Neuroendocrine carcinomas of the skin: light microscopic, ultrastructural, and immunohistochemical analysis

Three primary skin carcinomas were analyzed by light microscopy, immunohistochemistry, and electron microscopy. In all cases, local recurrences, regional lymph node metastases, distant metastases, or all three developed. One patient had elevated serum calcitonin levels that did not decrease after thyroidectomy but did return to normal after removal of the skin tumor recurrences, its metastases, or both. The tumor cells were arranged in solid clusters; a trabecular arrangement was occasionally seen. In 2 cases the cells were of intermediate size and showed vesicular central nuclei and pale, moderately abundant cytoplasm. In the remaining case the cells were distinctly smaller and either round or fusiform. Mitoses were more abundant in the latter case than in the former two. By immunohistochemistry, calcitonin- and somatostatin-containing cells were demonstrated in all cases and ACTH in one. By electron microscopy, the cases consisting of intermediate-size cells displayed moderately abundant neurosecretory-type granules irregularly dispersed throughout the cytoplasm. The case consisting of smaller cells displayed fewer and smaller granules that tended to concentrate in slender cytoplasmic processes. We conclude that these tumors constitute parts of the broadening spectrum of neuroendocrine skin carcinomas that may derive from Merkel cells.     

Neuroendocrine Carcinomas of the Skin: Light Microscopic,Ultrastructural, and Immunohistochemical Analysis

Three primary skin carcinomas were analyzed by light microscopy, immunohistochemistry, and electron microscopy. In all cases, local recurrences, regional lymph node metastases, distant metastases, or all three developed. One patient had elevated serum calcitonin levels that did not decrease after thyroidectomy but did return to normal after removal of the skin tumor recurrences, its metastases, or both.

The tumor cells were arranged in solid clusters; a trabecular arrangement was occasionally seen. In 2 cases the cells were of intermediate size and showed vesicular central nuclei and pale, moderately abundant cytoplasm. In the remaining case the cells were distinctly smaller and either round or fusiform. Mitoses were more abundant in the latter case than in the former two.

By immunohistochemistry, calcitonin- and somatostatin-containing cells were demonstrated in all cases and ACTH in one. By electron microscopy, the cases consisting of intermediate-size cells displayed moderately abundant neurosecretory-type granules irregularly dispersed throughout the cytoplasm. The case consisting of smaller cells displayed fewer and smaller granules that tended to concentrate in slender cytoplasmic processes.

We conclude that these tumors constitute parts of the broadening spectrum of neuroendocrine skin carcinomas that may derive from Merkel cells.     

Challenging differential diagnoses in small biopsies from the sinonasal tract

Sinonasal biopsy specimens are a challenging area in anatomic pathology. The small, often fragmented or crushed nature of these biopsies can hinder morphologic assessment. Additionally, many of the tumors in this area are rare and share morphologic, and sometime immunophenotypic similarities. In many cases, immunohistochemistry is helpful if not necessary to reach a specific diagnosis. In other cases, a specific diagnosis is not possible and a differential diagnosis must be given on a biopsy specimen despite access to a well-equipped immunohistochemistry laboratory. This review article groups some of the more challenging entities in the sinonasal region based on morphologic patterns. These include low grade squamoid lesions such as sinonasal (Schneiderian) papilloma and DEK::AFF2 rearranged carcinoma, glandular neoplasms such as intestinal and non-intestinal type sinonasal adenocarcinoma, high-grade carcinomas such as HPV-related multiphenotypic sinonasal carcinoma, NUT carcinoma and SWI/SNF deficient carcinomas, small round blue cell tumors such as teratocarcinosarcoma, neuroendocrine carcinoma and olfactory neuroblastoma, and finally, low grade spindle cell neoplasms such as glomangiopericytoma, biphenotypic sinonasal sarcoma and solitary fibrous tumor.     

