Pituitary Gland

• برای بزرگنمایی عکسها کلیک را روی ان نگه دارید.....

 Figure 44.1 Fetal pituitary gland at 12 weeks' intrauterine gestational age shows TTF1 immunoreactive nuclei already identifiable in the posterior gland (at left) but not in the anterior gland (at right)

Figure 44.2 Adult posterior pituitary gland with nuclear TTF1 immuno- reactivity; TTF1 IHC does not distinguish between normal posterior gland and TTF1 IHC(+) sellar region tumors, such as pituicytoma, spindle cell oncocytoma, and granular cell tumor of the neurohypophysis

 Figure 44.3 Fetal pituitary gland at 22 weeks' intrauterine gestation shows clear distinction between fibrillary posterior (upper right) and highly vascular epithelial anterior (lower left) portions of the gland

Figure 44.4 Fetal pituitary gland at 22 weeks' intrauterine gestation already shows immunoreactivity for anterior pituitary hormones, with growth hormone from the lateral wings illustrated here

 Figure 44.5 Sagittal magnetic resonance imaging (MRI) scan shows normal adult anterior and posterior pituitary and sellar region anatomy. The posterior pituitary "bright spot" is a normal MRI finding, referring to the intrinsically high T1 signal in the posterior pituitary attributed to the storage of vasopressin

 Figure 44.6 Diffuse immunoreactivity with PIT1 transcription factor identifies shared lineage in a large family of adenoma types: sparsely granulated prolactinomas, densely granulated prolactinomas, acidophil stem cell adenomas, densely granulated growth hormone adenomas, sparsely granulated growth hormone adenomas, mixed GH-PRL adeno- mas, thyrotroph adenomas, and plurihormonal PIT1-positive adenomas, formerly known as "silent type 3 adenomas."

 Figure 44.13 Incidental pituitary adenomas are a frequent finding not only on premortem neuroimaging studies but at the time of autopsy; this one was a prolactinoma

Figure 44.14 Pituitary adenomas more than 1 cm in greatest dimension are termed macroadenomas; compare with the sagittal MRI shown of normal gland in Fig. 44.5

Figure 44.15 Giant pituitary adenomas, defined as greater than 4 cm, sometimes extend into the nasopharyngeal space, mimicking a naso- pharyngeal carcinoma

Figure 44.30 Gonadotroph adenoma shows patchy LH IHC(+), but this is usually in a smaller subpopulation of the adenoma cells than is FSH IHC(+), or may not be present at all

 Figure 44.31 Hormone-negative adenomas often show a perivascular "pseudorosette" like pattern identical to that seen in gonadotroph adenomas

Figure 44.32 Hormone-negative adenomas may be composed of a very monomorphic population of cells, punctuated only by a few mucin-filled microcysts

Figure 44.33 Densely granulated growth hormone adenomas show perinuclear keratin that is present throughout the cytoplasm with CAM5.2 immunostaining

Figure 44.36 This mixed GH-PRL adenoma clearly shows two admixed populations of chromophobic and eosinophilic cells on H&E

 Figure 44.37 Mixed GH-PRL adenomas present with acromegaly, and a significant percentage of the adenoma cells stain with GH

Figure 44.38 Although mixed GH-PRL adenomas present with acro- megaly, they are often associated with hyperprolactinemia as well and as shown here contain a higher percentage of PRL+ cells than densely granulated GH adenomas, which should only contain occasional cells that are immunoreactive for PRL

Figure 44.39 Sparsely granulated prolactinomas constitute the overwhelm- ing majority of prolactinomas, and usually feature a sheet-like growth pattern; note the relative prominence of nucleoli (compare with Fig. 44.32)

Figure 44.40 Sparsely granulated prolactinomas show PRL positivity in an arc-like cytoplasmic pattern, the so-called Golgi pattern. In contrast, the very rare densely granulated PRL positive adenomas show PRL immunoreactivity throughout the cytoplasm

 Figure 44.41 Sparsely granulated prolactinomas occasionally show stromal hyalinization and microcalcifications, both of which are pictured here

Figure 44.42 Atypical adenomas are defined by an elevated MIB-1 labeling index, although this does not correlate perfectly with adenoma subtype. Indeed, even the well-accepted "aggressive" adenoma subtypes, such as sparsely granulated GH, acidophil stem cell, and silent ACTH adenoma, do not invariably show elevated indices. In some studies, the most common subtype to show elevated MIB-1 is sparsely granulated prolactinoma, as illustrated here. Acidophil stem cell adenoma was excluded in this case by clinical and EM features

