True histiocytic lymphoma: a morphologic, immunohistochemical, and molecular genetic study of 13 cases

Lymph node reticulum cell neoplasm with progression into cytokeratin-positive interstitial reticulum cell (CIRC) sarcoma: a case study

AIMS

To detail on sequential biopsies the morphological and immunohistochemical features of a case of primary lymph nodal fibroblastic reticulum cell (FBRC) tumour which progressed into a clinically aggressive cytokeratin-positive interstitial reticulum cell (CIRC) sarcoma.

METHODS AND RESULTS

A 70-year-old female underwent surgical excision of an enlarged submandibular lymph node. The nodal architecture was effaced by a neoplastic proliferation of medium to large cells, round to oval to spindle in shape, growing in a storiform pattern. The tumour stained for vimentin, CD68, factor XIIIa, alpha1-antitrypsin, fascin and actin. Dendritic and endothelial cell markers were negative. A diagnosis of FBRC tumour was made by combining pathological and clinical data. The patient received no therapy but 5 months later the tumour relapsed, exhibiting a deceptively pleomorphic cytology, phenotypic changes (strong cytokeratin positivity), intense p53 expression and aggressive clinical course with fatal outcome. In-situ hybridization for Epstein-Barr virus was negative.

CONCLUSIONS

We speculate that the morphological changes and p53 expression of the relapsing neoplasm might reflect tumour cell dedifferentiation, in keeping with the aggressive clinical course. The intense p53 expression suggests that this oncoprotein might also play a role in reticulum cell tumorigenesis.

Fine-needle aspiration cytology: True histiocytic lymphoma/histiocytic sarcoma

True histiocytic lymphoma/histiocytic sarcoma is an extremely rare, malignant histiocytic tumor. This report is of such a case in a 52-yr-old woman. Fine-needle aspiration (FNA) smears showed large pleomorphic nuclei, prominent nucleoli, moderately dense abundant cytoplasm, and scattered cells with cytoplasmic vacuoles and some with reniform nuclei. Small numbers of background lymphocytes and benign histiocytes were present as well as many multinucleated tumor cells. The immunophenotype was CD45, Lysozyme, CD68 (PGMI), CD43, and S-100 positive. Genotypic analysis revealed a germline configuration. This type of tumor has a large cytological differential diagnosis and immunophenotyping is essential for diagnosis.

Histiocytic lesions involving the bone marrow

Histiocytic lesions involving the bone marrow include a number of reactive and neoplastic disorders. This article discusses the morphologic, immunophenotypic, and genotypic features of a variety of diseases associated with histiocytes and/or monocytes. Lysosomal storage disorders and hemophagocytic syndromes are often first diagnosed by bone marrow examination. Granulomas involving the bone marrow may also be the first indication of a systemic disorder. Apart from acute and chronic monocytic leukemias, the bone marrow is rarely involved by malignant histiocytic disorders, of which Langerhans cell histiocytosis is the most common.

Cytologic and immunocytochemical findings of anaplastic large cell lymphoma: analysis of ten fine-needle aspiration specimens over a 9-year period

BACKGROUND

Anaplastic large cell lymphoma (ALCL) has raised much controversy in the field of hematolymphoid pathology. Its nature is becoming better characterized with recent advances in molecular genetics. However, to the authors' knowledge, a detailed description of the fine-needle aspiration (FNA) cytology of ALCL is lacking and the application of immunocytochemical study, including immunostaining for anaplastic lymphoma kinase (ALK) protein, to cytology samples has not been studied to date.

METHODS

The authors reviewed 10 FNA specimens of ALCL from 8 patients encountered at Pamela Youde Nethersole Eastern Hospital and Queen Mary Hospital in Hong Kong over a 9-year period from early 1993 to the end of 2001. The cytologic and immunocytochemical findings (including ALK protein overexpression) of the specimens were correlated with histologic and immunohistochemical findings of surgical biopsy specimens.

RESULTS

Six of the eight patients had ALCL of the common variant, whereas the remaining two patients had ALCL of the small cell variant. FNA specimens of ALCL of the common variant yielded many loosely dispersed "hallmark" cells that contained eccentric kidney-shaped or embryo-like nuclei, several prominent rod-shaped or angulated basophilic nucleoli, and abundant amphophilic cytoplasm. "Doughnut" cells, tumor cells with multilobated nuclei, and multinucleated giant cells with a wreath-like arrangement of nuclei occasionally were found. A small number of "plasmacytoid" tumor cells, nondescript small round tumor cells, and reactive polymorphs also was present. In contrast, "plasmacytoid" cells and nondescript small to medium-sized tumor cells represented the predominant cell population in ALCL of the small cell variant. The "plasmacytoid" appearance was exaggerated further in air-dried smears. In air-dried smears, small intracytoplasmic vacuoles and scanty azurophilic granules also were noted. On immunocytochemical study performed using the cell block materials, the majority of tumor cells demonstrated membranous and paranuclear "dot-like" positivity for CD30. The staining for epithelial membrane antigen, leukocyte common antigen, and T-cell markers was variable. Positive staining for ALK protein was demonstrated beautifully in two of the cases.

