Ultrastructural features of neuroendocrine differentiated carcinomas of the breast

Spectrum of Mucin-containing Lesions of the Breast: Multimodality Imaging Review with Pathologic Correlation

Mucin-containing lesions of the breast encompass a wide range of benign and malignant processes. The spectrum of histologic findings includes incidental mucus-filled benign cysts or ducts, mucocele-like lesions (MLLs), mucin-producing ductal carcinoma in situ, and invasive mucinous carcinoma. MLL is characterized by the presence of mucin-containing cysts that are typically associated with extravasated stromal mucin. MLL is often benign but can be associated with epithelial atypia or malignancy. Mucinous carcinoma represents the malignant end of the spectrum of mucinous lesions of the breast. Evidence-based literature supports a conservative approach for benign MLLs without associated atypia or malignancy, reserving excision for those lesions exhibiting such pathologic features. The most common imaging finding for MLL is microcalcifications at mammography. No specific imaging feature is predictive of malignant outcome at surgical excision. Invasive mucinous carcinoma is a heterogeneous breast tumor subtype, as defined according to the World Health Organization criteria. Mucinous carcinomas are categorized into pure (>90% mucinous component) or mixed (10%-90% mucinous component) subtypes. Pure mucinous carcinomas are generally associated with excellent prognosis and survival, with a few exceptions. Mixed mucinous carcinomas do not have the same favorable prognosis and instead behave similarly to invasive breast carcinomas of no special type. Characteristic diagnostic imaging features can be identified for mucinous carcinoma based on its mucinous and nonmucinous contents. ©RSNA, 2023 Online supplemental material is available for this article. Quiz questions for this article are available through the Online Learning Center.

Classification of neuroendocrine neoplasms: lights and shadows

Neuroendocrine neoplasms (NENs) are a heterogeneous group of neoplastic proliferations showing different morphological features, immunophenotype, molecular background, clinical presentation, and outcome. They can virtually originate in every organ of the human body and their classification is not uniform among different sites. Indeed, as they have historically been classified according to the organ in which they primarily arise, the different nomenclature that has resulted have created some confusion among pathologists and clinicians. Although a uniform terminology to classify neuroendocrine neoplasms arising in different systems has recently been proposed by WHO/IARC, some issues remain unsolved or need to be clarified. In this review, we discuss the lights and shadows of the current WHO classifications used to define and characterize NENs of the pituitary gland, lung, breast and those of the head and neck region, and digestive and urogenital systems.

On the Endless Dilemma of Neuroendocrine Neoplasms of the Breast: a Journey Through Concepts and Entities

Neuroendocrine differentiation in breast carcinomas has been a matter of discussion since it was first described almost 60 years ago. Indeed, so-called neuroendocrine neoplasms of the breast (Br-NENs) are a less well-defined group of neoplasms than analogous entities in other anatomic sites, such as the lung and the gastroenteropancreatic (GEP) tract. Pure neuroendocrine phenotype is extremely rare, whereas the expression of neuroendocrine markers in usual breast carcinomas, both of special and of non-special type, without evident neuroendocrine morphology, is more common. In this context, the diagnostic criteria and the classification scheme for Br-NENs have been continuously changing over time and real consensus on this topic is still lacking, despite the recent publication of the 5th edition of the WHO classification of breast tumors. In this review, we will recapitulate the evolution of the concept of Br-NEN; revise the available knowledge on their morphological, molecular, and clinical features; and critically discuss the current classification scheme.

The Clinical Significance of Neuroendocrine Features in Invasive Breast Carcinomas

