelial cyst, which is actually a cyst of the pituitary gland.

The epithelial cyst is a rare lesion, and its relation to the suprasellar cyst is questionable but in the past they have usually been grouped together with the thought that all are perhaps in some way derived from remnants of Rathke's pouch. The pouch itself closes early in embryonic life, but its apical extremity persists in postnatal life as a cleft between the anterior and posterior lobes of the hypophysis (Fig. 1). The cleft is lined with cuboidal or columnar epithelium often ciliated in places and at times it also contains mucous goblet cells (Fig. 2). Thus the background is set for the development of a cyst within this cleft. Epidermoid cysts at the level of the stalk, however, have been traced to small nests of squamous cells, also remnants of Rathke's pouch. This is understandable in view of the rotation of the anterior pituitary upward and forward early in its development.

Fig. 1.
Fig. 1.

The residual embryonic lumen between anterior and posterior lobes which becomes a cleft in the pituitary gland (A) at 8 weeks (B) at 11 weeks. (From Arey, L.B.: Developmental Anatomy: A Textbook and Laboratory Manual of Embryology. Philadelphia: W. B. Saunders Co., 1954, 6th ed. p. 200.)

Fig. 2.
Fig. 2.

Normal pituitary gland showing Rathke's cleft. A few colloid-filled spaces can be seen; ×7.

Several anatomists and pathologists—among them Russell and Rubenstein,7 Hunter,4 and Willis12 have given attention to the development of cystic change in Rathke's cleft. Shanklin,8–10 in his several papers on the subject, cited Luschka's description in 1860 of epithelial areas in the capsule of the human hypophysis which resembled oral mucosa. Shanklin examined 100 pituitary glands and actually found cysts in 13 of these. The glands were taken from persons who ranged in age from 11 to 20 years. He classified the cysts as cystic clefts (partial or complete) and follicular cysts (simple, compound or multiple). One of us (H. C.) examined 40 pituitary glands obtained at necropsy and found 2 which contained cystic change. One was a dilatation of the cleft lined by low cuboidal epithelium and the other appeared within the anterior lobe (Fig. 3).

Fig. 3.
Fig. 3.

(A) Dilatation of cleft filled with colloid and lines by cuboidal epithelium in an otherwise normal pituitary gland; ×7. (B) Cyst within anterior lobe. Focal areas of lining contained cilia; ×7.

However, cysts of macroscopic dimension projecting upward from the sella have been reported very infrequently in the clinical literature, and one wonders whether they have perhaps been more prevalent and were erroneously diagnosed as craniopharyngiomas. Frazier and Alpers3 made the distinction in their case. The cyst wall was a bluish membrane; 8 cc. of brownish fluid was evacuated and no solid tissue was found within the cyst. The lining was composed of ciliated columnar epithelium in a single layer. In a subsequent review, these authors specifically included mucoid epithelial cysts which they referred to as cysts of Rathke's cleft. Bailey1 included mucoid epithelial cysts in his classification of pituitary lesions. Smith and Bucy11 provided a clinical and pathologic description of a mucoid cyst treated by surgery, and Rowbotham and Clarke6 subsequently reported a similar case. The most recent case was that reported by Fairburn and Larkin;2 their patient had a typical chiasmal syndrome. At operation a large, intrasellar cyst was found. Thick, purulentlooking material was evacuated, following which a smooth-walled cystic cavity was found to occupy practically all of the pituitary fossa. The patient made a full recovery and was well at the time of their report 4 years later. It is important to note that in this, as well as in most of the other cases, the cyst wall itself was not removed except for the biopsy portion. Love and Kernohan5 mentioned one case, but most of the reports dealing with epidermoid tumors and craniopharyngiomas do not differentiate these from epithelial cysts, although instances of the latter may quite possibly be included in some of these series.

In 1963 a patient came to our attention whose lesion resembled several others seen in recent years, and stimulated a closer look at these cases which had been variously diagnosed as cyst of a craniopharyngeal remnant, epithelial inclusion cyst, epithelial unclassified cyst, and mucocele.

