Background: In Rathke cleft cysts (RCCs), inflammation by the cyst contents infrequently spreads to the surrounding structures. Calcification, which is regarded as a result of chronic inflammation of the cyst wall, can rarely be found in RCCs. Moreover, ossification is extremely rare.
Case description: A 60-year-old woman experienced headaches, fatigue, and weight loss owing to pan-hypopituitarism. Magnetic resonance imaging revealed a mass lesion in the sellar region, which was composed of two different parts, with hypointensity anteriorly and hyperintensity posteriorly on T1-weighted image, and the rim with significant hypointensity entirely on T2-weighted image. During the transsphenoidal surgery, the cyst wall was so rigid that it was difficult to cut and remove it. The cyst contained mucinous fluid with both old and new hemorrhages, and a yellowish, elastic hard, solid nodule. Postoperative histologic diagnosis was RCC with unusual lymphocyte infiltration, massive granulation, and mature bone formation. Six months later, the fluid in the cyst reaccumulated, and the patient complained of headaches. Removal of the entire cyst wall and the aspiration of the cyst content were performed to collapse the cyst cavity and, consequently, to prevent further recurrence. Postoperatively, panhypopituitarism was unchanged and the symptoms were treated with hormonal replacement. The cyst has not recurred for 2 years after the second surgery.
Conclusions: Persistent, long-term inflammation induced by the RCC content, mucin-containing fluid, and several phases of hemorrhage presumably promoted the formation of mature bone on the cyst wall and of the elastically solid nodule within the cyst.
Keywords: Inflammation; Metaplasia; Nodule; Ossification; Rathke cleft cyst.
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