Immunohistochemical classification of cutaneous pseudolymphomas: delineation of distinct patterns

Cutaneous Pseudolymphomas

The term cutaneous pseudolymphoma refers to benign reactive lymphoid proliferations in the skin that simulate cutaneous lymphomas. It is a purely descriptive term that encompasses various reactive conditions with a varied etiology, pathogenesis, clinical presentation, histology, and behavior. We present a review of the different types of cutaneous pseudolymphoma. To reach a correct diagnosis, it is necessary to contrast clinical, histologic, immunophenotypic, and molecular findings. Even with these data, in some cases only the clinical course will confirm the diagnosis, making follow-up essential.

Controversies and Considerations in the Diagnosis of Primary Cutaneous CD4+ Small/Medium T-Cell Lymphoma

Context.—Primary cutaneous CD4+ small/medium T-cell lymphoma is a provisional and controversial entity with a broad differential diagnosis. Despite being an uncommon lymphoma, it is a frequent diagnostic consideration in cutaneous biopsies with a dense lymphoid infiltrate because it shows overlapping features with reactive lymphoid hyperplasia (pseudolymphoma) and a variety of other primary cutaneous and systemic lymphomas. However, proper classification of this process is important for determining patient prognosis and treatment options.

Objective.—To review the clinical, morphologic, immunophenotypic, and genetic features of primary cutaneous CD4+ small/medium T-cell lymphoma and contrast those features with entities in the differential diagnosis.

Data Sources.—Applicable literature will be reviewed with emphasis on current controversies and distinguishing characteristics.

Conclusions.—Although many consider primary cutaneous CD4+ small/medium T-cell lymphoma to be indistinguishable from reactive lymphoid hyperplasia/pseudolymphoma, it can be differentiated from other primary cutaneous and systemic lymphomas. Patients with solitary lesions of primary cutaneous CD4+ small/medium T-cell lymphoma generally have an excellent prognosis. Nevertheless, a subset of patients who have been reported to meet criteria for this lymphoma have followed a more-aggressive course; however, those patients show some differing clinical, morphologic, and immunophenotypic features.

Cutaneous T-cell lymphoproliferative disorders: approach for the surgical pathologist: recent advances and clarification of confused issues

Cutaneous T-cell lymphoproliferative disorders (CTCLs) remain a subject of confusion and controversy. In this review, the authors discuss diagnostic criteria and classification, including the role of immunohistochemistry and gene rearrangement studies. In addition, cutaneous T-cell pseudolymphomas, the current status of parapsoriasis and other premalignant syndromes, and the clinicopathological variants of mycosis fungoides are discussed. CD30-positive lymphoproliferative disorders and a number of rare variants of CTCL including granulamatous slack skin, subcutaneous (panniculitic) T-cell lymphoma, gamma-delta cutaneous lymphoma, NK/NK-like T-cell lymphoma, and primary cutaneous CD8-positive epidermotropic cytotoxic T-cell lymphoma are also considered.

Reduced number of CD1a+ cells in cutaneous B-cell lymphoma

Cutaneous B-cell lymphoma is difficult to distinguish from pseudolymphoma. The histologic pattern and monoclonal restriction (immunohistochemical analysis and molecular biology) are the criteria used for differentiating these entities. CD1a+ dendritic cells have been observed in the infiltrates of T-cell lymphoma, but the presence of these CD1a+ cells has not been compared in B-cell lymphoma and pseudolymphoma. We studied the presence of CD1a+ cells on frozen sections of 23 B-cell lymphomas, 13 pseudolymphomas, and 17 T-cell lymphomas by immunohistochemical analysis. We found abundant CD1a+ dendritic cells in only 1 (4%) of 23 B-cell lymphomas, whereas in 8 (62%) of 13 pseudolymphomas and 17 (100%) of 17 T-cell lymphomas, strong CD1a staining was present. Our study demonstrates a distinct pattern of CD1a staining in the infiltrates of B-cell lymphoma and pseudolymphoma that may be of value in the differential diagnosis of these skin disorders.

