Ultrastructural studies of cells in body cavity effusions

Transmission electron microscopic examination of benign (16 cases) and malignant (2 cases) mesothelial cells and metastatic carcinoma (10 cases) was performed. These studies showed long, slender, branching and bushy microvilli with high length-to-diameter ratios to be the most important distinguishing features of the mesothelial cells. Cytoplasmic intermediate filaments were present in all mesothelial cells as well as in carcinoma cells. The mesothelial cells showed an absence of mucin vacuoles, intracellular lumens and luminal tight junctions, which are seen in adenocarcinoma cells. The pinocytotic vesicles were found to be more numerous in the mesothelial cells. Lipid vacuoles, lysosomes, Golgi apparatus and intercellular lumens appeared to be variably present in all mesothelial and carcinoma cells. The methodology is discussed and pertinent literature reviewed.     

DNA assessment in thin sections of lymphomas by densitometric and stereological methods: comparison with imprint and flow cytometric results

The nuclear DNA content was estimated in 2 microns sections of 18 lymphoma cases by two methods: (1) Feulgen densitometry using QTM 900 with correction by Bins' procedure which allows size-independent DNA distributions; (2) stereological unfolding as proposed by Cruz-Orive giving sphere-size distributions. A general correlation was found between results and DNA measurements obtained by imprint and flow cytometric techniques in the same specimens. When histologic DNA profiles were compared to cytologic histograms, a high correlation was found between the distribution of ploidy classes by correspondence analysis. However two highly proliferating lymphomas were erroneously classified as aneuploid. Conversely, sphere-size distributions allowed the identification of the majority of aneuploid lymphomas but failed to recognize proliferating ones. It appears that when cytologic specimens are not available, densitometric studies on sections may provide valuable information on DNA content, with complementary data obtained from stereological procedures.     

Specific tumor markers in diagnostic cytology. Immunoperoxidase studies of carcinoembryonic antigen, lysozyme and other tissue antigens in effusions, washes and aspirates

The immunoperoxidase technique was used to identify specific tumor markers in exfoliated cells in fine needle aspirates and body fluids. Carcinoembryonic antigen (CEA) and lysozyme staining was evaluated in cytocentrifuge preparations from 42 malignant effusions and aspirates and 16 benign effusions. Reactive mesothelial cells were negative for CEA and lysozyme or showed faint peripheral cytoplasmic staining. Malignant cells from 50% of the adenocarcinomas studied were positive for CEA. All tumors studied were negative for lysozyme. These staining patterns are helpful in the differential diagnosis of reactive mesothelial and adenocarcinoma cells, a frequent diagnostic dilemma. Moreover, demonstration of specific tumor antigens (e.g., prostatic acid phosphatase, calcitonin and immunoglobulin) helped define the origin of metastatic malignancy in selected cases. Estrogen receptor activity was also identified in tumor cells using this technique. Immunoperoxidase was helpful in the evaluation of malignant cytologic specimens from patients with more than one tumor. Interpretation of staining patterns is discussed, with reference to the limitations of the technique. Immunoperoxidase methods maintain cytologic detail, are readily adaptable to diagnostic cytology and increase the specificity of cytologic diagnosis.     

Lower proliferation rate in metastatic effusion mesothelial cells than in benign effusions

OBJECTIVE: To determine the proliferation rates of mesothelial cells in metastatic and benign effusions. STUDY DESIGN: Immunohistochemistry was performed on formalin-fixed pellets from 16 malignant and 9 benign clinical effusions. Dual staining with antibodies against Ki-67 (MIB-1) and desmin was applied to all effusions to differentiate between benign mesothelial cells and malignant cells, and the proportions of desmin+/Ki-67+ and desmin+/Ki-67- cells were calculated. RESULTS: In 7 malignant effusions no proliferating mesothelial cells were found, whereas some rate of proliferation could always be demonstrated in mesothelial cells in the benign effusions. Further, the median proportions of proliferating cells, malignant 2% vs. benign 11%, differed significantly. CONCLUSIONS: To our knowledge this finding has not been previously described, and it may have implications for both cytologic diagnosis and the understanding of tumor biology and the interaction between tumor cells and mesothelial cells.     

