Whorls of Intermediate Filaments With Entrapped Neurosecretory Granules Correspond to the “Rhabdoid” Inclusions Seen in Pancreatic Endocrine Neoplasms

HER-2-positive primary neuroendocrine neoplasms of the breast with signet ring feature: A case report and review of literature

Background

Primary neuroendocrine neoplasm of the breast (BNEN) is an uncommon breast neoplasm, and in most cases, it presents as hormone receptors positive and HER-2 negative. Moreover, in neuroendocrine neoplasms (NENs), the signet ring feature is a rare morphological subtype, and only a few cases have been reported. Here, we report the case of a primary breast neuroendocrine neoplasm with an unusual signet ring cell appearance in this paper. The documentation of this case, combined with a review of the literature, may add to existing knowledge about the outcome and management of this rare tumor.

Methods

In the present review, we describe a unique case of HER-2-positive primary BNEN with a signet ring feature that has not been reported in English. Additionally, we performed a literature search of the PubMed and Web of Science databases and calculated statistics for clinical data and follow-up.

Results

Our literature search, excluding non-English literature, identified 15 articles with data from 24 cases, including ours. The mean age was 51.25 years (range, 30-79 years), and there were 13 male patients (54%) and 11 female patients (46%). Of the 24 cases, some cases (11/24) were associated with lymph node metastases, a few cases (6/24) had distant metastasis, and the vast majority of cases (23/24) occurred in the digestive system. Primary hepatic signet ring cell neuroendocrine tumor showed slow progression and good prognosis. Lymph node involvement was identified in one of eight (12.5%) documented cases, and one of eight (12.5%) reported cases presented with distant metastatic disease. However, the prognosis of neuroendocrine tumors with signet ring cells in the pancreas and stomach was poor. Lymph node involvement was identified in 9 of 15 (60%) documented cases, and 5 of 15 (33.3%) reported cases presented with distant metastatic disease.

Conclusion

NENs with a signet ring feature is uncommon, and this is the first case report of its occurrence in the breast. Current knowledge is limited to anecdotal experience based on case reports and small case series. We provide a literature review to summarize knowledge about this rare entity.

Morphologic Variants of Pancreatic Neuroendocrine Tumors: Clinicopathologic Analysis and Prognostic Stratification

Better prognostication/stratification of pancreatic neuroendocrine tumors (PanNETs) is needed. In this detailed morpheomic study of 163 resected PanNETs, 11 unusual variants, some of which were not previously recognized, and others scarcely documented in the literature, were identified, and their pathologic characteristics were further analyzed. By behavior and clinicopathologic associations, these variants could be grouped into three prognostically different categories. I. More aggressive (20%). Included in this group were the variants that in average showed higher grade and stage and adverse outcome including oncocytic, plasmacytoid, lipid-rich and previously unrecognized hepatoid variants, which often had a more diffuse/broad-band growth pattern, with some also displaying discohesiveness. They were characterized by abundant cytoplasm and often had prominent nucleoli (as seen in metabolically active cells), thus the provisional name "metabolic cell phenotype." Because of their diversion from classical neuroendocrine cytomorphology, these variants created challenges on original diagnostic workup, particularly hepatoid examples, which revealed Arginase 1/Hep Par-1 expression in 50%. II. Less aggressive (10%). These cases either showed signs of maturation, including nested growth, paraganglioid pattern (which was previously unrecognized), and organoid PanNETs such as "ductulo-insular" growth, or showed symplastic/degenerative changes, and despite their paradoxically disconcerting histology, were more benevolent in behavior. III. Undetermined. There were other variants including mammary tubulolobular-like, pseudoglandular, peliotic, and sclerotic PanNETs, which although diagnostically challenging, their biologic significance could not be determined because of rarity or heterogeneous characteristics. Prognostic associations: Features that were significantly different in the more aggressive group than the less aggressive group were median size (5.0 vs 1.6 cm, p < 0.001), percentage of pT3+T4 cases (72% vs 12%, p < 0.001), Ki67 index (5.3% vs 2.3%, p = 0.001), % G2 and G3 cases (77% vs 27%, p < 0.001), and rate of lymph node and distant metastasis (96% vs 27%, p < 0.001). In stepwise logistic regression model using the 3 established prognosticators of T stage, size, and grade along with morphology, only aggressive-morphology (metabolic cell phenotype) was found to be associated with metastatic behavior with an odds ratio of 5.9 with 95% confidence interval (C.I.) 1.688 to 22.945 and p value 0.007. In conclusion, PanNETs display various morphologic patterns that are not only challenging and important diagnostically but appear to have biologic significance. Tumors with more diffuse growth of cells with nucleoli and abundant cytoplasm and/or discohesion (oncocytic, hepatoid, lipid-rich, plasmacytoid PanNETs), provisionally termed "metabolic cell phenotype," show aggressive characteristics and are an independent determinant of adverse outcome and thus may require closer post-surgical follow-up, whereas variants with more degenerative or mature features (ductuloinsular, pleomorphic, paraganglioma-like) appear to be more benevolent despite their more atypical and worrisome morphology.

