Perinucleolar Halos Research Articles

Fumarate hydratase-deficient renal cell carcinoma: a single institution-based study of 29 patients by clinicopathological, immunohistochemical and genetic approaches

Fumarate hydratase (FH)-deficient renal cell carcinoma (RCC) is a renal neoplasm associated with FH loss, aggressive behaviour, and poor survival. We present a histopathological and immunohistochemical overview of FH-deficient RCC to infer significant features for its differential diagnosis. In this study, FH-deficient RCC tissue samples from patients who underwent surgical resection or biopsy at a single institution between July 1995 and August 2022 were reviewed by conventional haematoxylin and eosin staining, immunohistochemistry, and whole genome analyses. Twenty-nine FH-deficient RCC specimens were examined ​based on immunohistochemistry findings regarding FH and S-(2-succino)cysteine (2SC). The histopathological findings included conspicuous nucleoli with a perinucleolar halo, resembling viral inclusion, eosinophilic cytoplasm, papillary and tubular growth patterns, and lack of stromal foam cell collection. Some tumours showed desmoplastic stroma, tumour-infiltrating lymphocytes, and solid growth pattern. One tumour presented low-grade oncocytic-like histomorphology. Widespread negativity for CD10, keratin 7, keratin 20, anaplastic lymphoma kinase, and GATA3 were observed in 24 specimens. All samples were positive for paired box gene 8, and the level of alpha-methylacyl-CoA racemase expression was variable. Whole exome sequencing of 19 tumours revealed nonsynonymous mutations, including missense mutations, splice donors, splice acceptors, frameshifts, and deletions in 15 tumours. Eleven tumours showed novel mutations. In conclusion, results revealed generally unfavourable clinical presentations and outcomes with a diverse range of FH mutations. These findings, along with the histopathological and immunohistochemical features, can be used to guide diagnosis and treatment.

Fumarate hydratase-deficient renal cell carcinoma: an oncology care institutional experience.

Renal cell carcinoma (RCC) accounts for 2% of all cancer cases worldwide, and majority are sporadic. The latest World Health Organization (WHO) classification of renal cell tumors (fifth edition, 2022) has molecularly defined renal tumor entities, which includes fumarate hydratase (FH)-deficient RCC. FH-deficient RCC is an aggressive carcinoma caused by pathogenic alterations in FH gene, seen in 15% of patients with hereditary leiomyomatosis and renal cell cancer syndrome (HLRCC) syndrome. These tumors occur more frequently at a younger age and present at an advanced stage, carrying a dismal prognosis. We report a series of 10 cases of FH-deficient RCC. The mean age was 49.8 years, and all cases presented in advanced stages (III and IV). Morphologically, the cases had varied architectural patterns with characteristic eosinophilic macronucleoli and perinucleolar halo. On immunohistochemistry (IHC), all showed diffuse nucleo-cytoplasmic expression of S-(2-succino)-cysteine (2-SC), with loss of FH in seven cases. FH-deficient RCCs are aggressive neoplasms and can be diagnosed using specific IHC markers (FH and 2-SC). These patients should undergo germline testing for FH gene mutation, genetic counseling, and surveillance of family members.

Fumarate Hydratase-Deficient Leiomyoma of the Uterine Corpus: Comparative Morphologic Analysis of Protein-Deficient Tumors With and Without Pathogenic Germline Fumarate Hydratase Gene Mutations.

