Studies on intranuclear inclusions and nuclear grooves in papillary thyroid cancer by light, scanning electron and transmission electron microscopy

Diagnostic Utility of p62 Expression in Intranuclear Inclusions in Thyroid Core Needle Biopsy Specimens

BACKGROUND/AIM

Core needle biopsy (CNB) has been widely used as an alternative method to ultrasound-guided fine-needle aspiration cytology for histological diagnosis of thyroid specimens. However, nuclear artifactual vacuoles (NuVas) produced during tissue processing can be very difficult and sometimes impossible to distinguish from intranuclear inclusions (NuIns). P62 is an autophagy receptor that recognizes, targets, and eliminates toxic cellular materials during autophagy. Herein, we examined the utility of p62 immunohistochemical staining to detect NuIns in thyroid core needle biopsy specimens.

PATIENTS AND METHODS

Thirty-five thyroid CNB slides from 32 patients and corresponding resection specimens stained with hematoxylin and eosin were reviewed by two pathologists. The immunohistochemical staining pattern of p62 was used to differentiate NuIns from NuVas. The diameter of each nucleus (A) and NuIn (B) was measured, and the number of p62-expressing NuIn-positive (p62In) cells was counted using 1/2 (B/A) and 1/3 (B/A) criteria. The criterion of 1/3 includes NuIns larger than 1/3 and smaller than 1/2 of the nuclear diameter. The criteria of 1/2 includes NuIns larger than 1/2 of the nuclear diameter.

RESULTS

By applying the 1/2 criterion, there were no p62In cells in follicular adenoma (FA) samples. However, in papillary thyroid carcinoma (PTC) samples, 22 of 25 specimens exhibited p62In cells. The sensitivity and specificity to distinguish FA from PTC using the 1/2 criterion were 0.88 and 1.00, respectively. By applying the 1/3 criterion, there was one p62In cell hit in FA samples. However, 23 of 25 PTC specimens showed p62In cells. The sensitivity and specificity to distinguish FA from PTC using the 1/3 criterion were 1.00 and 0.90, respectively.

CONCLUSION

P62 is a useful marker for distinguishing FA and PTC based on CNB specimens. We suggest the 1/2 criteria for identifying p62In cells.

New insights into intranuclear inclusions in thyroid carcinoma: Association with autophagy and with BRAFV600E mutation

Background

Intranuclear inclusions (NI) in normal and neoplastic tissues have been known for years, representing one of the diagnostic criteria for papillary thyroid carcinoma (PTC). BRAF activation is involved among others in autophagy. NI in hepatocellular carcinoma contain autophagy-associated proteins. Our aim was to clarify if NI in thyroid carcinoma (TC) have a biological function.

Methods

NI in 107 paraffin-embedded specimens of TC including all major subtypes were analyzed. We considered an inclusion as positive if it was delimited by a lamin AC (nuclear membrane marker) stained intact membrane and completely closed. Transmission electron microscopy (TEM), immunohistochemistry (IHC), immunofluorescence (IF) and 3D reconstruction were performed to investigate content and shape of NI; BRAF^V600E mutation was analyzed by next generation sequencing.

Results

In 29% of the TCs at least one lamin AC positive intranuclear inclusion was detected; most frequently (76%) in PTCs. TEM analyses revealed degenerated organelles and heterolysosomes within such NI; 3D reconstruction of IF stained nuclei confirmed complete closure by the nuclear membrane without any contact to the cytoplasm. NI were positively stained for the autophagy-associated proteins LC3B, ubiquitin, cathepsin D, p62/sequestosome1 and cathepsin B in 14–29% of the cases. Double-IF revealed co-localization of LC3B & ubiquitin, p62 & ubiquitin and LC3B & p62 in the same NI. BRAF^V600E mutation, exclusively detected in PTCs, was significantly associated with the number of NI/PTC (p = 0.042) and with immunoreactivity for autophagy-associated proteins in the NI (p≤0.035). BRAF-IHC revealed that some of these BRAF-positive thyrocytes contained mutant BRAF in their NI co-localized with autophagy-associated proteins.