The latest World Health Organization (WHO) classification categorized invasive breast carcinomas (IBCs) with neuroendocrine (NE) differentiations into neuroendocrine neoplasms (including well-differentiated neuroendocrine tumor [NET] and poorly differentiated neuroendocrine carcinoma [NEC]) and IBC no special type with NE features (IBC-NST-NE). However, little is documented of the clinical significance of this classification; also the precise thresholds and choices of NE markers were variable. In the current study, a large cohort of patients with IBC with NE differentiation were morphologically classified based on the WHO criteria and the clinical relevance of expression of different NE markers (synaptophysin [SYN], chromogranin [CG], and CD56) was evaluated. Among 1,372 IBCs, 52 NET (3.8%) and 172 IBC-NST-NE (12.5%) were identified. Compared with the IBC-no NE cases, NET and IBC-NST-NE were similarly associated with positive estrogen receptor (ER) expression and lower grade (p < .001). For patient outcome, IBC-NST-NE, but not NET, demonstrated significantly worse survival than the IBC-no NE cases. Based on high (≥50%) and low (<50%) expression for each NE marker, independent poor disease-free survival for SYN^lo CG^lo and SYN^hi CG^lo cancers (IBC-no NE cases as references, hazard ratio [HR], ≤1.429; p ≤ .026) was found. Interestingly, SYN and CG expression correlated with each other and they shared similar clinicopathologic characteristics; but not with with CD56. In addition, CD56-only positive cases were associated with hormone receptors negativity and basal markers positivity (p ≤ .019), and patients' outcome was similar to IBC-no NE cancers. Our findings suggested that NE markers expression may provide information to fine tune treatment strategy. The relevance of CD56 as NE marker requires further studies. IMPLICATIONS FOR PRACTICE: Invasive breast carcinomas (IBCs) with neuroendocrine (NE) differentiation are heterogeneous in clinicopathologic parameters, biomarker expression, and prognosis. However, there are no specific therapies targeting NE differentiation, and all carcinomas with any NE differentiation are treated similarly as other IBCs. The results of this study suggest that stratification based on NE marker expression levels may provide added prognostically pertinent information, aiding better treatment strategy. In addition, CD56-only positive carcinomas showed a different clinicopathologic and biomarker expression profile compared with those with chromogranin and synaptophysin expression. Relevance of CD56 as an NE marker requires further studies.

Evolving concepts in prostatic neuroendocrine manifestations: from focal divergent differentiation to amphicrine carcinoma

Prostatic neuroendocrine manifestations encompass a heterogeneous spectrum of morphologic entities. In the era of evidence-based and precision-led treatment, distinction of biologically relevant clinical manifestations expanded the evolving clinical role of pathologists. Recent observations on the occurrence of hormone therapy-induced aggressive prostatic cancers with neuroendocrine features have triggered the need to refine the spectrum and nomenclature of prostatic neuroendocrine manifestations. Although the morphologic assessment still remains the basis of the diagnostic workup of prostatic neoplasms, the application of ancillary biomarkers is crucial in the accurate classification of such presentations. This review provides a diagnostic roadmap for the practicing pathologist by reviewing the characteristic morphologic, immunohistochemical, and molecular correlates of various faces of prostatic neuroendocrine manifestations.

Comprehensive clinical and molecular analyses of neuroendocrine carcinomas of the breast

Neuroendocrine breast carcinomas represent a rare subtype of breast cancer. Their definition, prevalence, and prognosis remain controversial in the literature. The 2012 WHO classification of breast cancer categorizes neuroendocrine carcinomas into three morphologically distinct subtypes: well-differentiated neuroendocrine tumors, poorly differentiated neuroendocrine carcinomas, and invasive breast carcinomas with neuroendocrine differentiation. We aimed to gain insight into the clinical, morphologic, phenotypic, and molecular features of 47 neuroendocrine breast carcinomas. Targeted next-generation sequencing by an AmpliSeq 22 cancer gene hotspot panel and the Prosigna assay were performed on 42/47 and 35/47 cases, respectively. Average age at diagnosis was 69 years. All tumors were estrogen receptor-positive and the large majority expressed progesterone receptor (89%), GATA3 (98%), FOXA1 (96%), and CK8/18 (98%). There was an almost equal distribution of luminal A (52%) and B (48%) carcinomas. Almost half of the cohort (49%) displayed a high risk of recurrence score with the Prosigna test. Patients with a neuroendocrine carcinoma had a shorter disease-free survival compared with those affected by carcinomas of no special type matched for age, size, grade, and estrogen receptor status. No significant differences were observed in terms of overall survival. Stratification of neuroendocrine carcinomas using the 2012 WHO criteria did not reveal statistically significant differences among the distinct categories (well-differentiated neuroendocrine tumors, poorly differentiated neuroendocrine carcinomas, and invasive breast carcinomas with neuroendocrine differentiation), in terms of either progression-free or overall survival. Our targeted sequencing analysis found three cases (7%) harboring a PIK3CA mutation, and in three other cases (7%) TP53 mutations were detected. This study showed that neuroendocrine breast carcinoma is a distinct subtype of luminal carcinoma with a low rate of PIK3CA mutations and with an aggressive clinical behavior. An accurate identification of neuroendocrine differentiation may be useful to better tailor patient adjuvant therapy within luminal carcinomas.

