Clinical Significance of Granulation Pattern in Corticotroph Pituitary Adenomas
Sema ÇÝFTÇÝ DOÐANÞEN1, Bilge BILGIÇ2, Gülþah YENIDÜNYA YALIN1, Seher TANRIKULU1, Sema YARMAN1
1Department of Internal Medicine, Division of Endocrinology and Metabolism, Istanbul University, Istanbul Faculty of Medicine, ISTANBUL, TURKEY
2Department of Pathology, Istanbul University, Istanbul Faculty of Medicine, ISTANBUL, TURKEY
Keywords: Cushing’s disease, Corticotroph tumor, Densely granulated, Sparsely granulated, Recurrence
The granulation pattern of pituitary tumors may be important to predict tumor behavior, treatment outcomes, and recurrences.
Therefore, we compared densely granulated corticotroph tumor (DGCT) and sparsely granulated corticotroph tumor (SGCT) in terms of
Material and Method: A total of 41 patients (31 females/10 males) were assessed in the study. The granulation patterns were detected by Periodic
Acid-Schiff (PAS) and adrenocorticotropic hormone (ACTH) immunoreactivity. Diffuse and strong staining by PAS and ACTH were identified
as DGCT, whereas faint staining by PAS and focal, weak staining by ACTH were identified as SGCT. Perinuclear ring-like patterns with low
molecular weight keratin were identified as Crooke’s cell tumors. DGCTs and SGCTs were compared in terms of clinical findings and treatment
Results: The majority of the patients (71%) had DGCTs (n=29); whereas 24% of the patients had SGCTs (n=10) and 5% of the patients had
Crooke’s cell tumors (n=2). DGCTs and SGCTs were similar in terms of age, sex, estimated duration of disease, baseline cortisol and ACTH levels.
SGCTs were larger than DGCTs (p=0.034). The remissions with surgery rates were similar between the groups; however, hypothalamic-pituitaryadrenal
axis recovery time was longer in SGCTs (p=0.033). Persistent disease after surgery was slightly higher in DGCTs and recurrences were
frequent in SGCTs; however, the differences were not statistically significant.
Conclusion: DGCTs are often small microadenomas, while SGCTs are larger. Recurrences were slightly more common in SGCTs; however,
further studies including larger series are needed to be able to obtain more significant results.
Cushing’s disease (CD) is an aggressive endocrine disorder
caused by a pituitary tumor secreting adrenocorticotrophic
hormone (ACTH) and may lead to significant morbidity
and mortality 1
. Despite significant advances in the
physiopathology and treatment options, there are still
many challenges in the management of CD. The primary
treatment is surgery; however, persistent disease and
recurrences after the surgery are common 2
Histological findings in the specimens obtained from
surgery and the granulation pattern of the tumors may
help predict disease recurrence 3. Although corticotroph
tumors have not been classified in accordance with
granulation patterns in the World Health Organization
(WHO) 2004 criteria, dense and sparse granulation patterns
of prolactinomas and somatotroph tumors have widely been identified 4. For this reason, granulation patterns of
corticotroph tumors have been included in the latest World
Health Organization classification in 2017 5. In line with
this, corticotroph tumors are grouped as densely or sparsely
granulated according to Periodic Acid-Schiff (PAS) and
ACTH immunoreactivity characteristics 3,6-9. It has
been reported that densely granulated corticotroph tumors
(DGCT) were detected in smaller adenomas with a calmer
clinical course, whereas sparsely granulated corticotroph
tumors (SGCT) were detected in larger, more aggressive
and invasive tumors 3,6-8. Furthermore, Crooke’s cell
tumors constitute another subtype, which is relatively rare
and is considered to be more aggressive than others 9,10.
Given the scarcity of the studies correlating clinical and
laboratory findings on the tumor granulation pattern
in CD, we aimed to investigate the clinicopathological
characteristics of DGCTs and SGCTs in this study.