Peritoneal washings in ovarian tumors. Potential sources of error in cytologic diagnosis

Peritoneal washings were performed on 48 patients with suspected or known ovarian carcinoma. The procedure was part of the initial surgical staging in 27 patients with presumed stage I and II ovarian cancer and was performed during second-look operations in 21 other cases with proven ovarian malignancy. This paper presents the microscopic features of the washings, with particular emphasis on the cytologic differentiation between benign and malignant findings outside of the ovary. Thirty-four cases showed benign or reactive mesothelial cells and no evidence of peritoneal disease. The washings of six patient showed malignant cells, which were confirmed histologically. Notable atypia that mimicked ovarian carcinoma was found in eight patients who had benign or borderline lesions. These findings included papillary and glandlike epithelial structures, with varying degrees of cellular atypia and psammoma bodies. The histologic counterparts of these atypicalities were Müllerian inclusions, mesothelial proliferations and borderline serous tumors. The differential diagnosis between these entities is essential because false-positive cytologic diagnoses may alter postoperative treatment in some patients.     

Comparison of cytologic and acridine-orange flow-cytometric detection of malignant cells in human body cavity fluids

Flow cytometrically (FCM) derived DNA and RNA profiles were studied in acridine orange (AO)-stained body cavity fluid (BCF) specimens obtained from 78 patients with various solid tissue and hematologic malignancies. The ploidy (DNA index), RNA content (RNA index), proliferative activity (% S + G2M) and DNA and RNA scattergram patterns were tested "double-blind" against the cytologic scoring of specimens as malignant, benign or reactive. It was determined that expression of an "abnormal" RNA index (greater than or equal to 2.8) and an elevated proliferative activity (% S + G2M greater than or equal to 7.4) was dependent on the presence of malignancy; 21 of 22 specimens having those abnormal indices had DNA aneuploidy and were cytologically scored as positive. The AO FCM sensitivity and specificity for detecting malignant cells (when measured against cytology scoring) were 61% and 90%, respectively, using the "abnormal" RNA index and % S + G2M cut-offs together with the cellular DNA aneuploidy marker. By supplementing the cytologic scoring with AO FCM DNA and RNA features, the sensitivity for detecting malignant cells was 94%, as compared to 72% for cytology alone. Two specimens gave false-positive FCM results: a tuberculous effusion with a tetraploid subpopulation and a reactive mesothelial proliferation that was diploid and negative cytologically. Scoring for malignancy based on the visual pattern of the DNA and RNA FCM scattergrams, while showing good correlation for aneuploid specimens, in some cases failed to identify diploid disease. The results demonstrate the usefulness of FCM DNA and RNA analysis for supplementing cytologic examination of BCF specimens for the purpose of detecting malignant cells.(ABSTRACT TRUNCATED AT 250 WORDS)     

An Electron Microscopic Study of the Ductuli Efferentes and Rete Testis of the Guinea Pig

The ductuli efferentes and rete testis of the guinea pig were isolated by micro dissection, fixed in cold buffered osmium tetroxide, and sectioned for examination with the light and electron microscopes. Proximal and distal segments of the ductuli efferentes were identified and their respective cytological organizations characterized. The cytological components of the rete testis are briefly described and figured. Non-ciliated and ciliated cells are found in both segments of the ductuli efferentes. The non-ciliated cells have a microvillous border, mitochondria, a Golgi complex, an ubiquitous endoplasmic reticulum, and numerous cytoplasmic vacuoles. The ciliated cells contain more mitochondria, an endoplasmic reticulum with a relatively sparse distribution, and few, if any, cytoplasmic vacuoles. A regional difference exists in proximal and distal segments based on the distribution, size, number, and electron opacity of the cytoplasmic vacuoles. Attention was paid to the disposition of the endoplasmic reticulum and its relation to the system of cytoplasmic vacuoles. These findings are interpreted as suggesting that the continuity of the vacuolar system with elements of the endoplasmic reticulum represents a pathway for transfer of large quantities of fluid, an activity which has long been ascribed to the epithelium of the ductuli efferentes. Periductular capillaries possess pore-like apertures in their endothelia similar to those in other tissues known to engage in fluid transfer.     

Cytodiagnosis of classic lobular carcinoma and its variants.

