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Query: UNIPROT:P06126 (CD1a)
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True histiocytic lymphoma, as defined by strict criteria, is a very rare neoplasm. We describe three cases occurring as primary tumors in the central nervous system. The patients, two females and one male, ranged in age from 11 to 69 years. The tumors involved the brain in two cases and spinal cord in one, with a size ranging from 7 to 17 mm. Two patients died at 4 months and 8 months, respectively, and one was alive with disease at 5 months. Pathologically, the tumors comprised groups and sheets of noncohesive large cells with pleomorphic vesicular nuclei, distinct nucleoli, and abundant eosinophilic cytoplasm. A dense inflammatory infiltrate consisting of neutrophils, lymphocytes, plasma cells, and histiocytes was present, with multiple foci of necrosis and abscess formation. All three cases demonstrated an identical immunophenotype: positive for CD68 and lysozyme; focally positive for S-100 protein, CD45RB, and CD4; and negative for CD3, CD20, CD21/CD35, CD1a, CD30, ALK1, myeloperoxidase, glial fibrillary acidic protein, and cytokeratin. The proliferative index ranged from 20% to 35%. Ultrastructural examination further confirmed the histiocytic nature of the tumor cells, characterized by irregularly folded or multisegmented nuclei and abundant cytoplasm containing lysosomes; Birbeck granules, interdigitating cell processes, and cell junctions were not found. Although the presence of abundant inflammatory cells could obscure the neoplastic histiocytes, making the distinction from inflammatory conditions difficult, awareness of this unusual histologic feature and the invariable finding of pleomorphic cells in some areas of the lesion permit the correct diagnosis to be made.
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PMID:Primary histiocytic lymphoma of the central nervous system: a neoplasm frequently overshadowed by a prominent inflammatory component. 1168 53

Neoplasms of histiocytes and dendritic cells are rare, and their phenotypic and biological definition is incomplete. Seeking to identify antigens detectable in paraffin-embedded sections that might allow a more complete, rational immunophenotypic classification of histiocytic/dendritic cell neoplasms, the International Lymphoma Study Group (ILSG) stained 61 tumours of suspected histiocytic/dendritic cell type with a panel of 15 antibodies including those reactive with histiocytes (CD68, lysozyme (LYS)), Langerhans cells (CD1a), follicular dendritic cells (FDC: CD21, CD35) and S100 protein. This analysis revealed that 57 cases (93%) fit into four major immunophenotypic groups (one histiocytic and three dendritic cell types) utilizing six markers: CD68, LYS, CD1a, S100, CD21, and CD35. The four (7%) unclassified cases were further classifiable into the above four groups using additional morphological and ultrastructural features. The four groups then included: (i) histiocytic sarcoma (n=18) with the following phenotype: CD68 (100%), LYS (94%), CD1a (0%), S100 (33%), CD21/35 (0%). The median age was 46 years. Presentation was predominantly extranodal (72%) with high mortality (58% dead of disease (DOD)). Three had systemic involvement consistent with 'malignant histiocytosis'; (ii) Langerhans cell tumour (LCT) (n=26) which expressed: CD68 (96%), LYS (42%), CD1a (100%), S100 (100%), CD21/35 (0%). There were two morphological variants: cytologically typical (n=17) designated LCT; and cytologically malignant (n=9) designated Langerhans cell sarcoma (LCS). The LCS were often not easily recognized morphologically as LC-derived, but were diagnosed based on CD1a staining. LCT and LCS differed in median age (33 versus 41 years), male:female ratio (3.7:1 versus 1:2), and death rate (31% versus 50% DOD). Four LCT patients had systemic involvement typical of Letterer-Siwe disease; (iii) follicular dendritic cell tumour/sarcoma (FDCT) (n=13) which expressed: CD68 (54%), LYS (8%), CD1a (0%), S100 (16%), FDC markers CD21/35 (100%), EMA (40%). These patients were adults (median age 65 years) with predominantly localized nodal disease (75%) and low mortality (9% DOD); (iv) interdigitating dendritic cell tumour/sarcoma (IDCT) (n=4) which expressed: CD68 (50%), LYS (25%), CD1a (0%), S100 (100%), CD21/35 (0%). The patients were adults (median 71 years) with localized nodal disease (75%) without mortality (0% DOD). In conclusion, definitive immunophenotypic classification of histiocytic and accessory cell neoplasms into four categories was possible in 93% of the cases using six antigens detected in paraffin-embedded sections. Exceptional cases (7%) were resolvable when added morphological and ultrastructural features were considered. We propose a classification combining immunophenotype and morphology with five categories, including Langerhans cell sarcoma. This simplified scheme is practical for everyday diagnostic use and should provide a framework for additional investigation of these unusual neoplasms.
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PMID:Tumours of histiocytes and accessory dendritic cells: an immunohistochemical approach to classification from the International Lymphoma Study Group based on 61 cases. 1212 Dec 33

