The ultrastructure of signet-ring cell non-Hodgkin's lymphoma

A rare presentation of gastric signet ring cells: signet ring cell lymphoma

We herewith present a rare and interesting case of gastric signet ring cell lymphoma (SRCL) in a 40-year-old retroviral positive lady. SRCL is a rare morphological variant of nodal lymphomas.Biopsy from the suspected lesion in the stomach showed diffuse sheets of cells with a large central vacuole displacing the nucleus to the periphery of the cell, imparting signet ring cell morphology. Negative reaction to PAS (Periodic acid Schiff) stain and subsequent strong positivity for the immunohistochemical markers such as CD45 (Leucocyte commonantigen) and CD20, a B-cell marker helped us to arrive at a diagnosis of signet ring B- cell lymphoma.

Extreme Signet Ring Cell Change in a Large B-Cell Lymphoma of Follicular Origin

We report a large B-cell lymphoma of follicular origin with extreme signet ring cell differentiation. Initially classified as follicular lymphoma on a fine needle core biopsy, the presence of cohesive sheets of extrafollicular signet ring cells triggered an excisional biopsy for further characterization. The excised lymph node revealed focal follicular hyperplasia, follicular lymphoma, and a neoplasm composed of vague nodules and sheets of large atypical cells, all of which virtually exhibited large clear intracytoplasmic vacuoles with peripheral displacement of nuclei. The tumor cells were negative for mucin and lacked immunoreactivity with pancytokeratin, but were strongly immunoreactive with CD20, BCL-2, BCL-6, and CD10 antibodies. Electron microscopy studies revealed electron-lucent vacuoles with no particular internal structure. This case is unique in that extreme signet ring cell differentiation somewhat obscured the true cytological identity of the interfollicular lymphoma and suggested alternative diagnoses.

Ultrastructure of medullary thymic epithelial cells of autoimmune regulator (Aire)-deficient mice

The significance of the autoimmune regulator (Aire) transcription regulator in establishing central tolerance has recently been elucidated in great detail. Still, the role of Aire in medullary thymic epithelial cell (mTEC) physiology is not fully understood. To shed more light on this issue, we studied the ultrastructure of mTECs in Aire-deficient thymus. We show that all types of mTECs show ultrastructural signs of activation and increased intracellular traffic, which suggests that in the absence of Aire their physiology is impaired. Type 6 'large' mTECs are fully developed in Aire-deficient mice and more frequent than in the normal thymus. The frequency of type 5 'undifferentiated' mTECs is also increased. Collectively, our results suggest that the role of Aire in the physiology of mTECs could be more profound and not restricted only to the presentation of self-tissue-restricted antigens and/or apoptosis of end-stage fully mature cell types.

Cutaneous B-cell lymphoma with signet ring-cell morphology: a clinicopathologic and immunohistochemical study of three cases

Three cases of primary cutaneous B-cell lymphoma with prominent signet ring-cell features are presented. The patients were three men between the ages of 37 years and 74 years (average, 55.5 years). Clinically, the three patients presented with multiple skin nodules. In one patient, the nodules had been present for approximately 5 weeks, although in the two other patients, the nodules were of unknown duration. The lesions were located in the upper extremities (forearm) and measured from 2 cm to 3 cm in diameter. No evidence of lymphadenopathy was observed in any of the patients. Surgical excision of the nodules was performed. Histologically, in two cases, the superficial and deep dermis was replaced by a diffuse cellular proliferation, and in one patient, the tumor cell population adopted a nodular pattern of growth involving adnexal structures and infiltrating the subcutaneous fat. In all cases, the tumors were composed of cells showing signet ring-cell features, with striking indentation of the nuclei toward the periphery of the cell. Immunohistochemical studies using antibodies for B-cell and T-cell markers (L-26 and UCHL) as well as antibodies for leukocyte common antigen, keratin, and kappa and lambda light chains were performed in all cases. The tumor cells showed a positive reaction for leukocyte common antigen, L-26, and lambda light chain restriction. Follow-up information was only available in one patient, who has remained alive and well 2 years after diagnosis without evidence of progression of the disease. The present cases highlight the importance of recognizing this unusual morphologic type of lymphoma so as to arrive at a correct diagnosis.