Among a total of 320 patients, who were diagnosed with
functional pituitary tumor and followed-up at the Istanbul
Medical Faculty pituitary out-patient clinic, 54 patients
(17%) were diagnosed with CD. Patients with an accurate
histological re-evaluation of tumor subtype analysis were
included in this study (n=41). The diagnosis of CD was
based on the clinical and radiological findings (pituitary
tumor by sellar magnetic resonance imaging-MRI) and
laboratory tests. The laboratory diagnosis of CD was
confirmed by failure to suppress plasma cortisol levels
(>1.8 μg/dl) after administration of 1 mg-overnight and
low dose dexamethasone suppression tests (48 hours, 2
mg/day), high ACTH levels and suppressed cortisol levels
with the high dose dexamethasone test (>50% suppression
from baseline serum cortisol levels) in accordance with the
current guideline 1
The surgical method performed on all patients was
transsphenoidal surgery (TSS). The patients with ACTH
positive immunostaining adenoma were enrolled in the
study, whereas the patients with a pathology result of
hyperplasia or normal pituitary tissue or ACTH-negative
staining were excluded from the study. All pathological
specimens were re-evaluated by an experienced pathologist
(BB). Initial evaluation was performed by hematoxylineosin
and subsequently silver stain; those with a preserved
acinar reticular pattern were excluded as expected with
normal pituitary tissue or hyperplasia. The PAS stain was
used to identify corticotroph cells. Diffuse and strong
staining by PAS and ACTH were identified as DGCT,
whereas faint staining by PAS and focal, weak staining by
ACTH were identified as SGCT 3,6-10. Typical abundant
perinuclear ring-like patterns with low molecular weight
keratin (LMWK) were identified as Crooke’s cell tumors
3,6-10. Examples of granulation pattern and MRI from
the patient cohort are shown in Figure 1A-F;2A,B.
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|Figure 1: Histological, histochemical and immunohistochemical features of corticotroph tumors. A) Microscopic view of pituitary
adenoma (H&E; x200). B) Densely granulated corticotroph tumor dominated by the tumor cells with diffuse and strong PAS staining
(PAS; x100) C) Sparsely granulated corticotroph tumor dominated by the tumor cells with focal and weak PAS staining (PAS; x200).
D) Densely granulated corticotroph tumor dominated by the tumor cells with diffuse and strong ACTH staining (IHC; x200). E) Sparsely
granulated corticotroph tumor dominated by the tumor cells with focal and weak ACTH staining (IHC; x200). F) Crooke’s hyaline
changes with cytokeratin staining as ring-like pattern on corticotroph cells (IHC; x400).
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|Figure 2: Magnetic resonance imaging features of corticotroph tumors. A) T1 and T2 weighted sequence images of a corticotroph
microadenoma; 6x9 mm microadenoma involving the left side of the pituitary gland (white arrow). B) T1 and T2 weighted sequence
images of a corticotroph macroadenoma; 22x16 mm macroadenoma involving the pituitary gland (white arrow).
DGCTs and SGCTs were compared in terms of age, sex,
maximum tumor diameter, estimated duration of CD
(calculated according to the information in the patient’s
history), baseline cortisol, ACTH levels and Ki-67 labeling
index. Crooke’s cell tumors were excluded from evaluation
due to the low number of patients available for these
comparisons. The Ki-67 labeling index was evaluated
through MIB1 antibody in the tumor tissue samples.
The Ki-67 labeling index was assessed by the eye-balling
method and when the index was over 1-2%, approximately
100 nuclei of the tumor cells at x400 magnification were
counted in the evaluation of the Ki-67 score.
Remission rates and persistent hypercortisolism after TSS
were compared between the groups. A plasma cortisol
level of < 2 μg/dL in the first week after TSS and no
recurrence during the follow-up period were determined
as remission with TSS and these were compared with the
hypothalamic-pituitary-adrenal (HPA) axis recovery time.