[Neuroendocrine neoplasms of the breast]

Neuroendocrine neoplasms (NEN) of the breast are specific tumor entities. According to the literature up to 5% of breast neoplasms are malignant epithelial neoplasms of the breast. They are defined by a neuroendocrine (NE) architecture and cytology combined with an expression of the neuroendocrine vesicle markers chromogranin A and/or synaptophysin. The diagnosis is supplemented by the receptor status and the proliferative activity. According to the World Health Organization (WHO) classification of 2012 the following groups of NEN are distinguished: (1) invasive breast carcinoma with NE differentiation, (2) well-differentiated neuroendocrine tumor (NET) and (3) poorly differentiated small cell carcinoma (NEC). This review article focuses on (1) the definition and basic principles of diagnostics, (2) the history, nomenclature and WHO classification from 2003 and 2012, (3) the frequency of breast NEN, (4) the hereditary background and functional activity, (5) the expression of receptors and (6) the possible clinical implications. In addition, the first results of a retrospective single center study (n = 465 patients with breast cancer over a time period of 4 years) on the frequency of NEN of the breast at the Breast Center of the University Hospital Düsseldorf are presented. In this study a frequency of 4.5% of NEN was found based on a diagnostic cut-off of > 50% Chromogranin A and/or synaptophysin positive tumor cells.

Working formulation of neuroendocrine tumors of the skin and breast

In the skin and breast, endocrine tumors are composed of a heterogeneous mixture of endocrine and exocrine cells. The definition of "pure" endocrine carcinomas is a matter for debate, and as a consequence, there is lack of uniform diagnostic criteria. There are no significant clinical differences in either overall or disease-free survival between matched neoplasms with endocrine and without endocrine differentiation nor between the degree of endocrine differentiation and tumor size, stage, or prevalence of vascular invasion for both sites (skin and breast). Here, endocrine tumors of the skin and breast are grouped respectively into three categories that include most of the neuroendocrine tumors of the skin and breast as seen in routine practice. It was felt that the number of different types of neuroendocrine tumors is so conspicuous that it is impossible to organize them in an orderly classification. It has been proposed therefore, for practical diagnostic routine purposes, to arrange these neoplasms into a working formulation. The latter includes heterogeneous lesions respectively of the skin and breast within the same group that have clinical features in common.

Human achaete-scute homolog-1 expression in neuroendocrine breast carcinoma

Neuroendocrine (NE) breast carcinoma is defined by morphological features similar to those of NE tumors of other organs and NE marker expression in at least 50 % of neoplastic cells. However, a NE morphology may be observed even in breast carcinomas lacking NE markers. Human achaete-scute homolog-1 (hASH-1) is a transcription factor that plays a key role in the regulation of mammalian neural and NE cell development and has been identified in several human NE tumors. The aim of this study was to investigate hASH-1 expression in human breast cancers. hASH-1 expression was evaluated in 482 consecutive non-NE invasive breast carcinomas, in a series of 84 breast cancers with >50 % NE marker expression (high NE differentiation) and 21 carcinomas with NE histology but negative or focally (<50 %) positive for NE markers (low NE differentiation). hASH-1 protein was evaluated by a specific monoclonal antibody using immunohistochemistry and gene expression by real-time polymerase chain reaction. None of the non-NE invasive breast carcinomas expressed hASH-1 at any levels. hASH-1 was expressed in tumor cell nuclei of 63 and 38 % of cases with high and low NE differentiation, respectively. Strong correlation with protein and gene expression levels was observed (p < 0.0001). hASH-1 expression was correlated to a low mitotic count (p = 0.02) and a low Ki67 proliferative index (p = 0.0062). hASH-1 expression occurs in breast cancers with NE differentiation regardless of the extent of the NE cell population, and it is restricted to a subset of tumor cells having a low proliferative potential.