Immunohistochemical and ultrastructural features of neuroendocrine differentiated carcinomas of the prostate: an immunoelectron microscopic study

The purpose of this study was to further define the immunohistochemical and ultrastructural characteristics of neuroendocrine (NE) differentiated prostatic carcinomas. Seventy-seven specimens were obtained from prostatic carcinoma tumors during prostatectomy, transurethral resection of prostate or biopsy in 77 prostate cancer patients, and analyzed by immunohistochemical staining for chromogranin A (CgA). Nine of these tumors were also studied by elctron microscopy and 4 were examined by pre-embedding immunoelectron microscopy. CgA-stained cells were detected in 36 tumors (47%). Clinically advanced tumors or tumors with higher histological grades were associated with increased NE differentiation. Three of the tumors studied by electron microscopy contained cells showing unequivocal NE differentiation revealed by the presence of neurosecretory granules, while the poorly NE-differentiated malignant cells contained pleomorphic granules, which were lysosomal-like rather than NE-type granules. Immunoelectron microscopy demonstrated the presence of CgA immunoreactivity on the pleomorphic granules in the poorly differentiated malignant glands. This study suggests that NE-differentiated malignant cells in prostate cancer tissues may induce aggressive behavior in adjacent proliferating neoplastic cells via a paracrine mechanism.     

Breast Carcinomas with Neuroendocrine Differentiation

Twenty-two breast carcinomas with membrane bound granules by electron microscopy were tested for the presence of neuron specific enolase (NSE), neuropeptides and serotonin by immunohistochemistry. By light microscopy the cases studied included infiltrating ductal carcinomas, intraductal carcinomas, apocrine carcinomas, infiltrating lobular carcinomas of both classical and alveolar types, mixed lobular/colloid carcinomas, carcinoid growth pattern and one unclassified carcinoma. Ten cases showed immunoreactivity for 1 or 2 neuropeptides in scattered cells whereas all cases were positively and rather diffusely stained with anti-NSE. Immunohistochemical staining at the ultrastructural level was carried out; the presence of neuropeptides could not be confirmed. Scattered granules were marked with gold particles when antiserum against casein was used.

We conclude that neither argyrophilia, nor NSE immunoreactivity nor membrane bound granules seen by electron microscopy constitute at present sufficient evidence to designate a breast carcinoma as neuroendocrine. However, our study indicates that certain breast carcinomas of several types do include cells with neuroendocrine features demonstrable convincingly by light microscopic immunohistochemistry. We have no evidence that these breast carcinomas with neuroendocrine features behave differently from their counterparts lacking such features. The intriguing speculation is that neuropeptides produced by certain breast carcinomas may act as local modulators of tumor growth and differentiation.     

Breast carcinomas with neuroendocrine differentiation

Twenty-two breast carcinomas with membrane bound granules by electron microscopy were tested for the presence of neuron specific enolase (NSE), neuropeptides and serotonin by immunohistochemistry. By light microscopy the cases studied included infiltrating ductal carcinomas, intraductal carcinomas, apocrine carcinomas, infiltrating lobular carcinomas of both classical and alveolar types, mixed lobular/colloid carcinomas, carcinoid growth pattern and one unclassified carcinoma. Ten cases showed immunoreactivity for 1 or 2 neuropeptides in scattered cells whereas all cases were positively and rather diffusely stained with anti-NSE. Immunohistochemical staining at the ultrastructural level was carried out; the presence of neuropeptides could not be confirmed. Scattered granules were marked with gold particles when antiserum against casein was used. We conclude that neither argyrophilia, nor NSE immunoreactivity nor membrane bound granules seen by electron microscopy constitute at present sufficient evidence to designate a breast carcinoma as neuroendocrine. However, our study indicates that certain breast carcinomas of several types do include cells with neuroendocrine features demonstrable convincingly by light microscopic immunohistochemistry. We have no evidence that these breast carcinomas with neuroendocrine features behave differently from their counterparts lacking such features. The intriguing speculation is that neuropeptides produced by certain breast carcinomas may act as local modulators of tumor growth and differentiation.     

Small cell carcinoma of the kidney: a case report and review of the literature

Small cell carcinoma is a malignant tumor composed of small cells with a diffuse growth pattern. It has immunohistochemical and ultrastructural features of both neuroendocrine and epithelial neoplasms. These tumors constitute 10% to 20% of malignant tumors in the lung, which is their most frequent site. They have been described in other extrapulmonary sites, where they are defined using the same criteria as used in the lung. These tumors are rarely found in the genitourinary tract. Fewer than 30 cases have been reported in the kidney. The differential diagnosis mainly includes other small round cell tumors and metastatic small cell lung carcinoma. We present and discuss a primary small cell carcinoma of the kidney (to our knowledge the 9th to be reported in the literature), which we studied with light microscopy, immunohistochemistry, electron microscopy, and, for the first time, flow cytometry.     