HPA axis recovery was evaluated by morning cortisol and/
or ACTH stimulation tests. Prednisolone replacement was
discontinued when morning plasma cortisol levels were
≥10 μg/dL or stimulated cortisol levels were approximately
≥18 μg/dL with the ACTH stimulation test (2). A plasma
cortisol level >2 μg/dL on the first week after TSS was
determined as persistent hypercortisolism and recurrence
was defined in patients who developed clinical and
laboratory signs of hypercortisolemia during the follow-up
period 2,11. At least one of the options of repeat surgery,
medical treatment, radiotherapy (RT) and bilateral
adrenalectomy was applied during the follow-up period for
persistent disease or recurrence, and the remission rates at
the last visit were compared under these treatments.
The majority of the patients (71%) had DGCTs (n=29);
whereas 24% of the patients had SGCTs (n=10) and 5%
of the patients had Crooke’s cell tumors (n=2). DGCTs
and SGCTs groups were similar in terms of age, sex,
baseline cortisol and ACTH levels, whereas SGCTs were
larger and the numbers of macroadenomas at borderline
were higher than DGCTs (p=0.034, p=0.05, respectively).
Estimated duration of CD was longer in SGCTs; however,
the difference was not statistically significant.
Rates of remission with TSS were similar between the groups
whereas HPA axis recovery time was longer in SGCTs
(p=0.033); however, rates of permanent hypocortisolism
without adrenalectomy were similar. Persistent disease
after TSS was slightly higher in DGCTs and recurrences
were frequent in SGCTs; however, the differences were not
statistically significant. The remission rates at the last visit
were similar in the groups with similar mean follow-up
periods and the Ki-67 labeling indexes of the tumors were
also similar. Detailed data about comparison of DGCTs
and SGCTs are shown in Table I.
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|Table I: Distribution of clinical, laboratory data and treatment responses in corticotroph adenomas according to the granulation pattern.
In our series, the majority of corticotroph tumors were
DGCT. It is reported in the literature that the majority of
corticotroph tumors were densely granulated 3,6-8,10,12
However, in a recent study, Mete et al. 13
frequency of SGCTs and DGCTs in their cohort as 29%
and 47%, respectively and interpreted this result as an interesting finding. However, they explained these findings
with the relatively high frequency of Crooke’s cell tumors
(13% of corticotroph tumors), the identification of mixed
densely and sparsely granulated corticotroph tumors in
some patients, and the role of p27 immunohistochemistry
in the prediction of corticotroph tumor functionality 13
In our study, we focused on the association between
granulation pattern of corticotroph tumors and the
baseline findings of the disease. Accordingly, the groups
were similar in terms of sex distribution and, as expected,
female dominance existed in both groups. Although
age at diagnosis was slightly increased in the SGCTs, the difference was not significant and this result was
similar to a recent study 13. Early diagnosis of CD has
effectively reduced the mortality rates and prevented the
severe comorbidities observed in these patients 14,15.
For this reason, we evaluated the duration until diagnosis
of CD based on the patient information and findings; and
compared the groups to assess the association between
granulation pattern and indolent disease period. According
to this, while this duration was slightly longer in SGCTs,
the difference was not statistically significant, and if patient
numbers were increased, more meaningful results could be
obtained. We concluded that the CD findings are slower
and insidious in SGCTs. A negative correlation between the tumor diameter and symptomatology in corticotroph
tumors have been well adapted with a view of CD as
“small tumor, big Cushing; big tumor, small Cushing” 8.
Similarly, tumor sizes were larger in SGCTs in our patients;
and as expected macroadenomas were more frequent in
this group. It was reported that SGCTs were larger, invasive
tumors and small microadenomas are frequently densely
granulated 3,6-8. Despite larger tumor size in SGCTs,
baseline ACTH and cortisol levels were similar between
the groups; however, the similarity could be due to the low
number of patients in the groups.
