SCO was first described by Roncaroli et al
. as a tumor containing fascicles of spindle cells with eosinophilic, granular cytoplasm, and a distinct immunophenotype which includes positive immunoreaction to vimentin, EMA, S-100, and galectin-3 with negative immunoreactions to pituitary hormones, synaptophysin, chromogranin, and cytokeratins. They suggested a benign nature based on the absence of cellular anaplasia, mitoses, and necrosis along with a low Ki-67 proliferation labeling index, and that no recurrence was observed in all five cases of their series with a mean follow-up of 3 years.[27
However, more recently a further nine additional cases have been described, six of which recurred.[2
] Two recurrent cases described by Kloub et al
. demonstrated a high Ki-67 labeling index and one of these had mitosis and necrosis. Four cases demonstrated a low Ki-67 labeling index and showed no mitosis or necrosis. Our case also recurred 9 months after the partial resection, which showed a low Ki-67 labeling index (5%) without mitosis or necrosis. The mean time between the surgery and recurrence of seven cases including our case was 3.3 years (ranging from 5 months to 13 years). Six out of 7 (85.7%) recurrent cases underwent an incomplete resection at the original surgery. The incomplete resection of the tumor was a significant risk factor for recurrence (P
= 0.0014; ). Seven out of 8 cases with a total resection did not recur (mean follow-up, 5.1 years).
Recurrence-free survival curve of reported cases of spindle cell oncocytoma indicating an incomplete resection of the tumor was a significant risk factor for recurrence (P= 0.0014)
The previous report described SCOs as firm, fibrous, and adherent to surrounding structures making dissection difficult especially in recurrent cases.[8
] These tumors have also been described as highly vascular.[8
] These characteristics were also observed in our case, and when present, can negatively impact the ability to carry out a complete resection.
Pituicytoma is a rare, solid, glial, and low-grade tumor of adult pituitary. Histologically, pituicytoma consists of elongate, bipolar spindle cells arranged in interlacing fascicles or assuming a storiform pattern.[4
] Mitotic figures are absent or rare. Immunohistologically, they show positivity for vimentin, S-100 protein and, to a variable degree, GFAP. In contrast to spindle cell oncocytoma, EMA is usually negative. Due to their slow growth and the possibility of curative surgery, pituicytomas correspond to WHO grade I.[11
Of 29 cases of pituicytoma with a detailed follow-up, 6 cases (20.7%) recurred. The Ki-67 labeling index was low and mitosis or necrosis was not observed in any recurrent case. The mean time between the original surgery and recurrence was 1.1 years (ranging from 5 months to 2 years). All the recurrent cases underwent an incomplete resection at the original surgery. Similar to SCO, an incomplete resection of the tumor was a significant risk factor for recurrence (P = 0.019; ). Six out of 16 cases (37.5%) with an incomplete resection recurred. All 13 cases with a total resection did not have recurrence (mean follow-up, 2.0 years).
Recurrence-free survival curve of reported cases of pituicytoma indicating an incomplete resection of the tumor was a significant risk factor for recurrence (P= 0.019)
Pituicytomas have also been described as highly vascular like SCOs,[1
] which also applied in our pituicytoma case, and when present, may preclude complete resection.
The immunostain by S-100 was positive in all the reported cases of SCOs and pituicytomas. GFAP positivity varied in pituicytomas. The immunostain by GFAP was available in 38 cases of pituicytoma, of which 9 cases (23.7%) were negative for GFAP. The immunostain by galectin-3 was positive in our cases of SCO and pituicytoma. Rodríguez et al
. showed that galectin-3 is expressed not only in SCO but also in pituicytoma and granular cell tumors. And they suggested that this marker is of little use to differentiate those diagnoses.[25
] Lee et al
. recently reported that TTF-1 is specifically expressed in pituicytoma, granular cell tumors, and SCO, and it is useful for distinguishing them from other sellar tumors.[20
] Those markers (S-100, GFAP, TTF-1, and galectin-3) seem to have limitations to differentiate SCO and pituicytoma.
In all 15 reported cases of SCO, the immunostain by EMA was available and showed positivity in every case. The immunostain by EMA was available in 32 cases of pituicytoma. EMA was negative in 28 (87.5%) cases and only focally positive in 4 cases. Therefore, EMA is considered to be important to distinguish these tumors.
There is little evidence for the sensitivity of SCOs to radiotherapy. Four of five SCO cases which underwent radiation therapy recurred.[3
] There also are limited data on radiotherapy for pituicytomas. Therefore, at the current time, no recommendations can be made regarding the effectiveness of adjuvant radiotherapy for these tumors. The effectiveness of stereotactic radiosurgery for these pathologies is not described previously. Based on our report and the literature, relative to other benign sellar lesions including meningioma, pituitary adenoma, and craniopharyngioma, radiosurgery appears to be a reasonable consideration for small-volume tumors not effacing or encasing the optic apparatus.