Coexpression of neuroendocrine markers and epithelial cytoskeletal proteins in bronchopulmonary neuroendocrine neoplasms

Neuroendocrine (NE) neoplasms of the human bronchopulmonary tract were examined by electron microscopy, immunocytochemistry, and gel electrophoresis of cytoskeletal proteins from microdissected tissue samples. All samples (carcinoids, well-differentiated NE carcinoma, NE carcinomas of intermediate type, NE carcinomas of the small cell type) contained significant numbers of cells that immunostained for one or more of the following neuroendocrine markers tested: bombesin, calcitonin, ACTH, leu-enkephalin, gastrin, serotonin, somatostatin, alpha-melanocyte-stimulating hormone, vasoactive intestinal peptide, glucagon, insulin, substance P, and neuron-specific enolase. Electron microscopy revealed typical NE cell features, including variable abundant and frequently heterogeneous neurosecretory granules. Tumor cells contained filaments specifically stained with different conventional and monoclonal antibodies to cytokeratins and displayed punctate plasma membrane staining with antibodies to desmoplakins, in agreement with the electron microscopic demonstration of tonofilament bundles and desmosomes. Immunocytochemistry for NE markers and cytoskeletal proteins on consecutive sections revealed both cytokeratins and neuroendocrine substances in single cells. Using gel electrophoresis of cytoskeletal proteins of tissue regions extracted with high salt buffer and detergent, we could detect, in the tumors tested, appreciable amounts of cytokeratin polypeptides 8, 18, and 19, i.e., major cytokeratins also found in certain other lung carcinomas such as adenocarcinomas. Tumor cells were not significantly stained with antibodies to other intermediate filament proteins such as vimentin, desmin, glial filament protein, and neurofilament protein. The results show that NE substances can be synthesized in cells containing a typical epithelial cytoskeleton, i.e., cytokeratin filaments and desmosomes. These findings support the notion of an epithelial character of these tumors and appear in contrast with recent reports that neurofilaments are the only type of intermediate filaments present in carcinoids and other pulmonary NE tumors. These observations may have important implications for the histogenesis of NE carcinomas and for diagnostic pathology.     

Ultrastructural Features of Neuroendocrine Differentiated Carcinomas of the Breast

The ultrastructural patterns of neuroendocrine (NE) differentiated breast carcinomas are analyzed and discussed. Reports in the literature describe wide variations in the size of observed dense-core membrane-bound granules and discrepancies in their interpretation. In the present study 24 cases of breast carcinoma with recognized morphologic, histochemical, and immunocytochemical features of NE tumors were investigated. Five different types of dense-core granules of neurosecretory (NS) type (confirmed by the ultrastructural localization of chromogranin A) and five different cell types were recognized. Some amphicrine cells were found to contain both mucin and NS granules. Another notable ultrastructural feature of breast NE carcinomas was the presence of clear vesicles of presynaptic type, which correlated with expression of synaptophysin.     

Mucinous breast carcinomas with abundant intracytoplasmic mucin and neuroendocrine features: light microscopic, immunohistochemical, and ultrastructural study

Eight mucinous carcinomas of the breast were studied by light microscopy and immunohistochemistry; one was studied by electron microscopy. All 8 cases had abundant, relatively clear cytoplasm that contained mucin. Cells were argyrophil positive and argentaffin negative. Eight cases were positive for neuron specific enolase (NSE), 5 cases for serotonin, 1 case for serotonin and somatostatin and 2 cases for serotonin, somatostatin, and gastrin. None had clinical evidence of abnormal neuroendocrine function. Three patients had axillary lymph node metastases. Only 1 of 5 patients in whom there was clinical followup died of her disease. Electron microscopy of one case showed abundant intracytoplasmic and extracellular mucin, round and pleomorphic dense-core granules, numerous cell processes, and aggregates of intermediate filaments. These cases expand the histologic spectrum of breast carcinomas which may show neuroendocrine differentiation.     

