Cutaneous Involvement in Multiple Myeloma: Title and subTitle BreakA Clinicopathologic, Immunohistochemical, and Cytogenetic Study of 8 Cases FREE

THERE ARE 4 types of plasma cell neoplasia: classic multiple myeloma (MM), extramedullary plasmacytoma without MM, solitary plasmacytoma of bone, and plasma cell leukemia. Cutaneous involvement may be seen in all 4 types of plasma cell neoplasia. Primary cutaneous plasmacytoma is very rare, and the most common specific cutaneous involvement by plasma cell neoplasia is the result of direct extension to the skin from underlying bony osteolytic lesions of MM or solitary plasmacytoma of bone. Although soft tissue involvement of the upper airway and oral cavity is frequently seen in patients with classic MM and extramedullary plasmacytoma, metastatic skin lesions without underlying bony involvement are very rare. Our literature review of cases with secondary cutaneous involvement in MM and extramedullary plasmacytoma, including cases of direct extension to the skin from adjacent bony lesions and cutaneous metastases in the absence of underlying osseous lesions,^{1 - 59} is summarized in Table 1.

Herein we report the clinicopathologic features of 8 patients with cutaneous involvement by MM that were not the result of direct extension from underlying bone lesions. We reviewed all previously reported cases of cutaneous involvement secondary to MM and extramedullary plasmacytoma with particular attention to the immunoglobulin and the light-chain types, the therapy, and the survival once cutaneous metastases were detected. Cases described in the literature as primary cutaneous plasmacytomas were not included in this review.

A 75-year-old woman was diagnosed in May 1999 as having IgA MM. She received chemotherapy with vincristine, carmustine, doxorubicin, dexamethasone, cyclophosphamide, and melphalan with partial response. The disease continued to progress, and in June 2000 a course of intensive chemotherapy was followed by autologous transplantation of blood progenitor cells. In May 2001, multiple nodular lesions appeared on the lower back (Figure 1), and a skeletal survey revealed widespread osteolytic lesions. New courses of aggressive chemotherapy and radiotherapy were administered. In spite of this treatment, the disease progressed with clinical deterioration, and the patient died in January 2002, 7 months after the development of cutaneous involvement.

A 73-year-old man was diagnosed as having IgA MM in April 1999. A skeletal survey disclosed multiple osteolytic lesions on the skull, jaw, and right humerus. Treatment with melphalan and prednisone was initiated, and the condition improved. In November 2000, the patient became unresponsive to this therapy and experienced clinical and hematologic progression of the disease. The patient received chemotherapy with cyclophosphamide, melphalan, erythropoietin, and dexamethasone, but numerous erythematous nodules arose on the right anterior portion of his chest (Figure 2). His condition progressively deteriorated, and he died in January 2001, a few days after the onset of the skin lesions.

A 70-year-old man reported weakness and severe bone pain. Serum protein electrophoresis, bone marrow aspirate, biopsy specimens, and skeletal survey demonstrated IgG MM. The patient was treated with combined chemotherapy with vincristine, carmustine, melphalan, cyclophosphamide, and dexamethasone. One year later, multiple erythematous nodules appeared on the scalp and the skin of the abdomen. The patient received treatment with dexamethasone and experienced regression of the cutaneous nodules, but he died 1 month later.

A 59-year-old woman was diagnosed as having IgA MM and received chemotherapy with melphalan and prednisolone. One year after diagnosis, she presented with multiple skin nodules and livid plaques on her abdomen and lower trunk. Chemotherapy was initiated with melphalan and prednisolone, but the patient died 6 months later.

A 75-year-old woman presented with multiple skin nodules on the abdomen. No evidence of systemic disease was found at the time of presentation. Histopathologic study of these lesions demonstrated nodular collections of neoplastic plasma cells involving the entire dermis. Eight months later, a diagnosis of IgA MM was established on the basis of hematologic, bone marrow, and radiologic studies. The patient was lost to follow-up.