Signet-ring cell variant of small lymphocytic lymphoma with a prominent sinusoidal pattern

Signet-ring cell lymphoma is a rare morphologic variant of non-Hodgkin's lymphoma characterized by neoplastic lymphoid cells with cytoplasmic vacuoles or eosinophilic globules that impart a signet-ring cell morphology. Although most cases are variants of follicular center B-cell lymphomas, this pattern also can be seen in T-cell lymphomas. An indolent clinical course and prolonged survival have characterized the majority of published cases. We document the case of a 62-year-old African-American woman with diffuse small lymphocytic signet-ring lymphoma having a predominant sinusoidal growth pattern, which, to our knowledge, has not been previously reported. The prominent sinusoidal pattern of signet-ring lymphocytes contributes to its confusion with metastatic signet-ring cell adenocarcinoma. The correct diagnosis is greatly facilitated by the use of appropriate immunohistochemical stains for lymphoid markers.

Pancreatic endocrine tumor with signet ring cell features: a case report with novel ultrastructural observations

The case of a malignant pancreatic endocrine neoplasm with an unusual signet ring cell appearance is reported. The tumor was resected from a 30-year-old man with a 4.0-cm tumor in the body of the pancreas diagnosed by computerized tomographic (CT) scan. The resected tumor had a unique morphology characterized by numerous mucin-negative, signet ring cells, which were argyrophilic and immunoreactive for cytokeratin (CAM 5.2), chromogranin, synaptophysin, neuron specific enolase, and gastrin. Dense-core neurosecretory-type granules and numerous cytoplasmic lamellar inclusions were identified by electron microscopy. These inclusion bodies consisted of multilayered concentric osmiophilic lamellae (myelin figures), which most likely represent an abnormal accumulation of degenerating organelles. Two years later, the patient developed an abdominal recurrence of the tumor, confirming its malignant behavior. This case expands the spectrum of pancreatic endocrine tumors to include an aggressive signet ring cell tumor with a novel ultrastructural basis.

Anaplastic large-cell lymphoma (Ki-1 lymphoma) and diffuse large-cell immunoblastic lymphoma: two diagnostic problem cases

Electron microscopy can be used to establish diagnoses in some otherwise difficult cases of neoplasia, but it is not generally regarded as important in the diagnosis of lymphoma. However, in some cases of anaplastic tumors not initially recognized as lymphomas, electron microscopy can prove quite valuable. Two cases are reported in which lymphoma was not suspected on the basis of the histologic findings, but was diagnosed by electron microscopy. Case 1 involved a 60-year-old woman who presented with a retroperitoneal mass that was located primarily in the body of the psoas muscle. Nuclear pockets were seen with electron microscopy. Ultimately she was diagnosed with anaplastic large-cell lymphoma (Ki-1 lymphoma). Case 2 involved a 43-year-old male with retroperitoneal lymphadenopathy, renal failure, polyclonal gammopathy, and a febrile illness. Signet-ring cells without junctions were identified with electron microscopy. Immunoperoxidase stains confirmed diffuse large-cell immunoblastic lymphoma.

Signet-ring sinus histiocytosis: a reactive disorder that mimics metastatic adenocarcinoma

BACKGROUND

Signet-ring sinus histiocytosis is a rare and distinctive reactive disorder recently observed in the axillary lymph nodes of patients with breast carcinoma. This form of sinus histiocytosis closely resembles and can easily be confused with metastatic adenocarcinoma.

METHODS

To determine the incidence of this reactive process in lymph nodes from different anatomic sites, broaden its morphologic spectrum, and discuss the differential diagnosis, the authors examined lymph nodes from 316 radical prostatectomy specimens, 184 modified radical mastectomy specimens, 108 colectomy specimens, 57 gastrectomy specimens, and 27 radical hysterectomy specimens. These surgical procedures were performed to treat carcinoma of the prostate, breast, colon, stomach, and uterine cervix, respectively. A total of 9741 lymph nodes were histologically examined. The lymph nodes containing sinus signet-ring cells were stained with mucicarmine, Alcian blue, and periodic acid-Schiff stains (PAS). Immunostains for epithelial, lymphoid, and histiocytic markers were also performed. In two cases, tissue was retrieved from the paraffin block and subsequently processed for electron microscopic examination.