Figure 44.43 Acidophil stem cell adenoma usually presents as a large tumor, with relatively mild hyperprolactinemia for tumor size in comparison to sparsely granulated prolactinomas. Acidophil stem cell adenomas cannot be confidently diagnosed without electron microscopic examination, however. One clue in some cases is the presence of large clear vacuoles corresponding to the giant mitochondria seen on EM

Figure 44.46 Densely granulated corticotroph adenomas show diffuse ACTH immunoreactivity throughout the tumor. Unlike sparsely granulated prolactinomas where adenoma size parallels the serum level of prolactin, minute ACTH adenomas, even millimeters in size, may cause Cushing disease and significantly elevated serum levels

Figure 44.47 Sparsely granulated corticotroph adenomas are usually chromophobic

Figure 44.48 Sparsely granulated corticotroph adenomas show focal or patchy ACTH positivity

Figure 44.49 Crooke cells in adjacent nontumorous anterior pituitary gland testify to the presence of hypercortisolism, and this change should be sought in any included anterior gland from a corticotroph adenoma resection specimen. Rings of keratin push the ACTH-positive granules close to the nucleus, as well as to submembrane sites

Figure 44.50 Pituitary apoplexy can be seen in several types of adenomas, usually macroadenomas, and may either manifest as bland necrosis, as illustrated here in an adenoma that was present within clival bone, or as acute/subacute hemorrhage

Figure 44.51 Rathke cleft cyst contains variably dense colloid-like proteinaceous contents, usually visible as amorphous eosinophilic material (left). The lining epithelium is often not sent to the pathologist, but, when received, may be columnar ciliated epithelium (as seen here), low cuboidal, or even show squamous metaplasia

Figure 44.52 Adamantinomatous craniopharyngioma is characterized by peripherally palisaded nuclei, clusters of eosinophilic cells devoid of nuclear staining, so-called ghost cells (also known as wet keratin), focal calcification, and often, surrounding piloid gliosis with Rosenthal fiber formation (upper right and at left)

Figure 44.53 Adamantinomatous craniopharyngioma has an underlying mutation in B-catenin and translocation of the protein to the nucleus, which can thus be documented by immunohistochemistry. It should be noted that nuclear ẞ-catenin staining is never seen in all tumor cells, but instead concentrates in cells immediately adjacent to wet keratin or within whorled squamous nests (seen in the plane of section at lower right)

Figure 44.54 Papillary craniopharyngioma lacks the prominent peripheral palisaded nuclei, wet keratin, and calcification of the adamantinomatous variety; note the hyalinized, collagenous whorl-like structures that should not be mistaken for wet keratin

Figure 44.55 Papillary, squamous craniopharyngiomas are composed of benign nonkeratinizing epithelium devoid of a keratohyaline layer, unlike epidermoid cysts. Unlike adamantinomatous craniopharyngioma, papillary craniopharyngioma manifests mutation in BRAF V600E, which is paralleled by BRAF VE1 immunoreactivity, as shown here with a red chromogen

Figure 44.56 Pituicytoma is a spindle cell sellar region mass easily mistaken on light microscopy for meningioma, schwannoma, or even normal posterior pituitary gland

Figure 44.57 Pituicytoma, like the related spindle cell oncocytoma and granular cell tumor of infundibulum, shows nuclear reactivity for TTF1, negating consideration of meningioma, schwannoma, or even pituitary adenoma. The cell density and architectural pattern distinguishes it from TTF1+ normal posterior gland

Figure 44.58 Spindle cell oncocytoma is composed of cells with plumper, more epithelioid-appearing eosinophilic cytoplasm but does have overlapping features with pituicytoma, most notably the shared TTF1 immunoreactivity

Figure 44.59 Spindle cell oncocytoma is characterized by more abundant cytoplasmic mitochondria than are present in pituicytoma, as seen here on anti-mitochondrial immunohistochemistry

Figure 44.62 In this case the metastatic breast carcinoma shows strong diffuse nuclear immunoreactivity for estrogen receptor. Note, however, that the residual normal anterior pituitary gland, at lower right, also contains a few scattered, smaller-sized nuclei that are also ER positive. These are either gonadotrophs or lactotrophs