Neuroendocrine differentiation in breast cancer: established facts and unresolved problems

Neuroendocrine breast carcinoma (NEBC) diagnosis relies on (i) presence of morphologic neuroendocrine features, and (ii) neuroendocrine markers expressed in more than 50% of tumor cells. The World Health Organization classification describes 3 main histologic types: the solid, the small/oat cell, and the large cell variant. In addition, we have recently proposed a further categorization into 5 subgroups: the first 3 categories encompass solid lesions and include (i) solid cohesive carcinomas, (ii) alveolar carcinomas, and (iii) small cell carcinoma; the last subgroups include mucin-producing tumors which are (iv) solid papillary carcinomas and (v) cellular mucinous carcinomas. Chromogranin A and synaptophysin have been considered as the most sensitive and specific neuroendocrine markers in NEBC. At the molecular level, recent gene expression profiling studies have shown that NEBCs pertain to the luminal molecular type, being positive for hormone receptors and negative for HER2. Moreover, it has been demonstrated that mucinous and neuroendocrine carcinomas are transcriptionally distinct from conventional invasive ductal carcinomas. Following the above criteria, NEBCs constitute approximately 1% of all breast carcinomas. The clinical effect of neuroendocrine breast cancer is still a matter of debate; however, when compared with unselected breast cancers, NEBCs show a less aggressive clinical behavior.

[Mixed endocrine tumors]

Mixed endocrine tumors are tumors composed of at least two distinct tumor populations, one of which is endocrine. Because of their rarity and unusual presentation, endocrine mixed tumors raise many problems of diagnosis, management and therapy. Three main types of endocrine mixed tumors are recognized: The existence of these various types has been confirmed by recent molecular studies, even if the same studies have also shown that the histogenesis of a mixed endocrine tumor cannot be predicted from its histological features. Composite tumors are the less rare mixed tumors. The recent WHO classification recommends to restrict the term of composite endocrine tumor to the epithelial tumors containing at least 30% of obviously tumoral endocrine cells; some authors recommend to use higher thresholds, of at least 50%, in order to avoid overdiagnosis. The endocrine component is usually well differentiated, easily identified by its suggestive histological features; the endocrine nature of tumor cells is confirmed by the immunodetection of specific endocrine and neuro-endocrine markers (such as chromogranin A and synaptophysin). In some cases, the endocrine component is poorly differentiated: the demonstration of neuro-endocrine markers is necessary to confirm the diagnosis. Mixed tumors can occur in every anatomical site; they are more frequent in organs containing endocrine cells in the normal state (especially the digestive tract and the pancreas), but they can also be observed in organs devoid of endocrine cells (such as the mammary gland). The management of mixed endocrine tumors must take into account the more aggressive component. Mixed tumors containing a well differentiated endocrine component and an adenocarcinomatous component are to be treated like adenocarcinomas. Mixed tumors containing a poorly differentiated endocrine component must be considered as poorly differentiated endocrine carcinomas.

Mucinous carcinoma of the breast with neuroendocrine differentiation

A case of mucinous carcinoma of the breast with neuroendocrine differentiation in an 89-year-old woman is presented. The patient presented with a rapidly growing right breast mass, which she had had for 2-3 years. The tumor, 15 x 8 x 5 cm, was located mainly in the upper outer quadrant. Light microscopy revealed a pure mucinous carcinoma of type B. Neuroendocrine differentiation was demonstrated by Grimelius stain and chromogranin A, as well as the presence of neurosecretory granules. The breast cancer cells were of luminal origin and had dedifferentiated to attain neuroendocrine properties.

