Metastatic Spindle Cell Malignant Melanoma with Prominent Microvilli

A metastatic spindle cell malignant melanoma with positive immunoreactivity for S-100 protein and HMB-45 antigen and the presence of premelanosomes is described in a lymph node of the neck 11 years after removal of a superficial spreading malignant melanoma from the arm. Ultrastructurally, long, slender microvilli created a pattern with great similarity to an anemone cell tumor. A more solid pattern without microvilli was also present. Despite the abundance of microvilli in the anemone part of the tumor, intracytoplasmic lumina were not observed. In addition, crystalline structures within enlarged mitochondria and intracisternal tubules were noted.     

Metastatic Spindle Cell Malignant Melanoma with Prominent Microvilli

A metastatic spindle cell malignant melanoma with positive immunoreactivity for S-100 protein and HMB-45 antigen and the presence of premelanosomes is described in a lymph node of the neck 11 years after removal of a superficial spreading malignant melanoma from the arm. Ultrastructurally, long, slender microvilli created a pattern with great similarity to an anemone cell tumor. A more solid pattern without microvilli was also present. Despite the abundance of microvilli in the anemone part of the tumor, intracytoplasmic lumina were not observed. In addition, crystalline structures within enlarged mitochondria and intracisternal tubules were noted.     

Ultrastructural Confirmation of Malignant Melanoma

We have recently had the opportunity to examine two cases, where malignant melanoma was suspected on light microscopy and Fontana-Masson stain was focally and faintly positive. Electron microscopy of four to five different blocks failed, however, to demonstrate the presence of premelanosomes and thereby to confirm the diagnosis of malignant melanoma. The areas in the paraffin blocks that on Fontana-Masson stain had showed a positive reaction were deparaffinized, embedded in plastic, and examined by electron microscopy. Now the characteristic premelanosomes were found and the diagnosis of malignant melanoma was confirmed.     

Metastatic Melanoma with Balloon Cell Changes: An Electron Microscopic Study

A case of metastatic balloon cell melanoma is presented. The balloon cells are ultrastructurally characterized by the presence of numerous cytoplasmic vacuoles and abnormal melanosomes, which confirm their melanocytic origin. The study supports the concept that the cytoplasmic vacuoles represent grossly dilated melanosomes. The value of electron microscopic examination is emphasized in order to distinguish these lesions from other malignant clear cell tumors.     

Metastatic Melanoma with Balloon Cell Changes: An Electron Microscopic Study

A case of metastatic balloon cell melanoma is presented. The balloon cells are ultrastructurally characterized by the presence of numerous cytoplasmic vacuoles and abnormal melanosomes, which confirm their melanocytic origin. The study supports the concept that the cytoplasmic vacuoles represent grossly dilated melanosomes. The value of electron microscopic examination is emphasized in order to distinguish these lesions from other malignant clear cell tumors.     

Malignant Melanoma of Soft Parts: An Ultrastructural Study of Four Cases

Samples from three clinically functional retroperitoneal paragangliomas were studied by light and electron microscopy. The tumors exhibited a Zellballen pattern histologically, and ultrastructurally all three neoplasms consisted of cells containing catecholamine granules. Prominent cytoplasmic crystalloids were present in all cases. The crystalloids were identified in routine histologic sections, demonstrated eosinophilia, and stained with periodic acid-Schiff, Giemsa, phloxine-tartrazine, and azan stains. Ultrastructurally the crystalloids were osmiophilic, often appeared as slender needles, were membrane bound, and demonstrated a periodicity of 9 nm. The crystalloids, unlike the catecholamine granules, were negative for catecholamine fluorescence. X-ray microanalysis, however, revealed the selective presence of chromium in both catecholamine granules and crystalloids.     

恶性小圆细胞肿瘤免疫组织化学及病理组织学分析

本文分析57例恶性小凶细胞肿瘤(MSRCT)免疫组化表型及病理形态。结果表明:兔抗鸡结蛋白及(或)兔抗人肌红蛋白可作为横纹肌肉瘤的标志;神经母细胞瘤、嗅神经母细胞瘤及原始外周神经外胚层瘤的免疫组化特征为NSE阳性,而Vim阴性;抗NSE抗血清特异性差,其他MSRCT亦可与之反应。尤文肉瘤Vim阳性,有些病例NSE阳性。未分化滑膜肉瘤Vim阳性;部分病例Ker及(或)EMA阳性,可有假阴性。LCA是恶性淋巴瘤特异性标记。α_1-ACT对MSRCT鉴别诊断无价值。     