A 70-year-old woman with a diagnosis of IgA MM presented in June 2000 with scattered papular violaceous lesions on her trunk. The diagnosis of MM had been made by the presence of multiple lytic bone lesions and the findings of a bone marrow biopsy. The patient was treated with melphalan and prednisolone. Despite treatment, she died 2 months after presentation with cutaneous involvement.

A 72-year-old man with a diagnosis of IgG MM presented with numerous papules and nodules on the abdomen. The diagnosis of myeloma had been made 1 year before by the presence of lytic lesions on skull and spine and the findings of serum protein electrophoresis and bone marrow biopsy. At presentation, treatment consisted of cyclophosphamide and melphalan. He died 3 months after presentation.

A 49-year-old man with a diagnosis of IgA presented with prominent periorbital edema and multiple violaceous skin nodules on the upper limbs. The diagnosis of MM was made by the presence of multiple lytic bone lesions and findings from serum protein electrophoresis and a bone marrow biopsy. The patient was treated with combined chemotherapy and died 3 months after the diagnosis of cutaneous involvement.

Tissue sections from skin lesions of each patient were stained with hematoxylin-eosin. Immunohistochemical studies were performed on formalin-fixed, paraffin-embedded tissue using the standard avidin-biotin technique.⁶⁰ The antibodies used in this study, their sources, and their dilutions are listed in Table 2.

In 3 cases in which there was available tissue after histopathologic and immunohistochemical studies (cases 2, 3, and 4), polymerase chain reaction (PCR) investigations for IgH immunoglobulin genes, human herpesvirus 8 (HHV-8), and Epstein-Barr virus (EBV) were performed. For DNA isolation, four to ten 10-µm sections of the paraffin-embedded formalin-fixed samples were deparaffinized with xylene and ethanol and digested with 0.6 mg of proteinase K overnight. The DNA was purified by the QIAamp DNA Mini Kit (Qiagen, Hilden, Germany) and extracted with 150 µL of Tris-EDTA buffer. The presence of DNA subject to amplification was identified using a PCR specific for the factor V gene.

Monoclonality analysis for IgH was performed with 50µM of the following frame 3–specific primers: FR3, 5′-ACACGGCYGTRTATTACTGT-3′, and fluorescent (Cy-5–labeled) JH, 5′-ACCTGAGGAGACGGTGACC-3′. Tissue from a high-grade B-large-cell lymphoma of the lower leg (European Organization for Research and Treatment of Cancer [EORTC] classification) was used as positive control. Polymerase chain reaction was performed with 1.5mM magnesium chloride, 50mM potassium chloride, 10mM Tris hydrochloride (pH = 9.0), 200mM of each of the dinucleotide triphosphates, and 1.5 U of recombinant Taq DNA polymerase in a final volume of 25 µL under the following conditions: 20 seconds at 94°C, 20 seconds at 62°C, and 20 seconds 72°C for 33 cycles. After denaturation for 2.5 minutes at 85°C, all samples were loaded on a denaturing gel (ReproGel High Resolution; Amersham Biosciences, Freiburg, Germany) and run at 55°C and 30 W for 200 minutes. Visualization of the fluorescent-labeled PCR products was performed by a fragment analysis software (Fragment Analyzer; Amersham Biosciences) connected to a laser-based automated sequencer (AlfExpress II; Amersham Biosciences).

For HHV-8, PCR conditions were as follows: 20 seconds at 94°C, 20 seconds at 58°C, and 20 seconds at 72°C for 40 cycles using 80µM of Kaposi sarcoma–associated herpesvirus 1, 5′-AGCCGAAAGGATTCCACCAT-3′, as forward primer and 80µM of Kaposi sarcoma–associated herpesvirus 2, 5′-TCCGTGTTGTCTACGTCCAG-5′, as reverse primer. For EBV, PCR was performed with 50µM of the primers EBV-1, 5′-CGCAGGGATGCCTGGACACA-3′, and EBV-2, 5′-CTGTTTGTGGGCCTTGTGGC-3′. After an initial denaturation step of 3 minutes at 94°C, the samples were run for 30 seconds at 94°C, 30 seconds at 69°C, and 20 seconds at 72°C for 40 cycles. Both viral PCRs were performed with 1.5mM magnesium chloride, 50mM potassium chloride, 10mM Tris hydrochloride (pH = 9.0), 200mM of each of the dinucleotide triphosphates, and 1.5 U of recombinant Taq DNA polymerase in a final volume of 25 µL. All samples were run on ethidium bromide–stained 2% agarose gels and visualized under UV light (302 nm).