Cutaneous pseudolymphoma, lymphomatoid contact dermatitis type, as an unusual cause of symmetrical upper eyelid nodules

We describe a 74-year-old woman who rapidly developed bilateral voluminous nodules on the upper eyelids, following 4 months' treatment for chalazion. Histological and immunohistochemical findings were suggestive of cutaneous pseudolymphoma (CPL), and extensive screening for malignant lymphoma (ML) remained negative. Cutaneous pseudolymphomas are inflammatory diseases that can simulate ML either clinically, histopathologically, or both. They are a rare cause of nodules of the upper eyelids, usually characterized by a benign evolution, that can be secondary to ultraviolet sensitivity, adverse reactions to systemic medications and contact sensitization, among others. In our case, epicutaneous patch tests were strongly positive for a series of allergens contained in the ophthalmological preparations used; therefore, they were suggestive that the patient had CPL, lymphomatoid contact dermatitis type. In addition, the patient had been treated previously with several drugs, known to cause CPL and immune dysregulation. Complete regression of the lesions required treatment with systemic steroids and chlorambucil. No relapse occurred within a 5-year follow-up period.

Cutaneous lymphoid hyperplasias

Benign hyperplastic lymphoid infiltrates of the skin (pseudolymphoma, older term) simulate lymphoma clinically and histologically. They can be divided into B-cell predominant (typical cutaneous lymphoid hyperplasia (CLH), angiolymphoid hyperplasia, Kimura's disease, and Castleman's disease) and T-cell predominant (T-cell CLH, lymphomatoid contact dermatitis, and lymphomatoid drug eruption). Both types may represent exaggerated reactions to diverse external antigens (insect bite, tattoo, zoster, trauma, among others). A composite assessment of clinical presentation and behavior, routine histology, immunophenotyping, and molecular studies is essential for the diagnosis of benign cutaneous lymphoid infiltrates. Treatment includes antibiotics, intralesional and systemic corticosteroids, excision, radiotherapy, and immunosuppressants. Treatment depends on the assessment and biologic behavior, which is usually benign. Molecular biologic analysis has shown that a significant proportion of cases harbor occult B- or T-cell clones (clonal CLH). Progression to overt cutaneous lymphoma has been observed in a minority of cases. Patients with clonal populations of B or T cells and persistent lesions should be closely observed for emergence of a lymphoma.

Angiogenesis in cutaneous lymphoproliferative disorders: microvessel density discriminates between cutaneous B-cell lymphomas and B-cell pseudolymphomas

The role of angiogenesis in neoplastic disorders is supported by the evidence that tumor growth beyond a certain size requires induction of new blood vessels. The extent of tumor-associated angiogenesis, measured as microvessel density (MVD), has shown to correlate with aggressiveness and the prognostic outcome in several malignant neoplasms. Few data have been reported on the angiogenic response in lymphoproliferative diseases. In this study, the MVD has been assessed in benign and malignant primary cutaneous B-cell lymphoproliferative disorders. MVD was determined in formaldehyde-fixed, paraffin-embedded specimens of primary cutaneous B-cell lymphomas (CBCL; n = 18) and cutaneous B-cell pseudolymphomas (B-PSL; n = 22) according to previously described protocols but was performed using computer-aided microscopic morphometry. The endothelial cells of microvessels were identified by immunohistochemical staining for factor VIII-related antigen and CD31. The MVD was 99 dots/mm2 for CBCL and 68 dots/mm2 for PSL, and a MVD of 115 dots/mm2 for CBCL and 73 dots/mm2 for PSL by using an antibody against factor VIII-related antigen and CD31 antigen, respectively. Univariate analysis revealed statistically highly significant differences in MVD between CBCL and B-PSL (P = 0.0036 with staining for factor VIII-related antigen and P = 0.0002 with staining for CD31 antigen). This study analyzes for the first time the angiogenic response in CBCL compared with that of B-PSL and demonstrates that MVD discriminates between CBCL and B-PSL. However, because of an overlap in the ranges of MVD in CBCL and PSL, the MVD is not useful as a diagnostic tool in individual cases.

Follicular B-cell pseudolymphoma

A 60-year-old woman presented with a 3-week history of a pruritic papulo-nodular eruption on the face and trunk after a bee sting. Histological examination showed a predominantly lymphocytic infiltrate with follicular centres and tingible body macrophages. Immunohistochemically, positive staining for both kappa and lambda light chains was noted. The eruption settled with oral antihistamine and topical corticosteroid. These findings support the diagnosis of follicular B-cell pseudolymphoma.