Metastatic Melanoma: The Spectrum of Ultrastructural Morphology

The fine structure of 26 metastatic melanomas, including 13 pigmented and 13 amelanotic tumors, was studied to define ultrastructural criteria for diagnosis. Several important features in addition to melanosome granules were identified. Dendritic cytoplasmic processes were seen in 25 of the 26 cases, cell clusters formed by concentric aggregates of several cells and their processes were present in 18, and microvilli were found on cell surfaces in all cases. The cytoplasm was complex, containing numerous mitochondria, Golgi systems, endoplasmic reticulum, nonspecific filaments, and microtubules. Nuclear morphology was variable. Basement membranes and cell junctions including desmosomes were often encountered, and some melanomas shared features with Schwann cells, including complex membrane interdigitations. All tumors contained melanosomes, although the classic forms were frequently difficult to identify and abnormal variant forms often predominated. Knowledge of the variant melanosome morphology and an understanding of the other fine structural features of malignant melanocytes can help identify those cases that lack classic premelanosome granules.     

Metastatic Melanoma: The Spectrum of Ultrastructural Morphology

The fine structure of 26 metastatic melanomas, including 13 pigmented and 13 amelanotic tumors, was studied to define ultrastructural criteria for diagnosis. Several important features in addition to melanosome granules were identified. Dendritic cytoplasmic processes were seen in 25 of the 26 cases, cell clusters formed by concentric aggregates of several cells and their processes were present in 18, and microvilli were found on cell surfaces in all cases. The cytoplasm was complex, containing numerous mitochondria, Golgi systems, endoplasmic reticulum, nonspecific filaments, and microtubules. Nuclear morphology was variable. Basement membranes and cell junctions including desmosomes were often encountered, and some melanomas shared features with Schwann cells, including complex membrane interdigitations. All tumors contained melanosomes, although the classic forms were frequently difficult to identify and abnormal variant forms often predominated. Knowledge of the variant melanosome morphology and an understanding of the other fine structural features of malignant melanocytes can help identify those cases that lack classic premelanosome granules.     

Emperipolesis in a Case of Malignant Lymphoma: Electron Microscopic and Immunohistochemical Investigation

In the tissue sections of axillary lymph nodes surgically removed from a case of malignant lymphoma (non-Hodgkin's, diffuse, large cell type), many large cells were observed to contain lymphoma cells in their cytoplasm. From the findings of light microscopy in serial sections and electron microscopy, this phenomenon was confirmed to be “emperipolesis.” By immunohistochemistry, the large cells that contained lymphoma cells possessed most of the monocyte/macrophage markers, whereas the lymphoma cells revealed some B-cell markers, suggesting that they were of germinal center cell origin. In a survey of the literature, we found no report describing emperipolesis in the tissue sections of malignant lymphoma. Although the precise mechanisms and biological significance of emperipolesis in the present case are not fully understood, the existence of some interactions between macrophages and lymphoma cells is suggested.     

Emperipolesis in a Case of Malignant Lymphoma: Electron Microscopic and Immunohistochemical Investigation

In the tissue sections of axillary lymph nodes surgically removed from a case of malignant lymphoma (non-Hodgkin's, diffuse, large cell type), many large cells were observed to contain lymphoma cells in their cytoplasm. From the findings of light microscopy in serial sections and electron microscopy, this phenomenon was confirmed to be “emperipolesis.” By immunohistochemistry, the large cells that contained lymphoma cells possessed most of the monocyte/macrophage markers, whereas the lymphoma cells revealed some B-cell markers, suggesting that they were of germinal center cell origin. In a survey of the literature, we found no report describing emperipolesis in the tissue sections of malignant lymphoma. Although the precise mechanisms and biological significance of emperipolesis in the present case are not fully understood, the existence of some interactions between macrophages and lymphoma cells is suggested.     

Pancreatic PEComa: A Case Report with Ultrastructural Localization of HMB-45 within Melanosomes

PEComas (perivascular epithelioid cell tumors) represent a group of mesenchymal neoplasms showing characteristic morphologic, immunohistochemical, ultrastructural, and genetic features. These neoplasms are usually considered benign, being often well circumscribed by a thin capsule and showing scarce atypia. However, in some cases, they show local invasion and multiple metastases and cause the patient’s death. PEComas have been found in many locations, but only 7 cases have been described in the pancreas to date. Here, the authors report an additional case of this rare neoplasm and demonstrate the HMB-45 immunoreactivity of melanosomes or premelanosomes at the ultrastructural level.     