Conclusions

NI are completely delimited by nuclear membrane in TC. The presence of autophagy-associated proteins within the NI together with degenerated organelles and lysosomal proteases suggests their involvement in autophagy and proteolysis. Whether and how BRAF^V600E protein is degraded in NI needs further investigation.

Papillary Thyroid Carcinoma and Related Thyroid Neoplastic Lesions: A Light Microscopic Study with Emphasis on Nuclear Changes

A total of 187 thyroid lesions consisting of 2 cases of Grave's disease, 21 cases of multinodular goiter, 40 follicular adenomas and 124 low-grade papillary thyroid carcinomas were studied to identify intermediate neoplastic lesions in the spectrum of nuclear changes between benign reactive thyroid follicles and low-grade thyroid papillary carcinoma. The lesions were examined and classified on the basis of the following nuclear features: fine chromatin seen in the thyroid papillary carcinomas and coarse chromatin seen in follicular carcinomas. Cases with Hürthle cell changes were excluded from the study. Cases with nuclei containing coarse chromatin were classified in the group of follicular adenomas with a coarse chromatin pattern. The neoplastic thyroid lesions containing fine chromatin showed a spectrum of nuclear changes ranging between reactive follicular lesions and papillary thyroid carcinoma with lymph node metastasis. Such lesions were classified as follicular adenomas with a fine chromatin pattern. The nuclei of these lesions were graded into mild to marked "nuclear atypia with a fine chromatin pattern". The degree of atypia depended on the degree and extent of nuclear changes. Encapsulated follicular adenomas with a fine chromatin pattern and with mild atypia (11 cases), moderate atypia (13 cases), marked atypia (27 cases), and encapsulated or nonencapsulated papillary thyroid carcinoma were characterized by uniform nuclei; with mild, moderate and marked nuclear atypia in less than 2/3 of the cell population and marked nuclear atypia in more than 2/3 of the cell population; and measuring 5.4-6.3, 6.0-7.2, 6.3-9 and 7.2-10 microns in diameter, respectively. Follow-up of cases of papillary thyroid carcinoma fulfilling the above criteria showed lymph node metastasis in 33% of cases, whereas follicular adenomas with a fine chromatin pattern, including cases originally diagnosed as papillary carcinoma, showed no evidence of lymph node or distant metastasis in a follow-up period of 30 months to 15 years. In the thyroid tissue surrounding papillary thyroid carcinoma or encapsulated follicular adenoma with a fine chromatin pattern and marked atypia, adenomatous nodules with a fine chromatin pattern and with low-grade nuclear atypia were identified. The adenomatous nodules with a fine chromatin pattern and with mild, moderate and marked atypia showed architectural, cytoplasmic and nuclear features similar to those of follicular adenoma with a fine chromatin pattern of the same grade. Of interest, a large number of cases of follicular adenoma with a fine chromatin pattern had areas with features of follicular adenoma with a coarse chromatin pattern.

Ubiquitin Immunostaining in Thyroid Neoplasms Marks True Intranuclear Cytoplasmic Pseudoinclusions and May Help Differentiate Papillary Carcinoma from NIFTP