Case Report

A 59-year-old woman was first seen in September, 1963, because of a 6 months' history of progressive loss of peripheral vision, worse on the left side. She found it hard to read the left hand side of the newspaper. At another hospital in June, 1963, she had had a lumbar puncture, left carotid arteriogram, skull roentgenograms, and a scanning procedure, all reported normal. Four years previously, she had noticed slight increase in thirst and urination, which had persisted. Her past history was significant only in that she had a panhysterectomy and oophorectomy when 30 years old and therefore no menstrual history behond that time.

Examination showed slight pallor, smooth skin, scanty axillary hair, and a chiasmal syndrome with bitemporal visual field defects. Although she appeared to be in a mildly hypopituitary state and had a hemoglobin of 9 gm., the 17-hydroxycorticosteroids, 17-ketosteroids, and radioactive iodine uptake were all normal. A pneumoencephalogram showed good filling above what appeared to be a normal sella turcica, but a carotid arteriogram showed suprasellar extension of a lesion beneath the anterior cerebral arteries.

Operation. A thin-walled cyst was found that severely compressed both nerves and the chiasm. It occupied the entire sella and extended above. The fluid material within the cyst was thick, white, and mucoid, but could be aspirated with a number 18 gauge needle. About 7 to 8 cc. was obtained. The cyst was then opened widely, evacuated, and dissected away from the chiasm. The pituitary stalk was not seen nor could any solid tissue be found within the cyst or in its wall. It was shrunken by coagulation and partially excised; a large portion was left within the anterior sella in the hope that this might be the area of functioning, compressed pituitary tissue.

The postoperative course was complicated by a serious electrolyte imbalance and mild diabetes insipidus (there was a marked hypernatremia with sodium levels as high as 164 mEq.) but these proved to be reversible in about 2 to 3 weeks. The cyst wall on pathologic study proved extremely thin and was lined with cuboidal epithelium. In some places it had a columnar and pseudo-stratified appearance (Fig. 4).

Fig. 4.
Fig. 4.

Cyst lining of pseudostratified columnar epithelium; ×350.

Discussion

Since 1956, 5 patients with intrasellar epithelial cysts of this type have come under observation. Four of them have been operated on by one of us (C. A. F.) and one by Dr. James L. Poppen. All of the pathologic material has been reviewed (H. C.), although in a few cases there was very little tissue to work with. In 4 of the patients the cyst contained mucous or mucoid material. In 1 the fluid was liquid brown and contained a few cholesterin crystals, but the lesion was entirely cystic, and contained no solid tissue. The patient's history had begun 6 years before with left temporal hemianopsia. In 1 patient the lesion was quite large and at the time of surgery was thought to be a mucocele, but no connection with the sphenoid sinus could be demonstrated. Except for 1, all of the patients had visual loss severe enough to justify operation; in 1 patient an abortive attempt was made at x-ray therapy. Headache, visual symptoms, or amenorrhea in all of the patients dated back 4 to 10 years, but in each case there was recent deterioration of vision. All of the patients were women.

The cysts varied considerably in size. Some produced little change in the sella while others showed moderate suprasellar extension or even massive erosion of the sella (Fig. 5).

Fig. 5.
Fig. 5.

(A) Advanced destruction of sella by large long-standing cyst. (B) Carotid arteriogram of same patient, showing widening of ‘siphon.’ This patient had no visual loss.

Pathologically, the lining membranes also varied from flattened epithelium (Fig. 6) to low cuboidal and columnar types (Fig. 7). In one of the specimens, it was possible to demonstrate mucous-secreting glands (Fig. 8).

Fig. 6.
Fig. 6.

Flattened epithelium lining one of the cysts; ×350.

Fig. 7.
Fig. 7.

Cuboidal type of epithelial lining; ×350.

Fig. 8.
Fig. 8.

Mucous-secreting glands found in one of cases described; ×350.