Neuroendocrine tumor of the pancreas with rhabdoid feature

Imaging of a 53-year-old Japanese man revealed two tumors in the liver and a tumor in the head of the pancreas with a swelling lymph node. A needle biopsy for the liver tumors was performed, revealing a neuroendocrine tumor. Enucleation, lymphadenectomy, and partial hepatectomy were performed. The microscopic examination identified many tumor cells with intracytoplasmic inclusions arranged in a nested, cord, or tubular fashion. The intracytoplasmic inclusions displayed densely eosinophilic globules and displaced the nuclei toward the periphery, which constitutes “rhabdoid” features. The tumor cells were positive for synaptophysin and weakly positive for NCAM, but negative for chromogranin A. Epithelial markers (AE1/AE3 and CAM5.2) accentuated intracytoplasmic globules. Pancreatic neuroendocrine tumors with rhabdoid features are very rare. Generally, rhabdoid features are aggressive and dedifferentiated characteristics of various types of tumor. Pancreatic neuroendocrine tumors containing rhabdoid cells tend to display extrapancreatic spread at the time of presentation, although some of these tumors with rhabdoid features are not always associated with aggressive behavior.

Pathology diagnosis of pancreatic neuroendocrine tumors

Histopathology of pancreatic neuroendocrine tumors (PNETs) typically displays characteristic features. However, pathologists may encounter histological variants that may resemble other pancreatic tumors. Immunohistochemistry is a powerful tool in confirming neuroendocrine differentiation and differentiating PNETs with other pancreatic neoplasms. Histopathological features could be associated with inherited syndromes. Once the pathology diagnosis of neuroendocrine tumor was made, an accurate grading based on World Health Organization (WHO) classification is required. This review will focus on histology variants, immunohistochemistry and WHO classification of PNET.

Endocrine tumours of the pancreas

Verbeke C S (2010) Histopathology 56, 669-682 Endocrine tumours of the pancreas Histopathology reporting of pancreatic endocrine neoplasms is complex. The tumours can exhibit a variety of morphological appearances, which often require careful differential diagnostic consideration. Prediction of tumour behaviour and clinical outcome is based on the World Health Organization classification and TNM staging and grading system, which share some criteria and premises, but differ significantly in others. Clinicopathological correlation through discussion at multidisciplinary team meetings is of paramount importance. In this review special emphasis is given to the items of information that can and should be provided by the pathologist to allow optimal patient management. The review further discusses areas of current controversy and uncertainty, of which pathologists participating in multidisciplinary discussions should be aware.

Mucin-secreting gastric adenocarcinoma with Rhabdoid areas

Rhabdoid tumor, first described in kidneys of infants and children, is an aggressive tumor that has been reported in several extrarenal locations. In this report, we describe the case of a 40-year-old patient with gastric adenocarcinoma composed of histologically well-differentiated glandular areas and focal rhabdoid zones. The rhabdoid component showed typical features such as abundant eosinophilic cytoplasm, eccentric nuclei, prominent nucleoli and intense focal positive immunohistochemical cytoplasmic reaction for vimentin. Recognition of the rhabdoid phenotype in gastrointestinal tract neoplasms is important because this feature is associated with poor prognosis and unresponsiveness to conventional therapy.

Endocrine neoplasms of the pancreas: pathologic and genetic features

CONTEXT

Pancreatic endocrine neoplasms (PENs) are diagnostically challenging tumors whose natural history is largely unknown. Histopathology allows the distinction of 2 categories: poorly differentiated high-grade carcinomas and well-differentiated neoplasms. The latter include more than 90% of PENs whose clinical behavior varies from indolent to malignant and cannot be predicted by their morphology.

OBJECTIVES

To review the literature and report on additional primary material about the clinicopathologic features, classification, staging, grading, and genetic features of PENs.

DATA SOURCES

Literature review of relevant articles indexed in PubMed (US National Library of Medicine) and primary material from the authors' institution.