Papillary thyroid carcinoma (PTC) is defined by an invasive growth pattern and classic nuclear features: enlarged, grooved, overlapping nuclei with chromatin clearing and intranuclear cytoplasmic pseudoinclusions (INCP). True INCPs are characteristic of PTC, but may infrequently be seen in noninvasive follicular thyroid neoplasms with papillary-like nuclear features (NIFTP). Nuclear abnormalities that mimic INCP ("pseudo-pseudoinclusions") are common in a variety of thyroid lesions. H&E and ubiquitin-stained whole tissue sections of classic PTC (n = 25) and NIFTP (n = 35) were evaluated. On H&E, true INCPs were present in all (100%) PTCs and absent in all NIFTPs (0%). Pseudo-pseudoinclusions were present in 13 (37%) NIFTPs. In 24 (96%) PTCs, ubiquitin was strongly expressed within INCPs. In NIFTPs, optically clear nuclei or pseudo-pseudoinclusions did not express ubiquitin (0/35). Occasionally, nuclear vacuoles in NIFTP demonstrated a marginated staining pattern, in which strong ubiquitin expression was seen at the periphery of the nucleus, but the central pale area was negative. In addition, 2 NIFTPs demonstrated intrafollicular psammomatoid calcifications which were strongly ubiquitin-positive. Psammoma bodies in PTC were ubiquitin-negative in the majority of cases. We report a previously undescribed finding: strong ubiquitin expression in true INCPs in PTC, absence of true INCPs in NIFTP, and absence of ubiquitin expression in pseudo-pseudoinclusions in NIFTP. This finding supports the difference between true INCPs (found only in PTC) and pseudo-pseudoinclusions (found in NIFTP). Using strict histologic criteria and ubiquitin immunostaining, the presence of true pseudoinclusions may exclude a diagnosis of NIFTP. Caution should be exercised when interpreting nuclear vacuoles or pseudo-pseudoinclusions.

A case report of feline pituitary carcinoma with hypercortisolism

Feline pituitary tumors are rare. An 8-year-old male Japanese domestic cat presented with anorexia and emaciation. The cat died 17 days after admission from progressive neurological symptoms. At necropsy, a pituitary tumor measuring 25 × 18 × 15 mm was found. Microscopically, the tumor was divided into multiple lobules and had grown invasively into the adjacent brain tissue and sphenoid bone. Tumor cells had pleomorphic nuclei with prominent centrally located nucleoli and abundant amphophilic polygonal cytoplasm. Immunohistochemically, the tumor cells stained with anti-adrenocorticotropic hormone (ACTH), α-melanin-stimulating hormone (MSH) and β-endorphin antibodies. Ultrastructurally, the cytoplasm of the tumor cells contained various sized secretory granules. Based on these pathological findings, this tumor was diagnosed as pituitary carcinoma originated from pars intermedia cells.

Benign Hürthle cell adenoma with papillary architecture: a benign lesion mimicking oncocytic papillary carcinoma

We studied the significance of encapsulated Hürthle cell thyroid nodules with papillary structures lacking the nuclear features of papillary thyroid carcinoma (PTC); 19 cases fulfilling these criteria were encountered The patients' ages ranged from 22 to 40 years (32+/-6), and the F:M ratio was 3:1 The tumors measured from 0.5-5 cm (2+/-1.1). The diameter of the tumor cell nuclei ranged from 5.6 to 7.2 microns. Many nodules had nuclei displaying a fine chromatin pattern somewhat resembling those of PTC, but these were present in <20% of the tumor cells. Immunohistochemically, there was reactivity for MIB-1 in the papillary structures, negativity to focally weak reactivity for HBME and galectin-3, and negativity to moderate diffuse reactivity for CK19. Clinical follow-up from 1 to 19 years revealed no evidence of metastases in any of the cases. It is unlikely that the papillary structures in the study cases represent degenerative changes in view of the proliferative activity we have demonstrated in them. In view of (1) the encapsulation and the uniformity of the constituent cells, (2) the negative or weak immunoreactivity for galectin-3 and HBME and negative to moderate immunoreactivity for CK19, and (3) the absence or paucity of nuclear criteria for the diagnosis of PTC and the absence of lymph node metastasis in all study cases, we believe that these lesions represent the papillary variant of oncocytic follicular adenoma (Hürthle cell adenoma). Recognition of this entity is important to avoid an overdiagnosis of oncocytic PTC.

Etiology and significance of the optically clear nucleus

Papillary thyroid carcinoma (PTC) is diagnosed in both cytology and surgical pathology specimens on the basis of distinct nuclear morphology, characterized by nuclear elongation, chromatin clearing, intranuclear grooves, and inclusions. Although these nuclear features are specific to papillary carcinoma, they can be mimicked in some benign conditions. The majority of PTC cases do not pose diagnostic problems. However, a distinct subset of cases has generated controversy among experts. These cases are follicular patterned tumors that show minimal nuclear changes in PTC. Several investigators have explored the role of immunohistochemical markers in the histologic diagnosis of PTC. Somatic rearrangements of the RET protooncogene are the most frequent genetic abnormality found in PTC. The frequency of these rearrangements has varied according to the geographic region, radiation exposure, and methodologies used and histologic variant of PTC. Recent studies have suggested that RET/PTC may be the cause of this specific nuclear change in PTC; however, the role of RET/PTC in tumor progression still needs to be defined.