Figure 9 shows that the prognosis with this type of cystic lesion obviously is better than with craniopharyngioma or suprasellar main at the periphery of the cyst within the sella. The gross appearance of mucoid material within the cyst seems the simplest confirmation at the time of operation. If no solid tissue is found within the cyst cavity, this is presumptive evidence of an epithelial cyst, and pathologic verification should be made from a biopsy of the cyst wall. The cyst should be fully evacuated and a liberal opening made in the wall to prevent loculation cyst. In none of the 5 cases was the cyst wall completely removed, yet the longest follow-up period has now been 9 years, and there has been no recurrence of symptoms in any of the patients. This certainly confirms the pathologic impression that the lesion is not neoplastic. One can surmise that a gradual increase in the size of the cyst results from slow elaboration of mucoid fluid expanding its content. From a practical standpoint, it becomes important to emphasize accuracy of diagnosis at the time of surgery and a less radical approach to the lesion. Total excision seems to be not only unnecessary but undesirable because of the likelihood of removing functioning pituitary tissue that may reand reaccumulation of fluid, although this possibility is only speculative. The diagnosis of this type of cystic lesion should be considered in any patient suspected of having a pituitary adenoma and whose vision fails to improve with x-ray therapy.

Fig. 9.
Fig. 9.

Visual fields and acuity. All patients are still well with no change in postoperative visual findings.

Summary

Five patients with intrasellar epithelial cysts have undergone successful surgical treatment which involved simple evacuation of the cyst contents. These cystic lesions may be more common than is indicated by the paucity of previous reports. Their origin from Rathke's cleft is fairly well established. There appears to be a clear pathologic distinction between these cysts and those of the craniopharyngiomatous type arising from squamous cell rests in the hypophysial stalk. The favorable prognosis makes their identification at the time of surgery important in order to avoid a more radical operation. The most useful identifying feature is the characteristic appearance of the mucoid cystic contents, described in 4 of the 5 reported cases.

References

  • 1.

    BaileyP. Tumors of the hypophysis cerebri. In: Cytology and cellular pathology of the nervous system. W. PenfieldEd. New York: P. B. Hoeber, Inc.19233: 11311144.BaileyCytology and cellular pathology of the nervous system.3: 1131–1144.

  • 2.

    FairburnB.LarkinI. M. A cyst of Rathke's cleft. J. Neurosurg.196421: 223225.FairburnLarkinJ. Neurosurg.21: 223–225.

  • 3.

    FrazierC. H.AlpersB. J. Tumors of Rathke's cleft (hitherto called tumors of Rathke's pouch). 193432: 973984.FrazierAlpers32: 973–984.

  • 4.

    HunterI. J. Squamous metaplasia of cells of the anterior pituitary gland. J. Path. Bact.195569: 141145.HunterJ. Path. Bact.69: 141–145.

  • 5.

    LoveJ. G.KernohanJ. W. Dermoid and epidermoid tumors (cholesteatomas) of central nervous system. J. Amer. med. Ass.1936107: 18761882.LoveKernohanJ. Amer. med. Ass.107: 1876–1882.

  • 6.

    RowbothamG. F.ClarkeP. R. R. Colloid cyst of the pituitary gland causing chiasmal compression. Brit. J. Surg.195644: 107108.RowbothamClarkeBrit. J. Surg.44: 107–108.

  • 7.

    RussellD. S.RubinsteinL. J. Pathology of tumours of the nervous system. London: E. Arnold Ltd.1959318 pp.RussellRubinsteinPathology of tumours of the nervous system.

  • 8.

    ShanklinW. M. On the presence of cysts in the human pituitary. Anat. Rec.1949104: 379407.ShanklinAnat. Rec.104: 379–407.

  • 9.

    ShanklinW. M. The histogenesis and histology of an integumentary type of epithelium in the human hypophysis. Anat. Rec.1951109: 217231.ShanklinAnat. Rec.109: 217–231.

  • 10.

    Shanklin W. M. The incidence and distribution of cilia in the human pituitary with a description of micro-follicular cysts derived from Rathke's cleft. Acta Anat.195111: 361382.Shanklin W. M. The incidence and distribution of cilia in the human pituitary with a description of micro-follicular cysts derived from Rathke's cleft. Acta Anat.11: 361–382.

  • 11.

    SmithR. A.IIIBucyP. C. Pituitary cyst lined with a single layer of columnar epithelium. J. Neurosurg.195310: 540543.SmithBucyJ. Neurosurg.10: 540–543.

  • 12.