Deficiency of fumarate hydratase (FH) protein expression in uterine corpus leiomyomas may be attributable to either germline or somatic mutations of the FH gene, the former being definitional for the hereditary leiomyomatosis and renal cell cancer syndrome. The authors assess whether, using previously reported FH-associated morphologic features, FH protein-deficient uterine corpus leiomyomas associated with a pathogenic germline mutations of the FH gene (group 1) are distinguishable from FH protein-deficient uterine corpus leiomyomas without such mutations (and whose FH protein loss is presumed to be attributable to somatic/epigenetic inactivation or other unknown phenomena: group 2). Groups 1 and 2 were compared regarding a variety of clinicopathologic features, including 7 core "FH-associated" tumoral morphologic features: staghorn vasculature; alveolar-type edema; bizarre nuclei; chain-like tumor nuclei; hyaline cytoplasmic globules; prominent nucleoli, intranuclear inclusions, and perinucleolar halos; and prominent eosinophilic/fibrillary cytoplasm. Among 2418 patients diagnosed with uterine corpus leiomyoma during the study period, FH-associated morphologic features were reported in 1.5% (37 patients), and FH immunohistochemistry was performed in 29 (1.19%). Fourteen (48.27%) of the 29 patients showed FH protein deficiency by immunohistochemistry. Twelve patients underwent germline testing, of which 8 (66.7%) were classified as group 1 and 4 (33.3%) as group 2. FH protein-deficient tumors were larger (10.44 vs 4.08 cm, P = 0.01) and associated with younger patients (42.05 vs 47.97, P = 0.004) than 370 randomly selected uterine leiomyoma controls. Groups 1 and 2 showed no significant differences in patient age and tumor size. In group 1 tumors, the FH-associated morphologic features were generally present diffusely; all group 1 tumors displayed ≥5 FH-associated features, whereas all group 2 tumors displayed <5 FH-associated features (means 6.5 ± 0.53 vs 3.5 ± 1.00, P < 0.001). Notably, eosinophilic/fibrillary cytoplasm and alveolar-type edema were each significantly more prevalent in group 1 tumors than group 2 tumors (P = 0.018 for both). No single morphologic feature was found to be completely sensitive and specific in making the distinction between group 1 and 2 tumors. Our findings suggest that groups 1 and 2 are unlikely to be morphologically distinguishable by individual morphologic features. Whether there is a combination of features that can reliably make this distinction is unclear and will require additional studies with larger cohorts.

Diffuse Carbonic Anhydrase 9 and GATA3 Expression in Fumarate Hydratase Deficient Renal Cell Carcinoma - A Case Report and Immunoprofile Review.

Fumarate hydratase deficient renal cell carcinoma (FHRCC) can exhibit a heterogenous immunoprofile. In the present case, a solitary 10.5 cm mixed cystic and solid left kidney tumor showed various growth patterns, involving renal sinus adipose tissue and the renal pelvis. Tumor cells showed prominent nucleoli and perinucleolar halos. Aberrant diffuse (>90%), strong, and membranous carbonic anhydrase 9 and variable GATA3 expression were present. Diagnostic loss of fumarate hydratase expression and 2-succinyl cysteine overexpression (cytoplasmic and nuclear) were identified. Carbonic anhydrase 9 and GATA3 expression in FHRCC is rarely reported in the literature, and may cause misdiagnosis of clear cell RCC and/or urothelial carcinoma.

FH-deficient renal cell carcinoma expands the spectrum of renal papillary tumors

Das Fumarat-Hydratase(FH)-defiziente Nierenzellkarzinom (NZK) ist eine distinkte Entität, welche eine biallelische Inaktivierung des FH-Gens zeigt, die konsekutiv mit einem Expressions- bzw. Funktionsverlust des FH-Proteins einhergeht. Diese Alteration führt zu einer Akkumulation des Onkometaboliten Fumarat im Citratzyklus und vielfältigen Störungen des Zellhaushaltes und der DNA-Prozessierung. Das FH-defiziente NZK zeigt häufig ein morphologisch überlappendes Spektrum mit papillären NZK (Typ 2), wobei typischerweise ein Wechsel verschiedener Wachstumsmuster inkl. tubulozystischer, kribriformer und/oder solider Differenzierung zu beobachten ist. Eine typische, jedoch nicht spezifische morphologische Eigenschaft sind die prominenten eosinophilen, Viruseinschlußkörperchen-artigen Nukleolen mit perinukleolärem Halo. Der immunhistochemische Verlust der FH-Expression untermauert die Diagnose, kann in seltenen Fällen jedoch erhalten sein. Zumeist zeigen FH-defiziente NZK ein sehr aggressives biologisches Verhalten mit oftmalig primärer Metastasierung bei Diagnosestellung. Die initiale Beschreibung erfolgte als NZK in Assoziation mit dem Hereditären-Leiomyomatose-und-Nierenzellkarzinom(HLRCC)-Syndrom, welches zusätzlich kutane und uterine Leiomyome umfasst. Aktuelle Daten zeigen jedoch auch einen steigenden Anteil an sporadischen Fällen, sodass eine Unterscheidung (hereditär vs. sporadisch) angemessen erscheint. Bisher sind wenige, aber vielversprechende Daten bezüglich wirksamer systemischer therapeutischer Optionen beschrieben. Zusammenfassend ist eine korrekte Diagnose aufgrund des typischerweise biologisch aggressiven Verhaltens, gegebenenfalls vom Standard abweichender therapeutischer Optionen und möglichem Indikator einer hereditären Erkrankung von großer Bedeutung.