CONCLUSIONS

Despite the wide morphologic spectrum of ALCL, a definitive diagnosis on the basis of FNA cytology is possible on careful interpretation of the cytologic features and a high index of suspicion. The cytologic diagnosis can be confirmed further with proper application of immunostaining to cell block sections. Immunocytochemical study for ALK protein, which provides useful prognostic information, also can be demonstrated satisfactorily using cytology samples.

Histiocytic sarcoma involving the central nervous system: clinical, immunohistochemical, and molecular genetic studies of a case with review of the literature

Histiocytic sarcoma (HS) is a rare disease, and there has been much confusion concerning the diagnostic criteria for this entity. Since immunohistochemical and cytogenetic techniques have become more universally available, many cases initially diagnosed as histiocytic sarcoma have been reclassified as other diseases. We describe a case of HS that presented as a single mass lesion in left occipital lobe. At autopsy the tumor also involved the meninges as a thick exudate. Histologic examination showed numerous large pleomorphic malignant cells with areas of necrosis, numerous neutrophils, and phagocytosis by tumor cells. Immunohistochemically, the tumor cells stained positively with antibodies directed against most histiocytic markers and did not stain with antibodies directed against myeloid markers, dendritic markers, CD30, ALK1, or other lymphoid markers. Molecular cytogenetic analysis showed no rearrangement [i.e. t(2;5) translocation or other variant] by fluorescence in situ hybridization. The T-cell receptor-gamma chain by multiplex polymerase chain reaction showed a polyclonal pattern. No heavy or light chain gene rearrangements were found. To our knowledge, this is the first reported autopsy case of this rare entity primarily involving the brain and meninges.

Tumours of histiocytes and accessory dendritic cells: an immunohistochemical approach to classification from the International Lymphoma Study Group based on 61 cases

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.

Primary histiocytic lymphoma of the central nervous system: a neoplasm frequently overshadowed by a prominent inflammatory component

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.

Malignant histiocytosis in cattle

Malignant histiocytosis was diagnosed in 4 cows. In all cases the tumor tissues were composed of cytologically atypical histiocytes with evidence of erythrophagocytosis. The tumor in case 1 appeared highly anaplastic with marked nuclear pleomorphism, and had areas of spindle cell differentiation, but had no relation to malignant fibrous histiocytoma. The neoplastic tissue in case 2, characterized by cohesive growth of tumor cells, was distinguishable from anaplastic carcinoma cells by cytokeratin immunostaining. There were many hemosiderin-laden neoplastic cells suggestive of high phagocytic activity in a lymph node of case 3. The neoplastic cells in case 4, frequently multinucleated, were less atypical than in the other cases. All cases expressed histiocyte-associated markers (lysozyme and HAM56), and were negative for cytokeratin, S100, and T- and B-cell lineage-specific markers (CD3 and CD79a). The most frequent HAM56 immunoreactivity was detected in case 4, and the giant, multinucleated forms, reminiscent of epithelioid cell differentiation. seemed not to indicate cytological pleomorphism as a result of neoplastic transformation.

Pseudolymphomatous folliculitis: a clinicopathologic study of 15 cases of cutaneous pseudolymphoma with follicular invasion

We report the clinical, histopathologic, and immunohistologic features of 15 cases of pseudolymphomatous folliculitis (PLF). The patients comprised seven males and eight females (mean age, 38.6 years; age range, 2-67 years). All patients had dome-shaped or flat-elevated nodules suggestive of cutaneous lymphoid hyperplasias (CLHs). The lesions were solitary in all 15 cases, except in one case with duplex lesions. All lesions were located on the face and measured less than 1.5 cm. In 14 cases with one lesion each, five lesions showed rapid regression after incisional biopsy, whereas the remaining nine underwent excisional biopsy. In the case with duplex lesions, one regressed spontaneously after excisional biopsy of the other. Histopathologically, all PLFs showed dense lymphocytic infiltrates from the dermis to the subcutis simulating cutaneous lymphomas. The walls of hair follicles in all cases were enlarged and irregularly deformed with their epithelium blurred by lymphocytic infiltrates; we called this change "activation" of hair follicles. In nine cases, many atypical lymphocytes were intermingled; three of these cases had been misdiagnosed as cutaneous T-cell lymphoma at other institutions. Immunohistologically, 10 and 5 cases showed predominantly B cells and predominantly T cells, respectively. Remarkably, all lesions showed increased numbers of perifollicular histiocytes expressing anti-S-100 protein and CD1a, and seven lesions showed histiocytes in aggregates. We conclude that PLF is a subset of CLH with characteristic clinical and pathologic features showing perifollicular clustering of T-cell-associated dendritic cells with activation of pilosebaceous units. PLF is an entity to be differentiated from malignant lymphomas and other cutaneous pseudolymphomas.