Conjunctival lymphoid follicles (CLFs), present in normal individuals, undergo hyperplasia upon conjunctival infection by a specific array of pathogens; infection-associated enlargement of draining preauricular lymph nodes suggests that conjunctival follicles participate in the afferent limb of acquired immune responses for the ocular surface. The present study was performed to delineate the structural and lymphoid anatomy of CLFs in the baboon (Papio anubis), a non-human primate conjunctival model with close similarity to the human. Conjunctiva from both eyes, along with mesenteric lymph node, spleen, tonsil, and ileum controls were harvested from ten baboons at necropsy, and studied by histochemical and immunohistochemical methods. Baboon conjunctival follicles were identified as dense oval collections of leukocytes in the substantia propria with infiltration into a thinned overlying conjunctival epithelium. Goblet cells were universally absent, the overlying mucin layer was attenuated, and the follicle-associated epithelium (FAE) demonstrated comparatively diminished alkaline phosphatase expression. The basement membrane overlying each follicle appeared discontinuous. CD4-positive T lymphocytes were distributed in parafollicular areas and to a lesser degree in follicle germinal centers. B lymphocytes formed the predominant cell in follicles, and also heavily infiltrated the FAE. B cell IgM expression was prominent in germinal centers, while IgD staining occurred in a horseshoe-shaped distribution in the follicle mantle zone. Although B cell IgA expression was noted in the non-follicular conjunctiva, IgA expression was inconspicuous within conjunctival follicles. S-100- and CD1a-positive dendritic cells were found in FAE, while fascin-positive mature dendritic cells appeared in the deeper areas of each follicle. CD68-positive macrophages were dispersed throughout the follicles. CD35-positive follicular dendritic cells were observed only in germinal centers. CLFs appear highly organized consistent with a role in the adaptive immune response to conjunctival pathogens.
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PMID:Structural and cellular architecture of conjunctival lymphoid follicles in the baboon (Papio anubis). 1274 51

Sarcomas derived from immune accessory cells are uncommon malignancies, most of them occurring in lymph nodes while extra nodal sites are very rarely affected. Based on the immune profile, the cells that give origin to these neoplasms are currently divided in: follicular dendritic cell (FDC), interdigitating dendritic cell (IDC), indeterminate cell and Langerhans cell. A case of a dendritic cell sarcoma arising in the alveolar ridge mucosa in a 50-year-old female is reported here. The lesion presented as a nodular mass without defined borders and covered by reddish mucosa. Histologically, the tumour was composed of spindle-shaped cells with large nuclei and abundant cytoplasm, arranged in variable patterns as storiform and whorled and revealing interspersed lymphocytes. No capsule could be seen and the neoplasm extended up to the lining epithelium. Immunohistochemically, the spindle cells were positive for vimentin, S-100 protein, CD1a, factor XIIIa and focally to smooth-muscle actin, but were negative for CD21, CD35, CD23 and caldesmon--all markers of follicular dendritic cells. In conclusion, the present case has morphologic pattern of dendritic cell sarcoma and the immunophenotype is compatible with IDC cells or with intermediate dendritic cells and demonstrates the overlap of features among these entities.
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PMID:Dendritic cell sarcoma of the oral cavity. 1474 67

While tumors of dendritic cell lineage may have overlapping histomorphologic features, most but not all cases can be classified using an immunohistochemical panel, including CD21, CD23, CD35, CD1a, and S-100. Based on observations that clusterin is expressed in benign follicular dendritic cells, clusterin expression in 32 dendritic cell tumors was evaluated. Diffuse strong staining for clusterin was seen in 12 of 12 follicular dendritic cell tumors. Two of these cases were negative for traditional markers (CD21, CD23, CD35); they were classified based on characteristic ultrastructural features. Three of 6 interdigitating dendritic cell tumors were negative for clusterin and 3 showed focal weak positivity. Clusterin staining in Langerhans cell histiocytosis ranged from negative (6 of 14) to weak/moderate (8 of 14). Follicular dendritic cell tumors behaved as benign tumors or low-grade sarcomas. Interdigitating dendritic cell tumors demonstrated a widely variable behavior, ranging from benign to rapidly fatal disease. Based on this initial study, strong clusterin staining supports a diagnosis of follicular dendritic cell tumor. Thus, staining for clusterin is useful in classification of dendritic cell tumors, particularly when the more common markers of follicular dendritic cells are not expressed.
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PMID:Clusterin expression distinguishes follicular dendritic cell tumors from other dendritic cell neoplasms: report of a novel follicular dendritic cell marker and clinicopathologic data on 12 additional follicular dendritic cell tumors and 6 additional interdigitating dendritic cell tumors. 1525 4