RESULTS

Only 4 of 316 radical prostatectomy specimens (1.2%) and 2 of 184 axillary dissections (1.08%) contained lymph nodes with signet-ring sinus histiocytosis. Of 9741 lymph nodes reviewed, 37 (24 pelvic and 13 axillary lymph nodes) had signet-ring sinus histiocytosis, for an incidence of 0.38%. Microscopically, the signet-ring histiocytes lacked nuclear atypia and were mucin negative. In two cases, clusters of histiocytes with rounded, eosinophilic, diastase resistant, PAS positive cytoplasmic globules were observed. Both types of signet-ring cells showed reactivity for histiocytic markers and were negative for cytokeratin and lymphoid markers. By electron microscopy, most histiocytes were shown to have a large empty vacuole that displaced the nucleus. Granular material was observed in some of the vacuoles. Some histiocytes exhibited a rounded cytoplasmic body composed of central electron dense, granular material and a rim of microfibrils. No lipid droplets were identified.

CONCLUSIONS

Signet-ring sinus histiocytosis is a rare and distinctive reactive disorder found incidentally in the pelvic and axillary lymph nodes of patients with carcinoma of the prostate and breast, respectively. Although this histiocytic reaction mimics metastatic adenocarcinoma and signet-ring cell lymphoma, it can be identified by careful cytologic analysis together with positive reactivity for histiocytic markers, negative mucin stains, and lack of reactivity for epithelial and lymphoid markers. The etiology and pathogenesis of this unusual form of sinus histiocytosis remains unclear.

Malignant peripheral nerve sheath tumor with prominent intracytoplasmic vacuolation: report of a case

A case of malignant peripheral nerve sheath tumor with uncommon features is reported. A mass was noted in the left thigh of a 16 year old man. Histologically, most areas of the tumor exhibited the typical appearance of malignant peripheral nerve sheath tumor, but some tumor cells had rounded nuclei and cytoplasm, resembling an epithelioid pattern. It was noted that some rounded tumor cells showed prominent intracytoplasmic vacuolation. Immunohistochemically, almost all of the tumor cells, including the rounded and vacuolated ones, were positive for S-100 protein and vimentin. Electron microscopic study revealed well-developed cytoplasmic processes, intracytoplasmic intermediate-sized filaments, basement lamina formation and extracellular long-spacing collagens. These findings were compatible with those of Schwann cell differentiation. Moreover, ultrastructurally, the vacuolated spaces contained a few granular materials and were derived from the dilatation of the rough endoplasmic reticulum. It is speculated that intracytoplasmic vacuolation in malignant peripheral nerve sheath tumor would be caused by degeneration of the tumor cells.

Fibril formation in the rough endoplasmic reticulum of lymphoma cells. A case report with histopathologic, immunohistochemical, electron and immunoelectron microscopic studies

Signet ring cell lymphoma (SRCL) is a relatively new and infrequently described entity, characterized by an intracytoplasmic mass displacing the nucleus at the periphery. We present here a case of a Japanese female aged 73 with a retroperitoneal mass diagnosed as SRCL at autopsy. The neoplastic lymphoid cells showing signet ring appearance, due to the displacement of the nucleus to one side by intracytoplasmic eosinophilic inclusions, were immunoreactive for LCA, L26 and lambda light chains but PAS-negative. A small number of tumor cell nuclei demonstrated proliferating cell nuclear antigen-positive, but signet ring cells were negative. Ultrastructural study disclosed that fibrillary, lamellar or homogenous materials within rough endoplasmic reticulum of the tumor cells were selectively labeled by gold particles to anti-lambda antibody. A periodicity of 20-25 nm was observed in the fibrillary inclusions arranged haphazardly. The morphologic appearances of the case and the differential diagnosis are preceded by a review of the literature.

B-cell lymphoma with vimentin-positive cytoplasmic inclusions

A 60-year-old woman complaining of cervical lymphadenopathy was admitted to Keiyu General Hospital, Yokohama. Malignant lymphoma involving systemic lymph nodes and the bilateral tonsils was suspected by computed tomography. The biopsy diagnosis of the cervical lymph nodes was B-cell lymphoma, diffuse medium-sized cell type. The cleaved centrocytic lymphoma cells were immunoreactive for CD20 and CD22 but negative for immunoglobulins. Characteristically, a considerable number of neoplastic lymphocytes possessed eosinophilic round inclusions in the cytoplasm. The inclusions were green in color by Papanicolaou staining, whereas they appeared vacuole-like in Giemsa-stained preparations. Ultrastructural study confirmed the presence of aggregates of intermediate-sized filamentous structures mainly in the perinuclear area. The rough endoplasmic reticulum and Golgi apparatus were poorly developed. Immunocytochemical staining using cytologic specimens and fresh-frozen sections disclosed that the inclusions were composed of vimentin filaments. Morphologic similarities to signet ring cell lymphoma are discussed.