Mainly unmutated V(H) genes rearranged in B cells forming germinal centers in a cutaneous pleomorphic T-cell lymphoma

B cells in skin lesions of a pleomorphic cutaneous T-cell lymphoma with reactive germinal center hyperplasia were analyzed for their immunoglobulin V(H)DJ(H) gene rearrangements by micromanipulation and single cell polymerase chain reaction (PCR) analysis. In B lymphocytes located in germinal center-like structures, we found in 11/16 different V(H)DJ(H) rearrangements completely unmutated VH genes, suggesting that those cells did not undergo antigen-driven selection. Two V(H) genes showed more than 98% germ-line identity. In only three cells V(H) segments were somatically mutated to a higher extent, but two of these rearrangements were non-productive. These results differ markedly from what we have previously detected in B cells present in mycosis fungoides, another entity of cutaneous T-cell lymphomas where the Ig gene repertoire resembles the situation in peripheral blood with a significantly higher proportion of mutated V(H) genes. When investigating the large atypical B cells strongly expressing CD30 which were detected within the T-cell zone outside the germinal centers, we found again, in most cases, that the rearranged VH genes were completely unmutated. The B cells were of polyclonal origin. Due to this comparable Ig gene repertoire and mutational pattern, we suggest that these cells descend from the germinal center centroblasts which migrated into the T-cell zone and obviously became stimulated to express the CD30 marker. The micromanipulation technique and molecular analysis on the single cell level may provide an important input into our understanding of the mechanisms of immune regulation in cutaneous lymphomas.

Borrelial lymphocytoma--a historical case

We here describe a patient with a tick bite in the areola mammae in 1953 followed by erythema migrans. Twenty years later, after another tick bite in the axillary skin, also followed by erythema migrans, a large lymphatic infiltrate developed in the mammary skin, when the margin of the erythema reached the areola. The infiltrate resolved within a year without any therapy. Borrelial DNA was detected by polymerase chain reaction in the paraffin blocks of the lymphatic skin infiltrate. The patient died 9 years later of generalized lymphoma. A similar monoclonal immunoglobulin heavy chain gene rearrangement was detected both in the mammary skin lesion and in the lymphoma specimen.

Cutaneous pseudolymphoma in association with molluscum contagiosum

Cutaneous pseudolymphomas have been defined as benign lymphocytic infiltrates of the skin that simulate cutaneous lymphoma clinically or histologically. The authors report on a 2-year-old boy with a lesion of molluscum contagiosum in which the inflammatory infiltrate that surrounded a cystlike structure containing molluscum bodies consisted of atypical hyperchromatic mononuclear cells with abundant mitotic figures, some of them atypical. Immunohistochemical investigation demonstrated that the infiltrate was predominantly composed of T lymphocytes. A previous report documented pseudoleukemia cutis associated with molluscum contagiosum, and this report expands the spectrum of histopathologic pseudomalignancies that may be seen in lesions of molluscum contagiosum.

Cutaneous pseudolymphomas

Cutaneous pseudolymphoma refers to a heterogeneous group of benign reactive T- or B-cell lymphoproliferative processes of diverse causes that simulate cutaneous lymphomas clinically and/or histologically. The inflammatory infiltrate is bandlike, nodular, or diffuse and is composed predominantly of lymphocytes with or without other inflammatory cells. Depending on the predominant cell type in the infiltrate, cutaneous pseudolymphomas are divided into T- and B-cell pseudolymphomas. Cutaneous T-cell pseudolymphomas include idiopathic cutaneous T-cell pseudolymphoma, lymphomatoid drug reactions, lymphomatoid contact dermatitis, persistent nodular arthropod-bite reactions, nodular scabies, actinic reticuloid, and lymphomatoid papulosis. Cutaneous B-cell pseudolymphomas include idiopathic lymphocytoma cutis, borrelial lymphocytoma cutis, tattoo-induced lymphocytoma cutis, post-zoster scar lymphocytoma cutis, and some persistent nodular arthropod-bite reactions. This review attempts to discuss current aspects of the classification, pathogenesis, clinical spectrum, histopathologic and immunohistochemical diagnosis, and laboratory investigations for clonality in the various types of cutaneous pseudolymphomas.