The well-known cytologic features of lobular carcinoma traditionally consist of modest cellularity and small, atypical cells lying singly or in small groups. However, lobular carcinoma is a common pitfall in the cytodiagnosis of breast lesions. Knowledge of its varied histologic appearance can help to prevent diagnostic difficulties. Among 55 consecutive cases of breast needle aspirates with histologic follow-up, 9 lobular carcinomas were identified. The surgical material was examined for the following histologic variants: (1) classic, (2) solid, (3) alveolar, and (4) mixed; it was correlated with the cytologic findings. Pure, classic lesions were the most likely cause of false-negative diagnoses. Two of nine lobular carcinomas were diagnosed as benign due to scant cellularity and cell smallness. Four of nine were cytologically misclassified as ductal type due to more abundant cellularity and larger cells. This could be attributed to the predominant alveolar or solid patterns present in three cases. Only three of nine were accurately classified as lobular carcinoma, and all had a significant classic histologic element. Another important feature that is highly suggestive of lobular carcinoma is the presence of cytoplasmic vacuoles. They were overlooked in three of four cases. This study suggested that the traditional cytologic features of lobular carcinoma are present only in tumors with a predominantly classic histologic pattern. Awareness of the variant patterns and their cytologic features, including more abundant cellularity, larger cells and clusters, and cytoplasmic vacuoles, will aid in correct classification.     

Diagnostic utility of GLUT-1 expression in the cytologic evaluation of serous fluids

OBJECTIVE: To evaluate the extent to which adenocarcinomas in body cavity fluids express GLUT-1 in comparison to currently available markers for adenocarcinomas. STUDY DESIGN: Archival paraffin-embedded cell blocks of serous fluids from 25 cases of benign effusions containing reactive mesothelial cells and 39 cases of malignant effusions with metastatic adenocarcinoma (11 ovarian, 11 pulmonary, 9 gastrointestinal and 8 breast) were retrieved from the surgical pathology files. All cases were stained with antibodies for GLUT-1, Ber-Ep4, B72.3 and CEA. Positive staining was defined as distinct linear membrane staining for GLUT-1 and Ber-EP4, cytoplasmic staining for CEA, and cytoplasmic or membrane staining for B72.3. Strong staining in at least 10% of the tumor cells was required in order to consider the case positive for the particular marker. RESULTS: GLUT-1 was expressed in 72% (28 of 39) of cases of malignant effusions: 100% (11 of 11) from the ovary, 91% (10 of 11) from the lung, 67% (6 of 9) from the gastrointestinal tract and 12% (1 of 8) from the breast. None (0 of 25) of the benign effusions expressed GLUT-1. Malignant effusions expressed CEA in 74% (29 of 39), Ber-Ep4 in 85% (33 of 39), and B72.3 in 62% (24 of 39). Benign effusions expressed CEA in 3 cases and B72.3 in 2 cases. CONCLUSION: GLUT-1 is a useful marker that can be applied to cytologic specimens. It can be used as a reliable component of an antibody panel to distinguish reactive mesothelial cells from metastatic adenocarcinoma in particular adenocarcinomas of body cavity effusions, in particular adenocarcinomas of ovarian and pulmonary origin.     

Cytologic criteria of cystic papillary carcinoma of the thyroid

OBJECTIVE: To establish differential cytologic criteria between benign and malignant thyroid cysts. STUDY DESIGN: The study was a retrospective, transverse, analytic, comparative one of 3 groups of patients with nonfunctional thyroid nodules subjected to fine needle aspiration biopsy (FNAB) and surgical resection of the lesions, with histologic study as the diagnostic gold standard. Fifteen cases of cystic papillary carcinomas (group 1) with initial false negative diagnoses, 42 goiters accompanied by cystic degeneration (group 2) and 15 noncystic papillary carcinomas (group 3) were studied. Independent variables were age and sex; dependent variables were the presence of tridimensional fragments, papillae, anisonucleosis, nuclear bars, pseudoinclusions, powdery chromatin, cytoplasmic vacuoles, metaplastic cytoplasm, psammoma bodies, autolysis, multinucleated giant cells, spindle cells, colloid, monolayered laminae and macrophages in FNAB specimens. Statistical analysis was performed by central tendency measures and the chi 2 test. RESULTS: The chi 2 test revealed a statistically significant difference between group 2 and the groups with papillary carcinoma based on the presence of tridimensional fragments, anisonucleosis, nuclear bars, pseudoinclusions, powdery chromatin, cytoplasmic vacuoles, metaplastic cytoplasm and autolysis. CONCLUSION: The above cytologic characteristics must be searched for systematically in the FNAB of every cystic lesion of the thyroid to rule out the presence of cystic papillary thyroid carcinoma and to decrease the rate of false negative results.     