CONCLUSIONS

The diagnosis of PEN is generally easy, but unusual features may induce misdiagnosis. Immunohistochemistry solves the issue, provided that the possibility of a PEN has been considered. Morphology allows the distinction of poorly differentiated aggressive carcinomas from well-differentiated neoplasms. The World Health Organization classification criteria allow for the discernment of the latter into neoplasms and carcinomas with either benign or uncertain behavior. The recently proposed staging and grading systems hold great promise for permitting a stratification of carcinomas into clinically significant risk categories. To date, inactivation of the MEN1 gene remains the only ascertained genetic event involved in PEN genesis. It is inactivated in roughly one-third of PENs. The degree of genomic instability correlates with the aggressiveness of the neoplasm. Gene silencing by promoter methylation has been advocated, but a formal demonstration of the involvement of specific genes is still lacking. Expression profiling studies are furnishing valuable lists of mRNAs and noncoding RNAs that may advance further the research to discover novel markers and/or therapeutic targets.

Pleomorphic pancreatic endocrine neoplasms: a variant commonly confused with adenocarcinoma

Most pancreatic endocrine neoplasms (PENs) have distinctive endocrine growth patterns and uniform nuclear morphology; they are regarded as relatively low-grade tumors. Significant nuclear pleomorphism is a feature that may raise concerns about aggressive behavior or even obscure the endocrine nature of the neoplasm. Eight PENs exhibiting marked nuclear pleomorphism (>20% of the tumor cells) were identified during a review of 136 PENs (5.9%) from the pathology files of Memorial Sloan-Kettering Cancer Center. The histologic, immunohistochemical, ultrastructural (4 cases), and clinical features were reviewed. There were 6 males and 2 females ranging from 30 to 69 years (mean, 55 years). The tumors averaged 5.8 cm (range, 1.5-14 cm). Six tumors (75%) were initially misdiagnosed in 5 cases as adenocarcinoma and in one as solid-pseudopapillary tumor; in 2 cases, the misdiagnosis was based on fine needle aspiration cytology and in 4 on histologic examination. The architectural features of the tumors resembled those of other PENs, but the nuclei were markedly enlarged, irregularly shaped, and hyperchromatic, with frequent bizarre forms. Cells with pleomorphic nuclei also generally had abundant cytoplasm, sometimes with large perinuclear glassy inclusions. The mitotic rate was not elevated compared with other PENs, averaging 1.9 (range, 0-7) per 50 high power fields. Immunohistochemical findings were (number positive/number stained): chromogranin (8 of 8), synaptophysin (7 of 8), progesterone receptor (4 of 7), CD99 (2 of 5), S-100 protein (3 of 7), and p53 (0 of 6). Scattered cells expressed peptide hormones in a minority of cases. By electron microscopy, abundant dense core granules were identified, in some cases embedded within perinuclear arrays of intermediate filaments. Six patients underwent curative resection; at follow-up, 4 were free of disease at 11, 13, 30, 112 months (mean, 42 months), 1 developed liver metastases at 77 months and was alive with disease at 94 months, and 1 was lost to follow-up. Two patients had unresectable tumors and were alive with disease at 10 and 78 months. Striking nuclear pleomorphism may occur in otherwise typical PENs and commonly causes difficulties in the distinction from adenocarcinoma. There does not appear to be prognostic significance to these nuclear changes, and the morphologic features of pleomorphic PENs otherwise resemble those of their conventional counterparts.

Pancreatic endocrine tumour with cytoplasmic keratin whorls. Is the term "rhabdoid" appropriate?

A 50 year old woman presented with acute abdominal pain accompanied by nausea and vomiting and was found to have a mass in the head of the pancreas by imaging. The clinical impression was of a pancreatic carcinoma and a Whipple's procedure was performed. Microscopic examination of the tumour showed it to be a low grade neuroendocrine carcinoma arranged in a tubuloacinar or tubulopapillary pattern, and composed of cells harbouring very prominent intracytoplasmic inclusions. These inclusions varied in appearance from being pale pink and hyaline in quality to more eosinophilic and globular causing displacement of the nucleus. Ultrastructural examination showed typical paranuclear aggregates of intermediate filaments. Inclusions of this type have been described previously as "signet ring like" and "rhabdoid". It was felt that the inclusions more closely resemble the fibrous bodies that are seen in pituitary adenomas. In addition, it is suggested that both signet ring and rhabdoid are not appropriate because they do not reflect histogenesis and are not necessarily reflective of tumour biology. It is suggested that the term "cytokeratin aggresomes" should be used to describe this distinctive phenotype.