    WillisR. A. The borderland of embryology and pathology. London: utterworth & Co.1958ix627–33 pp. (see pp. 266269).WillisThe borderland of embryology and pathology.

Article Information

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Headings

Figures

  • View in gallery

    The residual embryonic lumen between anterior and posterior lobes which becomes a cleft in the pituitary gland (A) at 8 weeks (B) at 11 weeks. (From Arey, L.B.: Developmental Anatomy: A Textbook and Laboratory Manual of Embryology. Philadelphia: W. B. Saunders Co., 1954, 6th ed. p. 200.)

  • View in gallery

    Normal pituitary gland showing Rathke's cleft. A few colloid-filled spaces can be seen; ×7.

  • View in gallery

    (A) Dilatation of cleft filled with colloid and lines by cuboidal epithelium in an otherwise normal pituitary gland; ×7. (B) Cyst within anterior lobe. Focal areas of lining contained cilia; ×7.

  • View in gallery

    Cyst lining of pseudostratified columnar epithelium; ×350.

  • View in gallery

    (A) Advanced destruction of sella by large long-standing cyst. (B) Carotid arteriogram of same patient, showing widening of ‘siphon.’ This patient had no visual loss.

  • View in gallery

    Flattened epithelium lining one of the cysts; ×350.

  • View in gallery

    Cuboidal type of epithelial lining; ×350.

  • View in gallery

    Mucous-secreting glands found in one of cases described; ×350.

  • View in gallery

    Visual fields and acuity. All patients are still well with no change in postoperative visual findings.

References

1.

BaileyP. Tumors of the hypophysis cerebri. In: Cytology and cellular pathology of the nervous system. W. PenfieldEd. New York: P. B. Hoeber, Inc.19233: 11311144.BaileyCytology and cellular pathology of the nervous system.3: 1131–1144.

2.

FairburnB.LarkinI. M. A cyst of Rathke's cleft. J. Neurosurg.196421: 223225.FairburnLarkinJ. Neurosurg.21: 223–225.

3.

FrazierC. H.AlpersB. J. Tumors of Rathke's cleft (hitherto called tumors of Rathke's pouch). 193432: 973984.FrazierAlpers32: 973–984.

4.

HunterI. J. Squamous metaplasia of cells of the anterior pituitary gland. J. Path. Bact.195569: 141145.HunterJ. Path. Bact.69: 141–145.

5.

LoveJ. G.KernohanJ. W. Dermoid and epidermoid tumors (cholesteatomas) of central nervous system. J. Amer. med. Ass.1936107: 18761882.LoveKernohanJ. Amer. med. Ass.107: 1876–1882.

6.

RowbothamG. F.ClarkeP. R. R. Colloid cyst of the pituitary gland causing chiasmal compression. Brit. J. Surg.195644: 107108.RowbothamClarkeBrit. J. Surg.44: 107–108.

7.

RussellD. S.RubinsteinL. J. Pathology of tumours of the nervous system. London: E. Arnold Ltd.1959318 pp.RussellRubinsteinPathology of tumours of the nervous system.

8.

ShanklinW. M. On the presence of cysts in the human pituitary. Anat. Rec.1949104: 379407.ShanklinAnat. Rec.104: 379–407.

9.

ShanklinW. M. The histogenesis and histology of an integumentary type of epithelium in the human hypophysis. Anat. Rec.1951109: 217231.ShanklinAnat. Rec.109: 217–231.

10.

Shanklin W. M. The incidence and distribution of cilia in the human pituitary with a description of micro-follicular cysts derived from Rathke's cleft. Acta Anat.195111: 361382.Shanklin W. M. The incidence and distribution of cilia in the human pituitary with a description of micro-follicular cysts derived from Rathke's cleft. Acta Anat.11: 361–382.

11.

SmithR. A.IIIBucyP. C. Pituitary cyst lined with a single layer of columnar epithelium. J. Neurosurg.195310: 540543.SmithBucyJ. Neurosurg.10: 540–543.

12.

WillisR. A. The borderland of embryology and pathology. London: utterworth & Co.1958ix627–33 pp. (see pp. 266269).WillisThe borderland of embryology and pathology.

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