Cytologic, cytochemical, immunocytochemical and ultrastructural diagnosis of a sacrococcygeal chordoma in a fine needle aspiration biopsy specimen

The cytologic, cytochemical, immunocytochemical and ultrastructural findings on the aspirated material are presented for the case of a 57-year-old man with sacrococcygeal chordoma diagnosed by fine needle aspiration biopsy. Cytologically, two types of cellular elements were differentiated: medium-sized cells with few cytoplasmic vacuoles and classic physaliferous cells. Both types showed marked cytoplasmic positivity for keratin and S-100 protein; the absence of nuclear positivity in the physaliferous cells was notable. Ultrastructural study demonstrated the existence of true intracytoplasmic vacuoles and frequent rough endoplasmic reticulum-mitochondria complexes. The cytologic differential diagnosis with chondrosarcoma, myxoid liposarcoma, ependymoma and metastases of mucosecretory carcinomas is reviewed.     

Clinical and cytologic features of papillary neoplasms of the breast

OBJECTIVE: To compare the cytologic features benign and malignant papillary breast lesions. STUDY DESIGN: We reviewed the clinical and cytologic features in 29 cases of intraductal papilloma and 26 cases of atypical papilloma or papillary carcinoma that had been diagnosed by histologic examination. The diameter of the mass was examined as a clinical feature. The cytologic features evaluated were as follows: bloody background, row of tall columnar cells, naked bipolar nuclei, hemosiderin-laden macrophages, myoepithelial cells, single scattered atypical cells, cellularity, nuclear atypia, nuclear grade, apocrine metaplasia, eosinophilic cytoplasmic granules, papillary clusters, small papillae, cell balls and large sheets. RESULTS: Of the features evaluated, the diameter of the mass, naked bipolar nuclei and cell balls differed significantly between benign and atypical or malignant papillary neoplasms. The average diameter of a benign papillary neoplasm was 1.8 cm, and that of an atypical or malignant papillary neoplasm was 2.2 cm (p = 0.042). Naked bipolar nuclei were found in 27 cases of benign papillary neoplasm (93.1%) versus 19 cases of atypical or malignant papillary neoplasm (73.1%) (p = 0.050). Cell balls were found in 14 (48.3%) and 21 (80.8%) cases, respectively (p = 0.012). All 6 cases in which cell balls were present and naked bipolar nuclei were absent proved to be atypical or malignant papillary neoplasms. Of 17 cases in which cell balls were absent and naked bipolar nuclei present, 13 (76.5%) were benign papillary neoplasms. CONCLUSION: Most cytologic features overlapped in benign and atypical or malignant papillary neoplasms. Although they were not pathognomonic, naked bipolar nuclei and cell balls were cytologic features that differed significantly between benign and atypical or malignant papillary neoplasms. When papillary neoplasms of the breast are suspected in a cytologic smear, the combination of clinical examination, mammography and cytologic features should be considered to make the correct diagnosis.     

Ultrastructure of pleural mesothelioma and pulmonary adenocarcinoma in malignant effusions as compared with reactive mesothelial cells.

OBJECTIVE: To determine the ultrastructural features of diffuse malignant pleural mesothelioma cells in cytologic specimens from pleural effusions. STUDY DESIGN: We retrospectively studied 35 pleural effusions: 12 diffuse malignant pleural mesotheliomas (8 epithelial type, 4 biphasic type), 12 pulmonary adenocarcinomas and 11 cases of reactive mesothelial cells. RESULTS: In the cytoplasm, reactive and malignant mesothelial cells had more-abundant intermediate filaments (P < .05, P < .01) and fewer free ribosomes (P < .001, P < .001) than adenocarcinoma cells. Reactive mesothelial cells had fewer mitochondria than mesothelioma cells (P < .05). Mesothelioma cells had longer, thinner microvilli on the cell surfaces (P < .001); length/diameter ratios of microvilli were 19.1 +/- 7.0 (mesothelioma) vs. 9.1 +/- 2.2 (adenocarcinoma) and 9.2 +/- 2.4 (mesothelial cells). Giant intercellular junctions (desmosomes or desmosomelike structures > 1 micron in length) were found in eight cases of mesothelioma. Core filaments or rootlets in microvilli were present in two cases of adenocarcinoma. CONCLUSION: Because cytologic specimens from pleural effusions were easy to obtain, we think ultrastructural cytology is useful in distinguishing mesothelioma from adenocarcinoma and benign effusions.     