Mucinous carcinoma of the breast: a multifaceted study with special reference to histogenesis and neuroendocrine differentiation

Although mucinous carcinoma (MC) of the breast is considered to originate from ductal carcinoma, it is not known whether mucinous growth begins in the intraductal carcinoma or later in the invasive carcinoma. In this study, 33 MC (16 pure without any ductal components, 10 mixed Type I with an intraductal component, seven mixed Type II with a common invasive ductal carcinoma (IDC) component)) were examined to clarify the time when mucinous growth begins. Histochemical and immunohistochemical examinations of mucin revealed that mucinous growth can begin in the intraductal carcinoma and in the common IDC. Histological transition and clonality analysis using microsatellite markers supported that some MC originate from common IDC. The pure type of MC probably originates from the intraductal carcinoma, showing a micropapillary feature. Neuroendocrine differentiation, known to be associated with MC, seemed to create the main progress in the typical MC. Moreover, we analyzed the factors of a worse prognosis of mixed MC Type II, which was strongly suggested by the lymph node status. However, no explainable differences on the cell proliferating ability, or c-erbB-2 and p53 protein overexpression were found.

Amphicrine tumor

The term amphicrine refers to cells, and tumors, which show both exocrine and endocrine features. Author s aim was to analyse the characteristics of these neoplasms. 40 suspicious cases were reviewed. Mucin-stains (PAS, diastase-PAS, Stains-all, Alcian-blue), immunohistochemistry (antibodies against Neuron-Specific Enolase (NSE), and Chromogranin A (CGA), and electronmicroscopic studies were performed to demonstrate exocrine and/or endocrine features of the tumor cells. By means of these methods, 16 cases turned out to be amphicrine tumors. Among them, there were 4 sinonasal, 1 bronchial, 1 mediastinal, 8 gastrointestinal and 2 suprarenal gland neoplasms. In connection to the subject, a brief review is given of amphicrine tumor, regarding its etiological and pathological aspects. These tumors form a distinct clinicopathological entity and should be separated from both neuroendocrine tumors and adenocarcinomas.

Solid papillary carcinoma of breast: an ultrastructural study

Solid papillary carcinoma of the breast is a subset of papillary carcinoma, which occurs in older women and usually has a favorable prognosis. It is primarily intraductal but also is often associated with invasive carcinoma, especially mucinous carcinoma. Intracellular and extracellular mucin is also found in the in situ stage, in most tumors. In addition to forming solid papillary masses, the cells palisade around vessels in pseudorosettes and show minimal nuclear atypia. Some cells show neuroendocrine differentiation, based on argyophilia with Grimelius staining. Four examples of this neoplasm were studied electron microscopically. Myoepithelial cells were not found. Neoplastic cells had an ultrastructure that was generally similar to that of other types of mammary carcinoma. There were extracellular microlumens, but intracellular lumens and pseudolumens were few or absent. Secretory activity varied among cells, and those cells appearing active had a variety of granule types, including typical flocculent and "bull's-eye" mucinous granules, small dense-core granules, and large serous-like granules. Some of the dense-core granules were interpreted as neuroendocrine in nature, based on their abluminal or juxtavascular location, whereas others that were apical and subluminal were probably mucinous in type. The large serous-appearing granules were subluminal in some cells and diffuse in others and may also have represented a variant of mucinous granules. The results support earlier opinions that accurate interpretation of specific granular function at the electron microscopic level depends on cytochemical studies using uranaffin as a marker of neuroendocrine activity. Although mucinous granules are identified by their lack of staining with uranaffin, the nature of the serous-appearing granules would still not be answered by this method; that is, a negative reaction would not define whether the granules are truly serous, or simply another form of mucin. Regardless of limitations of this type, correlation and extrapolation of histochemical (Grimelius and Alcian blue) and immunohistochemical (chromogranin and synaptophysin) results with subcellular structure are still very useful in establishing cell type.

The expression of keratins, vimentin, neurofilament proteins, smooth muscle actin, neuron-specific enolase, and synaptophysin in tumors of the specific glands in the canine anal region