Drug-induced immune dysregulation as a cause of atypical cutaneous lymphoid infiltrates: a hypothesis

The authors encountered 22 patients in whom a skin biopsy showed atypical lymphoid hyperplasia and in whom a subsequent drug history showed indigestion of one or more agents before lesional onset. In 13 patients, the biopsy had been performed to rule out a diagnosis of malignant lymphoma, whereas the other nine the clinical impression was that of a drug eruption. Among the more frequently prescribed agents were calcium-channel blockers, angiotensin-converting enzyme (ACE) inhibitors, antidepressants, antihistamines, beta-blockers, benzodiazepines and lipid-lowering agents, all of which are either known to perturb lymphocyte function or have been implicated as a cause of pseudolymphomata. Twelve of the patients were on two or more of these drugs. The effect of drug modulation on the clinical course was assessed. The clinical presentations were as one or more erythematous plaques or multiple infiltrative papules, or as solitary nodules. The patient had been on one or more of the aforementioned drugs from 2 weeks to 5 years before developing the lesions. Resolution of the eruptions occurred in 17 patients within 1 to 32 weeks (mean, 7 weeks) of discontinuing the medication. Five additional patients had complete excision of solitary lesions without recurrence. A history of atopy, autoimmune disease, or previous carcinoma was elicited in five patients. All biopsy specimens showed atypical lymphoid infiltrates, which assumed one or more of the following patterns: mycosis fungoides (MF)-like, a lymphomatoid vascular reaction, lymphocytoma cutis and follicular mucinosis. Based on the histopathology of the biopsied lesions and the clinical course being one of lesional resolution after cessation of drug therapy or excision of a solitary lesion without subsequent recurrence, a diagnosis of drug-associated lymphomatoid hypersensitivity was established in all specimens. A diagnosis of drug-associated pseudolymphoma should be excluded before a diagnosis of cutaneous lymphoma is rendered, and should be considered if the patient is on a drug known to alter lymphocyte function, particularly in the setting of systemic immune dysregulation or multidrug therapy where agent may act synergistically or cumulatively to alter lymphoid function. The authors postulate that the drug may promote an aberrant immune response to an antigen that may be the drug itself or some other stimulus. A skin biopsy may be particularly helpful, as the lesions of drug-associated pseudolymphoma have a morphology distinctive from malignant lymphoma.

Paraffin section immunohistochemistry as an adjunct to morphologic analysis in the diagnosis of cutaneous lymphoid infiltrates

In the skin, separation of selected lymphomas from lymphoid hyperplasia can be challenging. The authors examined 45 cutaneous lymphomas, excluding mycosis fungoides (26 small lymphocytic or mixed tumors; 19 large cell lymphomas), 10 "atypical" lesions, and 40 lesions of presumed lymphoid hyperplasia, comparing morphologic attributes of such proliferations with their immunophenotypes in paraffin sections. The object of this study was to determine whether immunologic data obtained from routinely-processed specimens could be used to further objectify morphologic interpretations. Features favoring lymphoma included a lesional epicenter in the lower dermis or subcutis; poor circumscription of lymphoid aggregates; and dissection of lymphoid cells between collagen bundles. Immunostains included antibodies to CD20, CD43, CD45, CD45RO, CD45RA, CD68, proliferating cell nuclear antigen (PCNA), and MB2. Eleven of 26 small lymphocytic or mixed-cell lymphomas and 3 of 10 "atypical" cases demonstrated an abnormal immunophenotype, including co-expression of CD43 and CD20 or non-physiological CD45RA distribution. In contrast, none of 40 cases with benign features manifested aberrant antigen expression. Thirty-one of 37 cases in which > or = 75% of the cells typed as B lymphocytes showed malignant morphologic features, 5 were "atypical" and possibly lymphomatous, and only one had benign features. PCNA stains showed greater positivity of the lymphoid nuclei in lymphomas, and a labeling index of > 30% was correlated with malignancy in this context. These observations indicate that immunostaining may provide useful adjunctive information in distinguishing benign from malignant cutaneous lymphoid proliferations in paraffin sections.

Classification of primary cutaneous T-cell lymphomas

The term cutaneous T-cell lymphoma designates a group of neoplasms of skin homing T-cells that show considerable variation in clinical presentation, histological appearances, immunophenotype and prognosis. The disadvantages of currently available histological classification schemes are discussed and a new classification is presented. This is based on a combination of clinical, histological and immunophenotypic criteria and it recognizes distinct clinico-pathological entities within this group of diseases.