Inhibition by insulin of the physiological autophagic breakdown of cell organelles

By using electron microscopic morphometry it was found that the fractional volume of autophagic vacuoles in the cytoplasm of liver cells decreased rapidly after administering 5 units insulin per kg body weight to otherwise untreated rats. From the decay which appears to follow first order kinetics a half-life of 9 min was found for the compartment of autophagic vacuoles. The rates of autophagic breakdown calculated were different for the different cytoplasmic components, indicating that selecting mechanisms are involved in the process of segregation which is the first step in autophagy.     

Logistic regression analysis of low grade spindle cell lesions. A cytologic study

OBJECTIVE: To identify key diagnostic cytologic criteria for various low grade spindle cell lesions. STUDY DESIGN: We reviewed 20 synovial sarcomas, 18 benign neural tumors, 10 reparative lesions, 24 other benign and 27 additional malignant low grade spindle cell lesions. All specimens were coded as to the presence or absence of the following variables: high cellularity, tissue fragments, tissue culture appearance, epithelial fragments, vessel fragments, vascular arcades, fibrillar ground substance, myxoid background, microcystic areas, parallel arrangement of nuclei, naked nuclei, single cells, binucleate cells, multinucleate cells, long filamentous cells, short spindle cells, stellate cells, lipoblasts, nuclear pleomorphism, nuclei with pointed ends, comma/fishhook nuclei, cigar-shaped nuclei, ovoid/round nuclei, small nucleoli, large nucleoli, mitotic figures, intranuclear vacuoles and background histiocytes. A logistic regression analysis was performed to identify the variables predictive of malignant lesions, specifically synovial sarcomas, benign neural tumors and reparative lesions. RESULTS: Statistical analysis selected high cellularity, short spindle cells, small nucleoli and absence of tissue culture appearance as the main criteria for malignant neoplasms. Tissue fragments and high cellularity were selected as the primary criteria and absence of long filamentous cells and of myxoid background as the secondary criteria for synovial sarcomas. It selected fibrillar ground substance and absence of ovoid/round nuclei as the key criteria for benign neural tumors. The presence of a tissue culture appearance was the major criterion for reparative lesions. CONCLUSION: There are many previously described cytologic criteria, but we found that when subjected to statistical analysis, only a few features were significant in the evaluation of low grade spindle cell lesions.     

Expression of matrix metalloproteinases-2 and -9 by cells isolated from the peritoneal fluid of women with ovarian carcinoma

OBJECTIVE: To investigate the level of expression of matrix metalloproteinases (MMP)-2 and -9 by cells isolated from the peritoneal fluid of women with ovarian carcinoma. STUDY DESIGN: Tumor tissue specimens and cells isolated from peritoneal fluid from 20 patients with epithelial ovarian carcinoma were examined for MMP-2 and -9 expression using immunostaining. Six benign peritoneal effusions containing mesothelial cells were also included in the study. RESULTS: Expression of both MMP-2 and -9 was noted in cancer cells in peritoneal fluid of all cases studied. Peritoneal fluid cancer cells showed increased expression of both MMP-2 and -9 relative to mesothelial cell expression of these MMPs. Positive immunoreactivity of these MMPs in primary tumor tissues was confirmed by immunohistochemistry. CONCLUSION: Our findings suggest that both MMP-2 and -9 are frequently overexpressed in ovarian cancer cells disseminated in the peritoneal cavity and that determination of cellular MMP-2 and -9 expression could be useful in distinguishing cancer cells from mesothelial cells in peritoneal fluid cytologic specimens from women with ovarian epithelial carcinoma.     

Immunohistochemical study of lysozyme, alpha 1-anti-chymotrypsin, tissue polypeptide antigen, keratin and carcinoembryonic antigen in effusion sediments