Neuroendocrine Carcinomas with Multiple Immunoreactive Peptides and Melanin Production

Two primary neuroendocrine skin carcinomas, one bronchial carcinoma, and one typical medullary thyroid carcinoma have been shown by immunohistochemistry and electron microscopy to contain two or more immunoreactive peptides as well as melanosomes and premelanosomes. Of the battery of antisera tested, somatostatin was the only material present in all four tumors; calcitonin and ACTH were present in three of the four neoplasms. Neurosecretory granules on the one hand and melanosomes on the other were more readily identifiable in separate cells. However, in at least 2 cases, individual cells were thought to contain both types of structures.

Of the various explanations possible, we choose to interpret these tumors as complex neuroendocrine carcinomas comprising cellular populations capable of synchronous production of immunoreactive peptides and melanin. Since melanocytes are members of the dispersed neuroendocrine (APUD) system, these observations may not appear entirely surprising. Noteworthy, however, is that melanin synthesis seemingly remains a synchronously available option to neoplastic neuroendocrine cell populations of possibly diverse histogenesis that are actively engaged in the production of multiple hormonal peptides. We consider that these phenomena represent yet another facet of neoplastic multidirectional differentiation.

It is possible that the determination of immunoreactive peptides as “markers” may play a future role in the diagnosis, therapy, and prognosis of these and similar tumors and in the study of the dysplasias that may precede them.     

Histopathological and immunohistochemical study of neuroendocrine tumors of the rectum

A clinicopathological and immunohistochemical study was carried out on 32 cases of neuroendocrine tumors of the rectum. Typical carcinoids consisted of 27 cases, histologically showing uniform round to columnar cells forming solid alveolar nests and ribbon-like or trabecular arrangement. Neuroendocrine carcinomas consisted of 5 cases in which tumor cells with prominent nuclear atypism were arranged in a ribbon-like or trabecular fashion and formed gland-like structures. There were also small round tumor cells resembling lymphocytes. The prognosis of neuroendocrine carcinomas is very poor with marked tumor invasion of lymphatics and veins resulting in liver metastases and death within one year after operation. Thirty cases out of the 32 showed a positive argyrophil reaction, while immunohistochemistry of 29 cases revealed more than one peptide hormone in 23 cases. The most common hormone was somatostatin being present in 18 of the 23 tumors and glucagon in 16 of the 23 tumors. Gastrin/CCK and calcitonin were proven in 6 of the 23 tumors and in 4 of the 23 tumors, respectively. On the other hand, more than two hormones was present in 15 of the 23 tumors examined. Histologically, neuroendocrine tumors have a very wide spectrum. Histogenetically, typical carcinoids and neuroendocrine carcinomas are considered to be of the same origin with the former showing morphological and functional differentiation to endocrine cells and the latter being more undifferentiated.     

Small Cell Undifferentiated Carcinoma of the Uterine Cervix: Histology, Ultrastructure, and Immunohistochemistry of Two Cases

Two clinical stage IB small cell undifferentiated carcinomas (SCUC) of the cervix were studied by light and electron microscopy and immunohistochemistry. Both cases occurred in women aged less than 31 years. Despite radical hysterectomy and external pelvic radiotherapy, both patients died of recurrent disease within 14 months after initial therapy. The tumors consisted of sheets of closely packed, uniform small, round to oval cells with hyperchromatic nuclei and scant indistinct cytoplasm. One case was associated with cervical squamous cell carcinoma. The neoplastic cells had few organelles and desmosome-like junctions and lacked mucinous or neurosecretory granules or tonofilaments. Immunohistochemistry failed to reveal S-100, CEA, neuropeptides or neuron-specific enolase.

SCUC probably arises either from basal cells of the cervical squamous epithelium, or gland cells of the endocervical epithelium, or still from subcolumnar endocervical reserve cells. Based on ultrastructure and immunohistochemistry, SCUC seems to represent the undifferentiated variant of small cell neuroendocrine tumors of the cervix.     

Squamous Cell Carcinoma with Anemone Cell Features

A tumor from a 52-year-old Albino male had the ultrastructural features of an anemone cell tumor. Evidence of squamous differentiation was seen by electron microscopy and immunohistochemistry. “Anemone cell” tumors have been shown to be classifiable as either carcinomas or lymphomas; the term therefore does not describe a discrete entity or constitute a definitive diagnosis. Treatment with radiotherapy was successful in this case, while chemotherapy appeared to have little effect.     