Hereditary leiomyomatosis and renal cell carcinoma syndrome-associated renal cell carcinoma: Morphological appraisal with a comprehensive review of differential diagnoses.

Hereditary leiomyomatosis and renal cell carcinoma (HLRCC) is an autosomal dominant syndrome wherein affected individuals are at risk for the development of cutaneous leiomyomas, early-onset multiple uterine leiomyomas, and an aggressive subtype of renal cell cancer. HLRCC is caused by germline mutations in the fumarate hydratase (FH) gene, which inactivates the enzyme and alters the function of the tricarboxylic acid/Krebs cycle. This article reviews the hitherto described morphologic features of HLRCC-associated renal cell carcinoma (RCC) and outlines the differential diagnosis and ancillary use of immunohistochemistry and molecular diagnostics for these tumors. The morphologic spectrum of HLRCC-associated RCC is wide and histologic features, including tumor cells with prominent nucleoli, perinucleolar halos, and multiple architectural patterns within the same tumor, which are suggestive of this diagnosis. FH immunohistochemistry in conjunction with genetic counseling and germline FH testing are the important parameters for detection of this entity. These kidney tumors warrant prompt treatment as even smaller sized lesions can demonstrate aggressive behavior and systemic oncologic treatment in metastatic disease should, if possible, be part of a clinical trial. Screening procedures in HLRCC families should preferably be evaluated in large cohorts.

Fumaratehydratase-deficient renal cell carcinoma: a clinicopathological and molecular study of 13 cases

AimsHereditary leiomyomatosis and renal cell carcinoma (HLRCC) is a newly recognised entity in the WHO 2016 classification defined as the germline mutation of FH gene. Fumaratehydratase-deficient renal cell carcinoma (FH-deficient...

Hereditary Leiomyomatosis and Renal Cell Carcinoma Syndrome (HLRCC): A Contemporary Review and Practical Discussion of the Differential Diagnosis for HLRCC-Associated Renal Cell Carcinoma.

Hereditary leiomyomatosis and renal cell carcinoma syndrome (HLRCC) is an uncommon disorder with germline-inactivating mutations in the fumarate hydratase ( FH) gene. The kidney cancers that develop in patients with HLRCC are often unilateral and solitary, with a potentially aggressive clinical course; morphologic identification of suspicious cases is of the utmost importance. To review classic morphologic features of HLRCC-associated renal cell carcinoma, the reported morphologic spectrum of these tumors and their mimics, and the evidence for use of immunohistochemistry and molecular testing in diagnosis of these tumors. University of Michigan cases and review of pertinent literature about HLRCC and the morphologic spectrum of HLRCC-associated renal cell carcinoma. Histologic features, such as prominent nucleoli with perinucleolar halos and multiple architectural patterns within one tumor, are suggestive of HLRCC-associated renal cell carcinoma. However, the morphologic spectrum is broad. Appropriate use of FH immunohistochemistry and referral to genetic counseling is important for detection of this syndrome.