Nondifferentiated-Type Small Cell Sarcoma of Kidney in a Young Woman

A case of rapidly fatal small cell sarcoma of kidney in a young woman is described. Histologic, immunohistochemical, and ultrastructural studies demonstrated some features not reported previously in the literature, such as the arrangement of vimentin intermediate filaments in small irregular masses and the presence of various types of cytoplasmic projections. These findings, together with the observation of rare neoplastic elements with immunophenotypic and subcellular aspects of histiocytic and myofibroblastic differentiation, suggest that this tumor should be included in a group of small cell sarcomas of kidney lacking features of differentiation and should be considered a new variant occurring in adulthood.     

Sarcomatoid Renal Cell Carcinoma Metastatic to the Heart: Report of a Case

An unusual case of metastatic sarcomatoid renal cell carcinoma is presented. Fifteen months after nephrectomy for a typical clear cell carcinoma, a 63-year-old man presented with bilateral pleural effusions, cardiomegaly, and tamponade. A pericardial biopsy showed an anaplastic spindle cell tumor that was strongly keratin positive and showed desmosomes ultrastructurally. The patient died shortly thereafter, and the autopsy revealed massive tumor infiltration of the heart, pulmonary and adrenal metastases, and tumor nodules at the incision site of his nephrectomy. The differential diagnosis of sarcomatoid renal cell carcinoma is discussed.     

Sarcomatoid Renal Cell Carcinoma Metastatic to the Heart: Report of a Case

An unusual case of metastatic sarcomatoid renal cell carcinoma is presented. Fifteen months after nephrectomy for a typical clear cell carcinoma, a 63-year-old man presented with bilateral pleural effusions, cardiomegaly, and tamponade. A pericardial biopsy showed an anaplastic spindle cell tumor that was strongly keratin positive and showed desmosomes ultrastructurally. The patient died shortly thereafter, and the autopsy revealed massive tumor infiltration of the heart, pulmonary and adrenal metastases, and tumor nodules at the incision site of his nephrectomy. The differential diagnosis of sarcomatoid renal cell carcinoma is discussed.     

Divergent differentiation in malignant melanomas: a review

The aim of this review was to document and discuss diagnostic problems associated with divergent differentiation ('metaplastic change') in malignant melanomas, defined as the development in these tumours of morphologically, immunohistochemically and/or ultrastructurally recognizable non-melanocytic cell or tissue components. Types of divergent differentiation reported in malignant melanoma include: fibroblastic/myofibroblastic, Schwannian and perineurial, smooth muscle, rhabdomyosarcomatous, osteocartilaginous, ganglionic and ganglioneuroblastic, neuroendocrine and probable epithelial. Divergent differentiation is certainly a rare phenomenon and, when it occurs, can be missed by unwary pathologists and lead to diagnostic uncertainty. A carefully chosen immunohistochemical panel and the input of electron microscopy can help to clarify the nature of the cellular differentiation of these tumours and lead to a correct final diagnosis. The clinical significance of such aberrations is uncertain, nor are the underlying mechanisms as yet well defined.     

Micropapillary Carcinoma of the Breast with Necrosis-like Cell Death: A Case Report

A primary invasive micropapillary carcinoma of the breast in a 46-year-old woman is reported. Histologically, it was composed predominantly of papillary tumor cell clusters without fibrovascular cores, surrounded by a clear space. Tumor cells were positive for cytokeratin (CK) 7, estrogen receptor (ER), and progesterone receptor (PR), but negative for p53, CK 20, CD34, c-Erb-B2, CK5, epidermal growth factor receptor (EGFR), vimentin, and c-kit. MUC1 expression was found at the reversed apical membrane of neoplastic cell clusters. Accordingly, electron microscopy showed the lack of basement membrane and presence of microvilli at the basal surface of the tumor cells. Moreover, ultrastructural examination revealed single tumor cell death characterized by patchy condensations of chromatin throughout the nucleus. These nuclear alterations were associated with the occurrence of empty cytoplasmic vacuoles, conferring a necrosis-like phenotype to this cell death. Alternative programmed cell deaths are reviewed and their morphologic distinction is discussed.