Immunohistochemical and Ultrastructural Analysis of Bronchopulmonary Neuroendocrine Neoplasms. II. Well-Differentiated Neuroendocrine Carcinomas

We have attempted to characterize a group of bronchopulmonary neoplasms that share certain structural features with true carcinoids but appear distinctly more pleomorphic and behave far more aggressively. In reviewing our files from 1973 to 1982, 11 such neoplasms were identified; the original diagnoses were “atypical bronchial carcinoid” (3 cases), “malignant carcinoid” (1 case), “bronchial carcinoid” (3 cases), “peripheral carcinoid” (2 cases), and “peripheral oat cell carcinoma” (2 cases).

Of the 11 neoplasms, 5 were central and 6 were peripherally located. At presentation, 7 patients had lymph node rnetastases and 1 had a distant metastasis. No patient had a conventionally defined hormonal syndrome; however, 2 patients had a history of episodic flushing, one of which was associated with diarrhea.

All cases were studied by light microscopy and light microscopic immunohistochemistry for NSE (neuron-specific enolase), serotonin, and broad-spectrum neuropeptides. Five cases were studied by electron microscopy. By light microscopy, the tumors were composed of solid clusters of polygonal to fusiform cells in an evident organoid arrangement. Foci of glandular and/or squamous differentiation were seen in 7 cases. Pleomorphism was moderate and mitoses were readily found. Focal necrosis was seen. By immunohistochemistry, 10 cases expressed NSE immu-noreactivity. All cases demonstrated hormonal immu-noreactivity; in 9 cases, immunoreactivity for more than one hormone was observed. The hormones most frequently expressed were serotonin, bombesin, gastrin, leu-enkephalin, and ACTH.

By electron microscopy, all cases studied contained heterogeneous populations of neurosecretory granules; the latter, however, were not abundant and tended to aggregate either in the basal pole of the cells or, more frequently, in interlacing “dendritelike” cytoplasmic processes. Aggregates of intermediate filaments were frequently seen. Basal lamina deposition was seen but gaps and larger areas of discontinuity were frequent.

We believe that these neoplasms constitute a distinct pathologic entity for which the term “well-differentiated neuroendocrine carcinomay” has been proposed. Clinically, these tumors merit special attention since they are demonstrably more aggressive than true carcinoids but are distinctly less malignant than the intermediate or small cell variants of neuroendocrine carcinoma.     

Pituitary Carcinoma: An Ultrastructural Study of Eleven Cases

Pituitary carcinomas are very rare. Defined as adenohypophysial tumors that undergo craniospinal and/or systemic metastasis, most are PRL- or ACTH-producing. Their ultrastructural features, particularly relative to benign adenomas of similar functional type, have not been sufficiently explored. Eleven cases of immunohistochemically characterized pituitary carcinoma with documented cerebrospinal and/or systemic metastases were collected from various institutions and studied by transmission electron microscopy. The tumors were surgically removed from 7 women and 4 men ranging in age between 28 and 74 years (mean, 50 years). All were endocrinologically functioning. Six tumors secreted PRL; three were ACTH-producing; one each was GH/PRL- and TSH-producing. The patients with the ACTH-producing tumors had all presented with Cushing's disease and two of them had undergone adrenalectomy (Nelson syndrome). In most cases significant cellular atypia and mitotic activity were observed. In terms of morphologic features of functional differentiation, electron microscopy revealed that in 9 cases the tumor cells maintained at least some ultrastructural markers of their basic phenotype. A unique feature in 2 ACTH carcinomas was the variable admixture of smooth endoplasmic reticulum with intermediate (cytokeratin) filaments. In 2 cases, both PRL-producing carcinomas, the cell type comprising the tumor could not be identified on an ultrastructural basis alone. Ultrastructural investigation of pituitary carcinomas confirms their endocrine nature and, in most but not all cases, reveals their functional differentiation. Despite the diagnostic utility of electron microscopy in the assessment of theserare tumors, the distinction of pituitary carcinoma from pituitary adenoma cannot be firmly made on ultrastructural grounds alone.     