Pattern multiplicity and fumarate hydratase (FH)/S-(2-succino)-cysteine (2SC) staining but not eosinophilic nucleoli with perinucleolar halos differentiate hereditary leiomyomatosis and renal cell carcinoma-associated renal cell carcinomas from kidney tumors without FH gene alteration

AbstractHereditary leiomyomatosis and renal cell carcinoma syndrome is characterized by an increased risk of agressive renal cell carcinoma, often of type 2 papillary histology, and is caused by FH germline mutations. A prominent eosinophilic macronucleolus with a perinucleolar clear halo is distinctive of hereditary leiomyomatosis and renal cell carcinoma syndrome-associated renal cell carcinoma according to the 2012 ISUP and 2016 WHO kidney tumor classification. From an immunohistochemistry perspective, tumors are often FH-negative and S-(2-succino)-cysteine (2SC) positive. We performed a pathology review of 24 renal tumors in 23 FH mutation carriers, and compared them to 12 type 2 papillary renal cell carcinomas from FH wild-type patients. Prominent eosinophilic nucleoli with perinucleolar halos were present in almost all FH-deficient renal cell carcinomas (23/24). Unexpectedly, they were also present in 58% of type 2 papillary renal cell carcinomas from wild-type patients. Renal cell carcinoma in mutation carriers displayed a complex architecture with multiple patterns, typically papillary, tubulopapillary, and tubulocystic, but also sarcomatoid and rhabdoid. Such pattern diversity was not seen in non-carriers. FH/2SC immunohistochemistry was informative as all hereditary leiomyomatosis and renal cell carcinoma-associated renal cell carcinomas were either FH− or 2SC+. For FH and 2SC immunohistochemistries taken separately, sensitivity of negative anti-FH immunohistochemistry was 87.5% and specificity was 100%. For positive anti-2SC immunohistochemistry, sensitivity, and specificity were 91.7% and 91.7%, respectively. All FH wild-type renal cell carcinoma were FH-positive, and all but one were 2SC-negative. In conclusion, multiplicity of architectural patterns, rhabdoid/sarcomatoid components and combined FH/2SC staining, but not prominent eosinophilic nucleoli with perinucleolar halos, differentiate hereditary leiomyomatosis and renal cell carcinoma-associated renal cell carcinoma from type 2 papillary renal cell carcinoma with efficient FH gene. Our findings are crucial in identifying who should be referred to Cancer Genetics clinics for genetic counseling and testing.

Leiomyoma with bizarre nuclei: a morphological, immunohistochemical and molecular analysis of 31 cases

Leiomyomas associated with hereditary leiomyomatosis and renal cell carcinoma syndrome and leiomyomas with bizarre nuclei often show overlapping morphological features, in particular cells with prominent eosinophilic nucleoli, perinucleolar halos, and eosinophilic cytoplasmic inclusions. Although hereditary leiomyomatosis and renal cell carcinoma syndrome is defined by fumarate hydratase (FH) germline mutations, resulting in S-(2-succino)-cysteine (2SC) formation, it is unknown whether leiomyomas with bizarre nuclei show similar alterations. In this study, we evaluated the morphology and FH/2SC immunoprofile of 31 leiomyomas with bizarre nuclei. DNA from tumor and normal tissues from 24 cases was subjected to massively parallel sequencing targeting 410 key cancer genes. Somatic genetic alterations were detected using state-of-the-art bioinformatics algorithms. No patient reported a personal history of renal neoplasia or cutaneous leiomyomas, but one had a family history of renal cell carcinoma while another had a family history of uterine leiomyomas. Aberrant FH/2SC expression was noted in 17 tumors (16 FH-negative/2SC-positive, 1 FH-positive/2SC-positive). On univariate analysis, staghorn vessels, eosinophilic cytoplasmic inclusions, diffuse distribution of prominent eosinophilic nucleoli with perinucleolar halos, and an ‘alveolar pattern of edema’ were associated with an abnormal immunoprofile, but only staghorn vessels remained significant on multivariate analysis. Massively parallel sequencing analysis (n=24) revealed that 13/14 tumors with aberrant FH/2SC immunoprofile harbored somatic FH somatic genetic alterations, including homozygous deletions (n=9), missense mutations coupled with loss of heterozygosity (n=3), and a splice site mutation (n=1), whereas no somatic FH mutations/deletions were found in tumors with normal immunoprofile (n=10; P<0.0001). Leiomyomas with bizarre nuclei with normal FH/2SC staining pattern more frequently harbored TP53 and/or RB1 alterations than those with aberrant FH/2SC immunoprofile (60 vs 14%; P=0.032). These data demonstrate that leiomyomas with bizarre nuclei are morphologically and genetically heterogeneous and that hereditary leiomyomatosis and renal cell carcinoma syndrome-related morphological features, abnormal FH/2SC staining, and somatic FH mutations/deletions can be seen in a subset of sporadic tumors.