Treatment goals in CD are to normalize cortisol secretion,
to prevent hypercortisolemia associated morbidities and
complications; and to provide a long-term remission
without recurrence 16. Since it is not always possible
to achieve and maintain these goals, we aimed to assess
the effect of the granulation pattern in achieving these
treatment goals. Remission with TSS and rates of persistent
disease after surgery were similar in these patients who were
treated with primary surgery. Normally, maximum tumor
diameter in SGCTs was larger; therefore, lower remission
or higher persistent disease rates could be expected in
SGCTs, and due to the presence of more microadenomas in
DGCTs, higher remission rates could be expected in these
patients. The reason for the similar frequencies is possibly
due to the insufficient detection of small microadenomas
by the surgeon as one of the most important predictors of
surgical outcomes in CD is pre-operative visualization of
pituitary tumors 16,17. Furthermore, although SGCTs
have more macroadenomas, the mean tumor size was
about 1 centimeter. It has been explained that remission
rates were lower in the tumors over 2 centimeters 18.
HPA axis recovery time was longer in SGCTs after the
surgery; however, post-operative frequencies of permanent
hypocortisolism were similar.
In addition to persistent hypercortisolism, recurrences may
occur during follow-up in patients with initial remission
after surgery, and a large-scale review has determined
the mean recurrence frequency as 13%. 16. As we have
already mentioned, it has been stated that recurrences or
Nelson’s syndrome is more frequent in SGCTs despite the
fact that there is no study comparing the rates of recurrence
3,6-9. In our study, recurrence rates were determined as
2-fold higher in SGCTs within similar follow-up durations
(14% and 30%), but the difference was not statistically
significant. Thus, we considered that these results may
be related to the small size of the study groups. We think
that the subtype of corticotroph tumors is important in predicting the recurrence, and closer monitoring is
therefore required. Presence of Crooke’s hyaline changes
in adjacent non-tumoral tissue confirms the presence of
hypercortisolemia and the presence or absence of Crook’s
hyaline changes with complete or incomplete pattern
properties, which may also be used in predicting remission
8,19. However, as the specimens did not contain adequate
adjacent adenohypophysis tissue, the presence or absence
of Crooke’s cell changes in the non-tumoral corticotrophs
could not be evaluated in this study. Further studies
with larger pathological specimens may be helpful in the
evaluation of the relationship between Crooke’s hyaline
changes and tumor granulation patterns. The absence
of this finding may indicate a more severe defect in the
feedback regulation of corticotrophs, which may be related
with an increased rate of recurrence 8,19.
It was demonstrated in somatotroph tumors that the
granulation pattern of the tumor is crucial in determining
the response to somatostatin analog therapy 20. However,
such data does not exist for corticotroph tumors in the
literature. In our study, there were not enough patients
receiving pituitary directed medical treatment such as
pasireotide or cabergoline in a long-term period, and
such an evaluation could therefore not be performed. We
believe that the present study would guide future studies in
prediction of a granulation pattern in response to medical
therapy, especially as the use of pasireotide will become
It was previously reported that SGCTs are more invasive
and aggressive. Some indexes such as Ki-67, p53, an loss of
p27 are used for behavioral detection of pituitary tumors
12,13,21,22. We assessed the Ki-67 labeling index in
corticotroph tumors with sufficient samples only. Despite
slightly higher averages of Ki-67 in SGCTs, the difference
was not statistically significant; and similar results were
shown in the study reported by Witek et al. 12. However,
the eye-balling method we used to evaluate Ki-67 is no
longer accepted in the field of neuroendocrine neoplasms
including those of pituitary origin and also a minimum of
500 tumor cells should be counted for this examination.
This is a deficit of our study, and it may be the reason why
the results were not statistically significant.
In conclusion, DGCTs are common in CD. DGCTs have a
small microadenoma pattern in comparison to SGCTs, the
indolent period is slightly longer, and post-operative HPA
axis recovery requires more time. Recurrences are slightly
more common in SGCTs; however, further studies with
larger series are needed to obtain more significant results.
The authors highly appreciate the efforts of Assistant
Professor Feyza Nur Tuncer (Istanbul University Aziz
Sancar Institute of Experimental Medicine, Department of
Genetics) in the language editing of this paper.
CONFLICT of INTEREST
The authors declare that they have no conflict of interest.
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