Eight canine tumors originating from specific glandular structures in the anal region, as well as metastatic tumor tissue of two of these cases (case Nos. 7, 8), were immunohistochemically analyzed using various monoclonal antibodies (MoAbs) directed against human keratin types, vimentin, neurofilament proteins, and alpha-smooth muscle actin. These tumors also were stained for the broad-spectrum neuroendocrine markers neuron-specific enolase (NSE) and synaptophysin. In histologically normal canine anal structures, alpha-smooth muscle actin and NSE antibodies stained basally localized (probably myoepithelial) cells in the anal glands and the anal sac glands. NSE staining also was present in a limited number of luminal cells in both anal glands and anal sac glands. Synaptophysin labeling was not observed in any of these glandular structures. Histologically, the tumors were differentiated into well- and moderately differentiated perianal gland tumors (n = 5) and carcinomas without perianal gland differentiation (n = 3), corresponding to the so-called apocrine carcinomas of the anal region. Immunohistochemically, the perianal gland tumors could be differentiated from the carcinomas by marked differences in staining pattern with the various keratin MoAbs, particularly MoAbs directed against human keratin types 7 and 18. The keratin-staining characteristics of the carcinomas suggest a glandular luminal cell origin. Metastases of the carcinomas showed loss of some keratin-staining characteristics as compared with the primary tumor. Staining for NSE was only observed in solitary cells and small cell clusters in the carcinomas and their metastases, whereas the alpha-smooth muscle actin antibody did not react with the carcinoma cells. None of the tumors stained for neurofilament proteins or synaptophysin. An unequivocal neuroendocrine nature of the carcinomas could not be substantiated by our immunohistochemical study, although the presence of a population of neuroendocrine cells within these neoplasms seems likely. Because the immunohistochemical features of the carcinomas with respect to various keratin MoAbs and NSE are similar to those of the anal glands and the anal sac glands, both these glands might be considered as site of origin of these carcinomas.

Ultrastructural immunolabeling in the evaluation, diagnosis, and characterization of neuroendocrine neoplasms

Neuroendocrine neoplasia represents a heterogenous entity with variable morphologic light microscopic expressions. In many cases a definite diagnosis is easily made by light microscopic examination, but in some cases this does not suffice. In the latter instances, immunocytochemistry, ultrastructural examination, or both are required to diagnose a neuroendocrine neoplasm. However, basing a diagnosis of neuroendocrine neoplasia exclusively on the results obtained from immunocytochemical or ultrastructural evaluation of these tumors may not be entirely accurate in some instances. Ultrastructural immunolabeling plays a key role in accurately defining localization of immunoreactive substances in well-characterized neuroendocrine neoplasms, can assess colocalization of antigenic epitopes, helps define specificity and significance of immunocytochemistry results obtained at the light microscopic level, and is more sensitive than light microscopic immunocyto-chemistry. Some evolving diagnostic entities can be further characterized by utilization of ultrastructural labeling techniques. Controversies concerning the neuroendocrine nature of electron-dense structures identifiable at the ultrastructural level can be readily and accurately resolved. By providing a way to evaluate combined immunomorphologic parameters, ultrastructural immunogold labeling can settle important questions pertaining to neuroendocrine neoplasia. The present article illustrates a series of cases where the above-mentioned applications were tested.

Fine-needle aspiration biopsies of metastatic neuroendocrine tumors in liver: use of transmission electron microscopy and protein A gold technique in diagnosis

Five fine-needle aspiration biopsies of liver were studied to evaluate the use of electron microscopy and protein A gold technique in the diagnosis of metastatic neuroendocrine tumors. All five cases had cytologic features suggestive of neuroendocrine tumors and neurosecretory granules on ultrastructural examination. The aspirates were stained by the immunoperoxidase technique and the postembedding protein A gold technique using the antibody to chromogranin A. Three cases were positive for chromogranin A by both immunoperoxidase and protein A gold techniques. Two cases were positive by protein A gold technique and negative by immunoperoxidase technique. Confirmation of neurosecretory granules by immunochemistry is ideal, since ultrastructurally they can be mimicked by other electron-dense inclusions. Advantage of the protein A gold technique is the use of the same material for both ultrastructural evaluation and the protein A gold technique.

Argyrophilic neuroendocrine carcinoma of the male breast

A case of breast carcinoma with neuroendocrine features occurring in an elderly male patient is reported. Histologically, the tumor was characterized by solid growth with nests and ribbons of small to medium-size uniform neoplastic cells. Argyrophilia, expression of chromogranins at both protein and gene level, and the presence of dense granules of the neurosecretory type by electron microscopy were demonstrated.