Two Subtypes of Atypical Leiomyoma: Clinical, Histologic, and Molecular Analysis.

Atypical leiomyoma (ALM) is a rare variant of uterine smooth muscle tumors. Several recent studies have suggested that ALM has distinct, but also heterogenous, histologic and molecular features, yet little is known about the biology and histogenesis of ALM. Some have even postulated whether the atypical histologic features represent true atypia or simply degenerative changes. In this study, we analyzed the cytologic features of 60 ALM cases and found that ALM could be further divided into 2 subtypes, type I and type II, based primarily on nuclear features. Type I ALM showed round or oval nuclei, distinct and smooth nuclear membranes, prominent nucleoli with perinucleolar halos, and open coarse chromatin. Type II ALM showed elongated or spindled nuclei, irregular nuclear membranes, pinpoint or no nucleoli, and dark smudgy chromatin. There were also architectural differences between type I and type II ALM. Type I ALM often showed diffuse atypia within the tumor, whereas the atypia in type II ALM was patchy, surrounded by usual-type leiomyoma. The 2 subtypes also differed when we compared the immunohistochemical and molecular patterns. Type II tumors showed significantly higher rates of immunoreactivity for p16, p53, and HMGA2 and showed MED12 mutations more frequently than the type I counterparts. Our findings suggest that the type I and type II subtypes of ALM may arise from 2 different pathways. Type I tumors may be related to fumarate hydratase mutations, whereas type II ALM appear to arise in a existing usual-type leiomyomas.

Uterine smooth muscle tumors with features suggesting fumarate hydratase aberration: detailed morphologic analysis and correlation with S-(2-succino)-cysteine immunohistochemistry

Rare, sporadic uterine leiomyomas arise in the setting of severe metabolic aberration due to a somatic fumarate hydratase mutation. Germline mutations account for the hereditary leiomyomatosis and renal cell carcinoma syndrome, which predisposes for cutaneous and uterine leiomyomas and aggressive renal cell carcinomas. Altered fumarate hydratase leads to fumarate accumulation in affected cells with formation of S-(2-succino)-cysteine, which can be detected with the polyclonal antibody. High levels of these modified cysteine residues are found characteristically in fumarate hydratase-deficient cells but not in normal tissues or tumors unassociated with hereditary leiomyomatosis and renal cell carcinoma syndrome. We hypothesized that S-(2-succino)-cysteine-positive leiomyomas, indicating fumarate hydratase aberration, have morphologic features that differ from those without S-(2-succino)-cysteine positivity. Hematoxylin and eosin-stained slides of uterine smooth-muscle tumors were prospectively analyzed for features suggesting hereditary leiomyomatosis and renal cell carcinoma syndrome, such as prominent eosinophilic macronucleoli with perinucleolar halos, yielding nine cases. Germline genetic testing for fumarate hydratase mutations was performed in three cases. A detailed morphological analysis was undertaken, and S-(2-succino)-cysteine immunohistochemical analysis was performed with controls from a tissue microarray (leiomyomas (19), leiomyosarcomas (29), and endometrial stromal tumors (15)). Of the nine study cases, four had multiple uterine smooth muscle tumors. All cases had increased cellularity, staghorn vasculature, and fibrillary cytoplasm with pink globules. All cases had inclusion-like nucleoli with perinuclear halos (7 diffuse, 1 focal). All showed diffuse granular cytoplasmic labeling with the S-(2-succino)-cysteine antibody. Two of three tested patients had germline fumarate hydratase mutations. Only one leiomyoma from the tissue microarray controls was immunohistochemically positive, and it showed features similar to other immunohistochemically positive cases. Smooth-muscle tumors with fumarate hydratase aberration demonstrate morphological reproducibility across cases and S-(2-succino)-cysteine immuno-positivity. Although the features described are not specific for the germline fumarate hydratase mutation or the hereditary leiomyomatosis and renal cell carcinoma syndrome, their presence should suggest fumarate hydratase aberration. Identifying these cases is an important step in the diagnostic workup of patients with possible hereditary leiomyomatosis and renal cell carcinoma.