Follicular adenoma with papillary architecture: a lesion mimicking papillary thyroid carcinoma

AIMS

The purpose of this study was to investigate the significance of 'benign' encapsulated follicular thyroid nodules with papillary structures.

METHODS AND RESULTS

Twenty-one cases of encapsulated neoplastic thyroid nodules with papillary structures and nuclear features not diagnostic of papillary thyroid carcinoma (PTC) were obtained. All cases were reviewed with particular attention to nuclear features (fine chromatin pattern, optical clearing, grooves and inclusions). Representative sections were submitted for measurement of the maximum diameter of 200 round or nearly round nuclei and for immunostaining for MIB1, CK19, HBME and Ret oncogene protein. Nine cases displayed scattered optically clear nuclei or nuclear grooves in less than 30% of total neoplastic cells. They were grouped in the category of thyroid nodules with limited nuclear features of papillary thyroid carcinoma (PTC), but not diagnostic of PTC. The other 12 cases had fine or coarse chromatin, but lacked other features of nuclei in PTC. The diameter of the nuclei ranged from 5.6 to 7.2 microm and were smaller than those of PTC (6.3-10.0 microm). Immunostaining revealed positive reactivity for MIB1 in the papillary structures. Immunostaining for CK19 and HBME varied from negative or focally weak to diffusely moderate reactivity. Ret oncogene protein immunostaining showed focal and weak reactivity in one case and was negative in other cases of the study. Clinical follow-up from 6 months to 15 years revealed no evidence of metastasis.

CONCLUSIONS

The papillary structures in the study cases are unlikely to represent degenerative changes due to their proliferative activity. In view of (i) the encapsulation and the uniformity of the constituent cells, (ii) the varying degrees of immunoreactivity for CK19 and HBME and negative immunoreactivity for Ret oncogene protein, and (iii) the absence or insufficiency of nuclear criteria for the diagnosis of PTC and the absence of lymph node metastasis in all study cases, we believe that these lesions represent the papillary variant of follicular adenoma. Recognition of this pathological entity is important to avoid an over-diagnosis of PTC.

Neoplastic non-papillary thyroid carcinoma lesions with a fine chromatin pattern

In papillary thyroid carcinoma (PTC) in cytological and surgical specimens, fine chromatin, nuclear grooves and nuclear pseudoinclusions are the hallmarks of diagnosis. We investigated the significance of these nuclear changes in neoplastic non-PTC lesions. Fine needle aspiration biopsies (FNAB) of thyroid lesions were reviewed with histologic correlation. Twenty-five low-grade PTC and 35 neoplastic non-PTC lesions with a fine chromatin pattern in cytology specimens were identified. These lesions were studied along with five multinodular goiters and five follicular adenomas with a coarse chromatin pattern. The neoplastic non-PTC lesions were selected from cases with a histopathologic diagnosis of follicular neoplasm (accompanied by cytopathologic examination) but lacking a coarse chromatin pattern. The nuclear changes were separated into three grades of nuclear atypia with a fine chromatin pattern, depending on the degree of nuclear enlargement and nuclear membrane thickening, or the presence of nuclear grooves or pseudoinclusions. Thyroid lesions with a higher grade of nuclear atypia with a fine chromatin pattern were associated with larger nuclei and more readily visible nucleoli. These lesions correlated histologically with PTC and follicular adenomas with a fine chromatin pattern. The latter could be divided into three grades: grade 1 lesions having a fine chromatin pattern similar to that of nuclei with open chromatin seen in areas of nodular goiter; grade 3 lesions having nuclear features closest to those of PTC; and grade 2 lesions showing intermediate changes. In conclusion, there is a spectrum of nuclear changes in neoplastic non-PTC lesions with a fine chromatin pattern. These lesions are often diagnosed as follicular adenomas in surgical pathology and pose cytopathologic diagnostic problems between nodular goiter, follicular adenoma and PTC. The significance of follicular adenomas with a fine chromatin pattern will be discussed.