Histiocytic sarcoma is a rare malignant neoplasm that occurs in lymph nodes, skin, and the gastrointestinal tract. Many previously published cases were likely misdiagnosed examples of non-Hodgkin lymphoma. Only small numbers of bona fide examples exist in the world literature; cases arising primarily at extranodal sites are not well described and often seem to go unrecognized. To characterize these tumors further, 14 extranodal histiocytic sarcomas were analyzed. Hematoxylin and eosin sections were reexamined, immunohistochemistry was performed, and clinical details were obtained from referring hospitals. Eight patients were female and 6 male (median age, 55 years; range, 15-89 years). All patients presented with a solitary mass, ranging in size from 1.8 to 12 cm (median 6.8 cm). Seven tumors arose in soft tissue (6 lower limb; 1 upper limb), 5 in the gastrointestinal tract (1 involving both stomach and colon, 1 ileum, 2 rectum, 1 anus), 1 in the nasal cavity, and 1 in the lung. Three gastrointestinal tract tumors also involved regional lymph nodes, and 1 involved the liver. Most cases had infiltrative margins. The tumors were generally composed of sheets of large epithelioid cells with abundant eosinophilic cytoplasm, oval to irregular nuclei, vesicular chromatin, and large nucleoli. Binucleated cells were common, and 6 cases contained tumor giant cells. Mitoses ranged from 1 to 64 per 10 HPF (median 11 per 10 HPF). Necrosis was present in 8 cases. Nearly all tumors showed a striking inflammatory infiltrate, most often of neutrophils or lymphocytes. All cases were reactive for LCA, CD45RO, and CD68 (KP1 and PG-M1); 13 of 14 (93%) expressed CD4, 12 of 14 (86%) lysozyme, 8 of 10 (80%) CD31, 7 of 14 (50%) S-100 protein, and 5 of 14 (36%) focal CD1a. Two tumors showed weak, focal cytoplasmic positivity for CD30, and 1 for epithelial membrane antigen. The tumors were negative for ALK-1, CD21, CD35, CD3, CD20, CD34, myeloperoxidase, HMB-45, and keratins. Gastrointestinal tract cases were negative for c-kit and desmin. Six patients were treated with postoperative radiation and 7 with chemotherapy (CHOP or ProMACE-MOPP). Follow-up was available for 10 patients (median, 24 months; range, 4 months to 11 years). Two tumors recurred locally, and 5 patients developed distant spread: 3 to lymph nodes, 1 to lung, and 1 to bone. At the last follow-up, 2 patients have died of disseminated disease, 4 and 5 months following initial diagnosis. The patients who died thus far had the largest primary tumors. Histiocytic sarcoma may arise primarily in soft tissue and shows reproducible histologic features, including abundant eosinophilic cytoplasm and a prominent inflammatory infiltrate. Metastatic carcinoma, metastatic melanoma, and large cell non-Hodgkin lymphomas should be excluded by immunohistochemistry. Histiocytic sarcoma has the potential for an aggressive clinical course, most often with lymph node involvement. However, a subset of cases presenting with clinically localized disease have a favorable long-term outcome. Tumor size may be a prognostic factor.
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PMID:Extranodal histiocytic sarcoma: clinicopathologic analysis of 14 cases of a rare epithelioid malignancy. 1531 12