Morphologic and Molecular Characteristics of Uterine Leiomyomas in Hereditary Leiomyomatosis and Renal Cancer (HLRCC) Syndrome

Hereditary leiomyomatosis and renal cell cancer (HLRCC) is a hereditary cancer syndrome in which affected individuals are predisposed to the development of multiple leiomyomas of the skin and uterus and aggressive forms of kidney cancer. Affected individuals harbor a germline heterozygous loss-of-function mutation of the fumarate hydratase (FH) gene. Uterine leiomyomas are present in up to 77% of women with this syndrome. Previous studies have shown that inactivation of the FH gene is unusual for nonsyndromic leiomyomas. Therefore, it might be possible to distinguish 2 genetic groups of smooth muscle tumors: the most common group of sporadic uterine leiomyomas without FH gene inactivation and the more unusual group of HLRCC leiomyomas in patients who harbor a germline mutation of FH, although the exact prevalence of hereditary HLRCC is unknown. We reviewed the clinical, morphologic, and genotypic features of uterine leiomyomas in 19 HLRCC patients with FH germline mutations. Patients with HLRCC syndrome were younger in age compared with those with regular leiomyomata. DNA was extracted by microdissection, and analysis of loss of heterozygosity (LOH) at 1q43 was performed. Uterine leiomyomas in HLRCC have young age of onset and are multiple, with size ranging from 1 to 8 cm. Histopathologically, HLRCC leiomyomas frequently had increased cellularity, multinucleated cells, and atypia. All cases showed tumor nuclei with large orangeophilic nucleoli surrounded by a perinucleolar halo similar to the changes found in HLRCC. Occasional mitoses were found in 3 cases; however, the tumors did not fulfill the criteria for malignancy. Our study also showed that LOH at 1q43 was frequent in HLRCC leiomyomas (8/10 cases), similarly to what has been previously found in renal cell carcinomas from HLRCC patients. LOH is considered to be the second hit that inactivates the FH gene. We conclude that uterine leiomyomas associated with HLRCC syndrome have characteristic morphologic features. Both, uterine leiomyomas and renal cell carcinoma share some morphologic nuclear changes and genotypic features in HLRCC patients. The specific morphologic features of the uterine leiomyomas that we describe may help in the identification of patients who may be part of the hereditary syndrome.

Morphologic Features of Uterine Leiomyomas Associated With Hereditary Leiomyomatosis and Renal Cell Carcinoma Syndrome

Patients with hereditary leiomyomatosis and renal cell carcinoma (HLRCC) syndrome are prone to develop smooth muscle tumors of the uterus and skin and also renal carcinomas. The morphologic features of renal tumors that arise in the setting of HLRCC are well described, the hallmark feature being the presence of prominent eosinophilic nucleoli surrounded by a clear halo. Renal tumors associated with HLRCC are aggressive and often present late with high-stage disease. Early detection of patients with HLRCC could lead to surveillance for renal carcinomas. Women with HLRCC often present at a young age with uterine leiomyomas and frequently undergo hysterectomy as a result. HLRCC associated uterine leiomyomas show nuclear features similar to those described in HLRCC associated renal tumors. Therefore, presence of these nuclear features in uterine smooth muscle tumors may aid in early detection of HLRCC, resulting in surveillance for renal carcinoma. We present a case of a 32-year-old woman who underwent hysterectomy for uterine fibroids and subsequently presented 5 years later with high-stage renal carcinoma. Histologic evaluation of uterine leiomyomas and renal carcinoma revealed identical nuclear features, that is, prominent nucleoli with perinucleolar halos, raising the possibility of HLRCC. Subsequent testing confirmed a fumarate hydratase mutation. The presence of above-described nuclear features in uterine leiomyomas should raise the possibility of HLRCC.