Immunogold detection of chromogranin A in the neuroendocrine tumor

Immunogold ultrastructural localization of chromogranin A in secretory granules within tumor cells provides convincing evidence of endocrine or neuroendocrine differentiation. A modified immunogold method (designed for use on osmicated tissue) produced positive labeling of small granules not only in well-differentiated tumors but also in poorly differentiated small cell tumors primary in lung, cervix, and skin; only a proportion of granules in some of the tumor cells were positively labeled. Many non-small cell lung tumors often stain focally positive for chromogranin A at the light microscopy level, and such tumors may also contain sparse, small, dense granules. Because positive labeling could not be demonstrated over small granules in non-small cell lung tumors, the theory that such tumors are neuroendocrine in type may be erroneous.

Reliability of criteria for ultrastructural identification of neuroendocrine granules

For full diagnostic use to be made of the neurosecretory granule, the range of sizes, forms, and staining qualities for this cytoplasmic organelle, along with the extent of its expression in various neoplasms, must be established. Neurosecretory type granules occasionally occur in nonneuroendocrine tumors. A series of carcinoids of the lung provides a model for assessing the morphologic types of cytoplasmic granules identified by antibodies to chromogranin A and immunogold labeling. The results show that granule structure in tumors is pleomorphic. Despite having sizes within the expected range, many labeled and, indeed, unlabeled secretory granules are atypical, particularly in structural form. Cell-to-cell variation in the proportion of even typical neurosecretory granules labeling for chromogranin A is the rule. Studies correlating biochemical, immunohistochemical, electron microscopic, and perhaps in situ hybridization characteristics are required to define better the criteria for unequivocal identification of neurosecretory granules in tumors.

The nature of breast dense core granules: chromogranin reactivity

Ultrastructural immunoreactivity for chromogranin with the LK2H10 antibody was examined in nine cases of breast carcinoma and one example of normal resting breast. These tissues were selected for study on the basis of argyrophilia or LK2H10 immunostaining by light microscopy. In two cases, positive reactivity with the chromogranin antibody was seen in breast neuroendocrine-like dense core granules. In a further six cases chromogranin reactivity was not seen in similar granules that showed the neuroendocrine properties of ultrastructural argyrophilia and uranaffinity. Inability to exhibit the full complement of neuroendocrine characteristics in breast carcinomas contrasts with the facility to demonstrate them in tissues of usual neuroendocrine differentiation. Furthermore, in two mucoid carcinomas and one example of normal resting breast ultrastructural cytoplasmic LK2H10 reactivity was evident, which was not localized to dense core granules, although these were present in two of the cases. Our findings demonstrate the heterogeneity of breast dense core granules and discourage acceptance of such characteristics as evidence of histogenesis of these carcinomas from a neuroendocrine cell type in breast tissue.

Primary oat cell (neuroendocrine) carcinoma of the breast. Report of four cases

Four cases of oat cell (neuroendocrine) carcinoma of the breast are reported. Three patients died within 15 months of the diagnosis and the fourth patient is alive after 44 months. Histochemical, ultrastructural and mRNA markers of endocrine differentiation were present in three cases. These tumours show histological similarities to breast metastases of bronchial oat cell carcinoma, but a distinguishing feature is the presence of in situ ductal lesions. It appears that the breast is a further site which has to be added to the long list of extrapulmonary oat cell carcinomas.

Small cell carcinoma of the gallbladder combined with adenocarcinoma

A rare case of small cell carcinoma (SCC) of the gallbladder combined with adenocarcinoma is reported. The patient was a 70-year-old Japanese man, who died of the disease shortly after the onset of symptoms. Autopsy disclosed a small tumor (1.0 cm in longest diameter) in the fundus of the gallbladder, with widespread metastasis. Histochemically, the tumor cells showed negative reactions for argyrophilic and argentaffin stainings, a weak immunohistochemical reaction only for neuron-specific enolase, and negative reactions for all of the other neurosecretory markers used, including neurofilament, chromogranin, somatostatin, gastrin and leu-7. However, electron microscopic examination revealed a few typical neurosecretory granules (NSG) in the cytoplasm of some tumor cells. We suggest that: 1. The presence of NSG in the cytoplasm of tumor cells is the most reliable diagnostic criterion for SCC. 2. SCC, at least the combined type, arises from a multipotential stem cell.