Tumors of dendritic reticulum cells are rare neoplasms that exhibit significant morphologic overlap with other malignancies. Fine-needle aspiration cytologic appearances of this neoplasm are not well understood. A 33-yr-old woman presented with a rapidly growing nodular mass in the right upper cervical region and right-sided ptosis. Fine-needle aspiration cytology of the mass showed dissociated as well as clustered, large, polygonal cells that showed high nuclear-cytoplasmic ratio. Nuclei were round, oval, or irregular in shape. Large and small blastoid forms with prominent nucleoli and chromatin clumping as well as binucleated cells and cells with lobulated nuclei were seen. Numerous mitoses were observed. The tumor cells expressed focal immunocytochemical reactivity to CD45 and CD68, but were negative for CD2, CD3, CD4, CD8, CD20, CD30, CD45RO, epithelial membrane antigen (EMA), cytokeratin, and HMB45. Histologic sections of the biopsy from the growth showed nodal tissue effaced by a tumor composed of large, pleomorphic neoplastic cells with some binucleate and multinucleate forms resembling Reed-Sternberg cells. The intervening stroma contained numerous small lymphocytes. Tumor cells expressed vimentin, S-100 protein, CD68, and MAC387, but were negative for LCA, CD1a, CD3, CD15, CD20, CD21, CD23, CD30, CD35, carcino-embryonic antigen, HMB45, cytokeratin AE1/3, EMA, myeloperoxidase, lysozyme, smooth-muscle actin, and desmin. The combined histologic and immunohistologic features suggested a histiocytic/dendritic reticulum cell neoplasm and a diagnosis of interdigitating dendritic reticulum cell sarcoma was made.
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PMID:Interdigitating dendritic reticulum cell sarcoma: cytologic, histologic and immunocytochemical features. 1594 93

A 70-year-old Japanese man presented to our hospital with a 1-month history of progressive general fatigue and anorexia. A physical examination revealed severe anemic condition, mild persistent splenomegaly, and no palpable surface lymph nodes. He had pleural effusion and ascites, though no malignant cells were detected in the effusion. He eventually died without any diagnosis of his disease. Immunohistochemical staining of his tumor after autopsy showed atypical cells that were negative for epithelial membrane antigen (EMA), keratin (AE1/3), keratin-20, vimentin, factor VIII, leukocyte common antigen (LCA/T200; CD45), myeloperoxidase (MPO), terminal deoxynucleotidyl transferase (TdT), lysozyme, CD1a, CD3, CD4, CD10, CD15, CD20 (L26), CD21, CD23, CD34, CD43, CD56, CD68, CD79a, CD138, and EBER-1 in situ. Only a few scattered cells expressed CD30, but they showed no staining for anaplastic large-cell lymphoma kinase (ALK). A few scattered cells expressed S-100 antigen and the majority of cells dominantly expressed dendritic cell-associated antigens (CD35, FDC, Ki-M1p). In conclusion, we found this unknown primary tumor to be consistent with a follicular dendritic cell tumor with anaplastic features.
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PMID:Follicular dendritic cell tumor as an unknown primary tumor. 1738 Apr 43

A panel of 380 commercially available monoclonal antibodies (mAbs) against human CD molecules from various sources was tested during the 8th Human Leukocyte Differentiation Antigen Workshop (HLDA8) for cross-reactivity on canine peripheral blood leukocytes by flow cytometry. In addition, all mAbs were used to label a 50:50 mixture of platelets and erythrocytes of the same dogs. This testing resulted in 51 cross-reacting mAbs. mAbs with specificity for CD9, CD29, CD42a, CD61, and CD41/CD61 showed cross-reactivity with canine platelets in a non-polymorphic and one mAb with the erythrocyte antigen CD235a in a polymorphic reaction pattern. Canine leukocyte-reactive mAbs included those with specificity for CD11a, CD11b, CD14, CD18, CD21, CD22, CD47, CD49d, CD49e, CD56, CD62L, CD91, CD94, and CD172a. In addition, several mAbs resulted in a staining pattern of canine cells which suggest that the canine epitope equivalents have an alternate expression pattern from that expected for humans (CD1a, CD35, CD44, CD45, CD75s, CD81). In summary, this study confirmed the reactivity of previously described cross-reactive mAbs with canine cells and resulted in the characterization of mAbs recognizing so far undetectable canine CD molecules.
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PMID:Reactivity of cross-reacting monoclonal antibodies with canine leukocytes, platelets and erythrocytes. 1764 96

Follicular dendritic cell (FDC) sarcoma, especially of extranodal origin, is an extremely rare malignancy of FDC origin, with only 1 case previously documented in the thyroid. The authors report the case of a 58-year-old female who presented with a painless mass in her neck. The neoplastic cells expressed monocyte/macrophage-specific marker CD68 (KP-1) and lysozymes and the dendritic cell-associated antigens CD35 and Fascin but was negative for CD1a, CD21, and CD23, most consistent with a diagnosis of FDC sarcoma. BIOMED-2 multiplex polymerase chain reaction analysis showed B-cell clonality in both tumor and its adjacent coexisting Hashimoto's thyroiditis. To the authors' knowledge, this is the first report of a rare entity of FDC sarcoma primarily involving the thyroid gland coexisting with Hashimoto's thyroiditis.
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PMID:Primary follicular dendritic cell sarcoma of the thyroid gland coexisting with Hashimoto's thyroiditis. 1944 67


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