Sebaceous carcinoma of the eyelids: Thirty cases from Japan

Sebaceous carcinoma of the eyelids is rare in Western countries but not uncommon in Asian countries. Diagnosis is difficult both clinically and histologically. Thirty cases of sebaceous carcinoma of the eyelids treated at Tokyo Medical University Hospital were reviewed to elicit characteristic features of pathological findings. The tumor cells were infiltrating in a lobular pattern that consisted mainly of large atypical germinative cells. Sebocytes seen in the lobules had conspicuous nucleolus associated with perinucleolar halo. In 17 cases (57%) there was foamy histiocyte infiltration in and around the tumor nests. Sebaceous duct differentiation, namely holocrine secretion indicating a specific type of coagulation necrosis maintaining a cellular framework or maintaining a bubbly cytoplasm associated with nuclear debris in the periphery, was seen in 24 cases (80%). Although unequivocal squamous differentiation was limited to only 11 carcinomas, scattered individual necrosis with nuclear debris in the background of germinative cells appeared in 29 cases (96.7%). Expression of epithelial membrane antigen, perilipin and adipophilin were detected in all cases. In conclusion, to detect sebaceous differentiation in sebaceous carcinoma, it would be helpful to focus on holocrine secretion, squamous differentiation and foamy macrophage infiltration, and to utilize immunohistochemistry involving anti-perilipin and anti-adipophilin stain.

Intranucleolar visualization of nucleic acids and acidic proteins in inhibited and reactivated pea cotyledonary buds

Nuclease-colloidal gold complexes and silver staining were used to visualize intranucleolar nucleic acids and argyrophilic proteins of the nucleolar organizers in bud cotyledonary cells ofPisum sativum. In the G0–1 inhibited bud, a few RNA molecules were detected in the fibrillar component and in the unique fibrillar centre, close to the boundary with the fibrillar component of the nucleolus. DNA was present in the fibrillar component, in the fibrillar centre and in a few fibres crossing the perinucleolar halo. The acidic proteins were localized at the periphery of the fibrillar component but they were also present in the unique fibrillar centre. In the reactivated bud, RNA was particularly concentrated in the granular component and along fibres crossing the perinucleolar halo; a few RNA molecules were also detected at the boundary between the small fibrillar centres and the fibrillar component. DNA was localized in the same nucleolar component as in the inhibited bud, but it was distributed between several fibrillar centres. Acidic proteins coated these DNA loci. In the inhibited and reactivated bud connections between nucleolar DNA containing structures were displayed. The data are discussed in relation to the present knowledge of the functional architecture of the nucleolus.

Nuclear differentiation during the course of syncytiogenesis in mouse trophoblast

Several morphological and quantitative changes of the nuclear components were observed during the differentiation of pre-syncytial trophoblast into mature syncytial trophoblast. Nuclear volume first increased, then markedly decreased. The area of condensed chromatin augmented while nucleolar volume was reduced. A peculiar structure, here called “perinucleolar halo,” was found to outline all nucleoli in mature syncytial nuclei. Therefore, in mouse trophoblast, a characteristic course of differentiation of the cell nucleus as an organelle is induced by cell fusion. It is suggested that a cytoplasmic organelle, “the glomerular body,” is associated with the nuclear differentiation.

Interphase Nuclei from Lemon-Fruit Tissue

Interphase nuclei were examined in living epidermal cells of intact juice sacs from mature lemon fruits. A definitive halo enveloping each nucleolus was observed. Evidence is presented which substantiates this perinucleolar halo as a definitive nuclear region and not as an optical ring resulting from diffraction about the perimeter of a disk. Interphase nuclei were also examined in mature non-growing and excised lemon fruit tissue growing in vitro. Definitive refractile bodies become evident in the nucleoli of the growing tissue; these manifest distinct birefringence under polarizing microscopy. The presence of anisotropic material in nucleoli of interphase nuclei of apical buds from lemon trees, in stem and root tissues from germinating lemon seedlings, and in vesicle stalks from freshly picked mature lemon fruits shows that the birefringent bodies in the nucleoli of the excised fruit tissue are not abnormal characteristics of cells grown in vitro or of aging processes. Anisotropic nucleolar material was also observed in germinating seedlings of plant genera other than Citrus, thus showing that nucleolar birefringence is not peculiar to Citrus.