Fine-needle aspiration diagnosis of the follicular variant of papillary carcinoma

BACKGROUND

The follicular variant of papillary carcinoma (FVPC) presents significant diagnostic difficulty using fine-needle aspiration (FNA). Diagnoses by FNA vary considerably and usually are categorized as follicular proliferations.

METHODS

Conventional Papanicolaou, Diff-Quik, and hematoxylin and eosin stained FNAs from 16 cases of histologically confirmed FVPC were examined retrospectively. Each case was evaluated with respect to easily recognizable architectural and cytologic features. These were defined, ranked, and recorded for side-by-side comparison and identification of statistical significance. Similar features in six follicular carcinomas, seven follicular adenomas, and six adenomatous multinodular goiters were evaluated and compared as well.

RESULTS

Eight of 16 FVPC cases (including 5 macrofollicular variants) previously were diagnosed on FNA as a follicular neoplasm or follicular lesion, 6 were diagnosed as a papillary carcinoma or FVPC, and the remaining 2 were diagnosed as atypical. The cellularity and amount of colloid varied considerably between cases. Monolayered, twisted epithelial sheets and microfollicles or macrofollicles were the predominant microarchitecture. Powdery chromatin and easily identifiable nuclear grooves were present in 15 cases (94%), and intranuclear cytoplasmic (INC) inclusions were present in 11 cases (69%). These three features proved to be statistically significant in distinguishing FVPC from the other follicular lesions. No case exhibited true papillary clusters or psammoma bodies. Cases of follicular adenoma, follicular carcinoma, and adenomatous goiter shared many of these features, but notably lacked INC inclusions and abundant nuclear grooves.

CONCLUSIONS

Nuclear features such as abundant grooves, powdery chromatin, and INC inclusions were statistically significant and present in combination in the majority of cases of FVPC compared with the other follicular proliferations examined.

Presence of nuclear grooves in endometrial cytology

Although the presence of nuclear grooving in papillary carcinomas of the thyroid has been well-described, so far the attention paid to similar structures in endometrial cell samples has been limited. In order to investigate the occurrence of nuclear grooves in endometrial specimens from patients with various pathologic conditions of the endometrium, we compared their appearance with papillary thyroid cancers. A total of 10 cases was studied (age range, 40-72 yr), all cases demonstrating nuclear grooves. In each case, 10 random high-power fields (HPFs) were investigated, and the numbers of fields in which nuclear grooving could be seen were recorded. Nuclear grooves were observed in 3-36 of each HPFs and were more often observed in atypical endometrial cells than in their normal-appearing counterparts; however, these nuclear alterations were thought to be nonspecific findings.

Malignant plasmacytoid myoepithelioma of the palate: histological observations compared to benign predominant plasmacytoid myoepithelial cells in pleomorphic adenoma of the palate

Predominant benign plasmacytoid myoepithelial cells in pleomorphic adenoma and malignant plasmacytoid myoepithelioma cells were investigated morphologically. The cells of both tumors were plasmacytoid in appearance and sheet-like. Immunohistochemically, they were positive for keratin, vimentin, and S-100 protein, and negative for alpha-smooth muscle actin. In the malignant cells, large nuclei with irregular nuclear membranes and distinct nucleoi and occasional intranuclear inclusions and nuclear grooves were seen. Ultrastructural findings showed that the benign cells were richer in intermediate filaments and had fewer mitochondria. The intranuclear inclusions and nuclear grooves of the malignant cells were caused by invagination of the irregular nuclear membranes. Taken in their entirety, the above light microscopical nuclear findings may be useful as an adjunct for distinguishing malignant from benign plasmacytoid neoplastic myoepithelial cells of the salivary gland.