Brain Pathology Case of the Month - December 1998

FINAL DIAGNOSIS:     Rathke's Cleft Cyst

DISCUSSION:

Remnants of Rathke's cleft persist as microcysts at the interface of the adenohypophysis and neurohypophysis. They are usually incidental postmortem or radiographic findings (3) Occasionally they may enlarge and become symptomatic in the form of headaches, visual disturbances, or pituitary dysfunction. Symptomatic cysts have usually been reported in adults, and rarely in the pediatric population (4).

Radiographically, Rathke's cleft cysts usually are smooth bordered, homogeneous, and do not contrast enhance. High signal intensity on T1 weighted MRI images has been reported in cysts with hemorrhage, hemosiderin pigment, and cholesterol clefts (6). Rathke's cleft cysts may enhance peripherally as the result of inflammation and granulation tissue within the cyst wall (2,4,6). Others have disputed this, and claim the peripheral enhancement is due to a peripherally displaced rim of pituitary tissue (5).

The inflammatory process seen in some cases may represent a foreign body reaction to leakage of cyst contents, such as mucin, from partial rupture of the cyst (1,7). Other rare inflammatory lesions of the sellar region include lymphocytic hypophysitis, tuberculosis, syphilis, and sarcoidosis (8). Rathke's cleft cysts have been reported in association with abscess formation, in which the cysts were infected by the hematogenous spread of bacteria (2).

The pre-operative differential diagnosis in this case, based on clinical data and imaging, was pituitary adenoma or craniopharyngioma. There was no evidence of epithelial lobules with peripheral palisading, dystrophic calcification, or necrobiotic squamous debris, to suggest the diagnosis of craniopharyngioma. The finding of cholesterol crystals and hemosiderin pigment should alert the pathologist to carefully exclude the diagnosis of craniopharyngioma, although a ruptured Rathke's cleft cyst should also be considered.

REFERENCES

  1. Albini CH, MacGillivray MH, Fisher JE, Voorhess ML, Klein DM. (1988) Triad of Hypopituitarism, Granulomatous Hypophysitis, and Ruptured Rathke's Cleft Cyst. Neurosurgery 22: 133-136
  2. Bognar L, Szeifert GT, Fedorcsak I, Pasztor E. (1992) Abscess Formation in Rathke's Cleft Cyst. Acta Neurochir 117: 70-72
  3. Burger PC, Scheithauer BW (1994) Atlas of Tumor Pathology: Tumors of the Central Nervous System, Third Series, Armed Forces Institute of Pathology, Washington D.C. pp 357-359.
  4. Christophe C, Flamant-Durand J, Hanquinet S, Heinrichs C, Raftopoulos C, Sariban E, Segebarth C, Perlmutter N. (1993) MRI in seven cases of Rathke's cleft cyst in infants and children. Pediatr Radiol 23:79-82
  5. Naylor MF, Scheithauer BW, Forbes GS, Tomlinson FH Young WF. (1995) Rathke Cleft Cyst: CT, MR, and Pathology of 23 Cases. J Comput Assist Tomogr 19 (6) 853-859.
  6. Oka H, Kawano N, Suwa T, Yada K, Kan S, Kameya T. (1994) Radiological Study of Symptomatic Rathke's Cleft Cysts. Neurosurgery 35 (4) 632-637.
  7. Roncaroli F, Bacci A, Frank G, Calbucci F. (1998) Granulomatous Hypophysitis Caused by a Ruptured Intrasellar Rathke's Cleft Cyst: Report of a Case and Review of the Literature. Neurosurgery 43 (1) 146-149.
  8. Wearne MJ, Barber PC, Johnson AP. (1995) Symptomatic Rathke's cleft cyst with hypophysitis. Br J Neurosurg 9: 799-803

Contributed by Thomas J Cummings MD, Charleen T Chu MD, PhD, Christine M Hulette MD

International Society of Neuropathology