The cellular sediments of 42 malignant and 16 benign effusions (58 cases) were studied using the immunoperoxidase technique. Serial sections of formalin-fixed, paraffin-embedded residual sediments of effusions, sent for routine cytologic examination, were studied by commercially available polyclonal antisera against lysozyme, alpha 1-anti-trypsin, alpha 1-anti-chymotrypsin, tissue polypeptide antigen (TPA), a wide-spectrum anti-keratin, carcinoembryonic antigen (CEA) and, in single cases, thyroglobulin and prostate-specific antigen. A final definite diagnosis from histologic study of biopsy or autopsy specimens was known in all cases. All carcinomas, the mesotheliomas and the reactive mesothelial cells showed a positive reaction for TPA and, partly, the wide-spectrum keratin. Lysozyme could be demonstrated in the cells of the one proven malignant fibrous histiocytoma; all malignant epithelial cells were negative. Alpha 1-anti-chymotrypsin and alpha 1-anti-trypsin showed similar reactions: they were often positive in carcinoma cells of the breast, the bronchial system and the pancreas, in contrast to a mostly negative reaction in carcinomas of the stomach and ovary. CEA showed considerable differences; it was always negative in benign and malignant mesothelial proliferations but mostly positive in carcinomas of the stomach, pancreas and bronchial system. It was only positive in less than 20% of the carcinomas of the breast and always negative in the proven malignant effusions of primary carcinomas of the ovary and prostate. Studying a combination of several tumor markers is possible in serial paraffin-embedded sections and may be a valuable criterion in the cytologic diagnosis of effusions.     

Electron microscopy of vesicular-arbuscular mycorrhizae of yellow poplar. II. Intracellular hyphae and vesicles.

Intracellular hyphae and vesicles in mycorrhizal roots of yellow poplar were examined by electron microscopy. An investing layer of host wall material and cytoplasm enclosed the endophyte within the cells. Young developing hyphae contained abundant cytoplasm and few vacuoles. As hyphae matured, they became highly vacuolated and accumulated carbohydrate (glycogen) and lipid reserves. Mature vesicles were engorged with lipid droplets, possessed a trilaminate wall and were also enclosed by host wall material and cytoplasm. Compared with uninfected cells, infected cortical cells showed an increase in cytoplasmic volume, enlarged nuclei, and a reduction of starch reserves. Host nuclei were always proximal to the hyphae during hyphal development and deterioration. While other cytoplasmic components of infected and uninfected cells were comparable large electron-dense bodies occurred in vacuoles of most cells containing hyphae. Deterioration of intracellular hyphae occurred throughout the samples examined. Septa separated functional and degenerating portions of the hyphae. Hyphal deterioration involved degeneration and ultimate disappearance of fungal cytoplasm as well as collapse of hyphal walls. Based on these observations, the authors hypothesize that deterioration of the endophyte may release significant quantities of mineral nutrients, via hyphal contents, which are absorbed by the host.     

An unusual cytologic presentation of mesothelioma in serous effusions

Three cases of diffuse malignant mesothelioma in which samples of pleural fluid showed an unusual cytologic picture are presented. Instead of cells of an obvious mesothelial type forming organized clusters, the smears were dominated by foamy macrophage-like cells, with or without certain nuclear features suggesting malignancy. It is suggested that these cells were derived from neoplastic mesothelial cells by a process of differentiation.     

The Harderian gland of the Cheesman's gerbil (Gerbillus cheesmani ) of the Kuwaiti desert

The Harderian gland is a large orbital structure. Several functions have been ascribed to the gland such as lubrication of the eye, a source of pheromones, thermoregulartory lipids and photoprotective secretions and a part of the retinal-pineal axis. In the present study, the Harderian gland of the Cheesman's gerbil, Gerbillus cheesmani, is described for the first time. The gland is located around the posterior portion of the eyeball. The gland is compound tubular, surrounded by a thin connective tissue capsule. Only one secretory epithelial cell type was recognized, characterized by the presence of lipid vacuoles and cytoplasmic slashes in high numbers; the former being more concentrated towards the apical part while the latter being more concentrated towards the central and basal parts. Some of the cytoplasmic slashes contained electron dense filamentous structures. Similar structures were observed in the lipid vacuoles. Thus, a functional relationship between the cytoplasmic slashes and the lipid vacuoles is suggested. A unique structure was observed, termed dome-like cells, located between the epithelial cells and the basement membrane. These cells were characterized by the extensive presence of pleomorphic mitochondria and compact lamellae of granular endoplasmic reticulum (GER) in the form of finger prints. The gland was found to be actively secreting porphyrins as well as lipids. Cellular debris was also seen in the tubular lumina. Myoepithelial cells with their spindle shape and elongated nuclei were evident between the basement membrane and the secretory epithelium. Sparse interstitial tissue was observed in-between the gland tubules of both male and female gerbils. Macrophages, dendritic melanocytes and lymphocytes are the most represented cellular components of the interstitium. Further studies are required to investigate the function of the dome-like cells as well as the role of lymphocytes in the rodents Harderian gland.