Pituitary carcinoma: an ultrastructural study of eleven cases

Pituitary carcinomas are very rare. Defined as adenohypophysial tumors that undergo craniospinal and/or systemic metastasis, most are PRL- or ACTH-producing. Their ultrastructural features, particularly relative to benign adenomas of similar functional type, have not been sufficiently explored. Eleven cases of immunohistochemically characterized pituitary carcinoma with documented cerebrospinal and/or systemic metastases were collected from various institutions and studied by transmission electron microscopy. The tumors were surgically removed from 7 women and 4 men ranging in age between 28 and 74 years (mean, 50 years). All were endocrinologically functioning. Six tumors secreted PRL; three were ACTH-producing; one each was GH/PRL- and TSH-producing. The patients with the ACTH-producing tumors had all presented with Cushing's disease and two of them had undergone adrenalectomy (Nelson syndrome). In most cases significant cellular atypia and mitotic activity were observed. In terms of morphologic features of functional differentiation, electron microscopy revealed that in 9 cases the tumor cells maintained at least some ultrastructural markers of their basic phenotype. A unique feature in 2 ACTH carcinomas was the variable admixture of smooth endoplasmic reticulum with intermediate (cytokeratin) filaments. In 2 cases, both PRL-producing carcinomas, the cell type comprising the tumor could not be identified on an ultrastructural basis alone. Ultrastructural investigation of pituitary carcinomas confirms their endocrine nature and, in most but not all cases, reveals their functional differentiation. Despite the diagnostic utility of electron microscopy in the assessment of theserare tumors, the distinction of pituitary carcinoma from pituitary adenoma cannot be firmly made on ultrastructural grounds alone.     

Sarcomatoid Carcinoma: An Ultrastructural Study with Light Microscopic and Immunohistochemical Correlation of 10 Cases from Various Anatomic Sites

The histogenesis of sarcomatoid carcinoma has been an intriguing topic for pathologists for many years, and considerable evidence has accumulated in the fields of tissue culture, electron microscopy, and immunohistochemistry to support the concept that the sarcomatous cells derive by way of “divergent differentiation” (metaplasia) from the carcinomatous elements. We have studied a group of 10 cases of these tumors from various organs, using detailed ultrastructural analysis as well as light microscopic and immunohistochemical correlation. We found that there is an ultrastructural spectrum of differentiation from epithelial to mesenchymal type features and that the malignant spindle cells may be purely epithelial (3 cases), purely mesenchymal (3 cases), or a mixture of both (4 cases). Furthermore, individual cells may show biphasia, having desmosomes and tonofibrils as well as well developed rough endoplasmic reticulum and filaments with dense bodies. Electron microscopic and immunohistochemical results do not always correlate, illustrating the prudence of using several keratin antibodies, including wide-spectrum ones, and of performing electron microscopic examination on these tumors.     

Application of electron microscopy in the diagnosis of fine needle aspiration biopsies and tumorous pleural effusion]

Forty-five cases of fine needle aspiration biopsies of tumor and 9 cases of tumorous pleural effusion specimens were reviewed electron microscopically for diagnosis. Among them, electron microscopical diagnosis of 22 cases (40.7%) was valuable, and that of 28 cases (51.8%) was of no diagnostic significance. In 14 out of 22 cases (63.6%) the nature and origin of tumor were further confirmed by electron microscopy, and in 8 cases (36.4%) electron microscopical diagnoses were consistent with light microscopic diagnoses. It was shown that in cytological diagnosis of tumors, electron microscopy was superior to light microscopy in defining the nature and origin of tumors, and in differentiating neuroendocrine tumors, leukemia and small round cell tumors.     

Neuroendocrine carcinomas: Role of immunocytochemistry and electron microscopy

Neuroendocrine tumors occur in many sites of the body and can present significant diagnostic problems when poorly differentiated. To identify a tumor as neuroendocrine, pathologists commonly use either immunocytochemistry or electron microscopy. In this report, the various immunocytochemical reagents are reviewed along with the ultrastructural features of neuroendocrine tumors. Site-specific variations in neuroendocrine tumors are discussed. A cost-effectiveness evaluation was performed on tumors from one laboratory which showed that electron microscopy was a less expensive diagnostic modality if more than three antibodies were necessary to arrive at the correct pathological diagnosis.