Cutaneous B-cell lymphoma--a clinical, pathological and immunohistochemical study

Eleven cases of cutaneous B-cell lymphoma (CBCL) were studied. The ages at presentation ranged from 34 to 79 years (mean = 59.9 years). Six patients were female and five male. Five of the 11 patients had a solitary tumour and the other six had multiple tumours at initial presentation. According to Burg's classification, six cases were at stage I, two stage II, two stage III and one was at stage IV at initial presentation. Abnormalities in laboratory data were rare, except for serum lactic dehydrogenase values. Epidermotropism was not detected, and the area mainly affected by neoplastic cells was the reticular dermis (seven cases) and subcutis (four cases). Biopsy specimens from the patients analysed by immunohistochemical techniques on paraffin or cryostat sections showed CD20 and/or CD22 positivity. Biopsy specimens from two patients which showed CD10 positivity were diffuse large cell types by the working formulation and presented as pre-B-cell lymphoma. At least two groups of CBCL were demonstrable on the basis of prognosis. One was a benign low-grade lymphoma presenting with solitary tumours, mature B-cell markers and intermediate-grade pathology, and the other was a high-grade lymphoma with multiple tumours, pre-B-cell or mature B-cell markers and a poor prognosis.

Immunohistochemical detection of CD1A antigen in formalin-fixed and paraffin-embedded tissue sections with monoclonal antibody 010

The immunoreactivity of a CD1a monoclonal antibody (MAb), denoted 010, was investigated by means of the streptavidin-biotin-peroxidase method in formalin-fixed and paraffin-embedded tissues from 47 cases. The samples comprised reactive lymphoid proliferations of skin, tonsil, and lymph node including dermatopathic lymphadenopathy and Langerhans' cell histiocytosis, Hodgkin's and non-Hodgkin's lymphomas, and thymomas. Interdigitating and dermal dendritic cells, veiled cells, Langerhans' cells, and also cortical thymocytes and their neoplastic counterparts displayed immunostaining with MAb 010 in paraffin sections. These results are identical to previous ones reported for other CD1a MAbs in fresh or frozen specimens. The findings suggest that the binding site of 010 is a fixation-resistant epitope of CD1a antigen which has not been previously identified.

A case of cutaneous B-cell lymphoma with a storiform stromal reaction

A case of cutaneous B-cell lymphoma is described. The patient was treated only by surgical excision of the skin tumors five times during a period of about two years from February of 1984 to October of 1986. After the last surgical excision, a continuous disease-free period was achieved. Biopsy samples showed dense lymphocytic infiltrations with discrete masses in the dermis and subcutis; one of them showed a storiform pattern. At the time, the infiltrating cells were composed of medium and large lymphoid cells and spindle-shaped cells. The medium and large lymphoid cells were positive for CD20, CD22 and HLA-DR and negative for CD3, CD4, CD5, CD8, CD43, and kappa and lambda light chain. The spindle-shaped cells were negative for CD20, CD43, kappa and lambda light chain, lysozyme, and S-100 protein.

A case of cutaneous B-cell lymphoma treated successfully with MACOP-B

A case of cutaneous B-cell lymphoma successfully treated by MACOP-B therapy is described. The patient was a 43-year-old man with reddish tumors measuring 3 to 7 cm in diameter on the right cheek and the post-auricles. Histopathologically, massive infiltrations of medium-sized atypical lymphoid cells were found in the reticular dermis and subcutis. A clear zone beneath the epidermis was also detected. The atypical lymphoid cells were positive for CD19, CD20, CD22 and HLA-DR but negative for CD3, CD4, CD5, CD10, CD43, CD45RO and CDw75. The patient was treated successfully with the MACOP-B protocol from March of 1990 to May of 1990. Since April of 1990, he has been free of disease.

Cutaneous pseudo-T-cell lymphomas. A clinicopathologic study of 20 patients

The histologic features of 20 patients with cutaneous pseudo-T-cell lymphomas other than actinic reticuloid and lymphomatoid papulosis were investigated. Two histologic types of cutaneous pseudo-T-cell lymphomas were designated. The band-like (MF-like) pattern that simulated mycosis fungoides (MF) and a nodular pattern that mimicked cutaneous T-cell lymphomas (CTCL) other than MF. Both patterns showed histologic features that generally are not found in CTCL and thus may be helpful in the differential diagnosis from CTCL. However, at present the differential diagnosis between pseudo-T-cell lymphomas and CTCL should be based on a combination of clinical and histologic data.