Fluorescent in situ hibridization (FISH) studies of the chromosomal deletion of rb-1 (retinoblastoma gene) were performed as described by Kuchinka et al⁶¹ in 3 cases (cases 2, 3, and 4). After deparaffinization of one 50-µm tissue section and incubation with 1 mg of collagenase XI for 2 hours, the sample was incubated with 0.05% trypsin and EDTA for 1 to 2 hours. The nuclei were directly dropped on slides, which were then baked for 2 hours at 50°C. After dehydration, the slides were incubated in pretreatment solution (Appligene Oncor, Heidelberg, Germany) following the instructions of the suppliers and proteinase K (150 µg/mL). After dehydration, the samples were hybridized overnight to the spectrum orange–labeled rb-1 probe (Vysis, Bergisch Gladbach, Germany), washed with 60% formamide and sodium chloride–sodium citrate buffer for 15 minutes at 45°C and counterstained with DAPI (4′,6-diamidino-2-phenylindole). The signals were visualized with an Axioplan 2 microscope (Zeiss, Göttingen, Germany) using a DAPI single-bandpass filter for the identification of the nuclei and a spectrum-orange small bandpass filter for visualization of the signals (Vysis). Samples from normal skin served as positive controls.

The clinical data of our 8 cases are summarized in Table 1. Histopathologically, the skin lesions of these patients showed either a nodular pattern (Figure 3) or a diffuse interstitial pattern (Figure 4). The nodular pattern was seen in 5 cases (cases 2, 3, 4, 5, and 8), the diffuse interstitial pattern in 2 (cases 6 and 7). One case (case 1) showed a combination of nodular and interstitial patterns in the same biopsy specimen. Except for case 7, in which only focal involvement of the dermis was seen, the remainder of cases showed involvement of the entire thickness of the dermis. In all cases, the epidermis was spared, and most of them showed a thin band of uninvolved papillary dermis. The infiltrate extended to subcutaneous tissue in 3 cases (cases 1, 5 and 8).

The nodular pattern consisted of single or multiple clusters of neoplastic plasma cells arranged in relatively cohesive masses. In contrast, the diffuse interstitial pattern was characterized by strands and narrow cords of neoplastic plasma cells arranged between collagen bundles. In some cases, the neoplastic cells were readily identified as plasma cells with variable maturation, and some of them were binucleated or multinucleated. Other cases, however, showed large cells with pleomorphic vesicular nuclei, prominent nucleoli, and granular eosinophilic cytoplasm, and they were often difficult to identify as plasmablasts. In case 6, the neoplastic plasma cells were spindle shaped, resulting in a sarcomatoid appearance (Figure 5). In cases in which the infiltrate was predominantly composed of immature plasmablasts, mitotic figures were frequently seen, including many atypical forms. No Russell or Dutcher bodies were identified.

Immunohistochemical studies demonstrated that the neoplastic cells showed strong immunoexpression for CD79a, CD138 (Figure 3F), and epithelial membrane antigen (Figure 3G), and variable immunoreactivity for VS38c and CD43. In case 3, neoplastic plasma cells expressed CD56 antibody, but this marker was negative in the other cases. All other markers were negative in all cases. In all cases, neoplastic plasma cells secreted immunoglobulins. As expected, in each case the immunoglobulin profile and the light-chain type expression of the cells in the cutaneous lesions correlated with the serum immunoelectrophoresis studies (eg, case 2, Figure 3C-E), supporting the neoplastic nature of the dermal plasma cells. In cases 2, 3, and 4, PCR investigations revealed monoclonal rearrangement for IgH genes (Figure 6), whereas the investigations for HHV-8 and EBV yielded negative results. The FISH analysis revealed rb-1 deletion in cases 2, 3, and 4 (Figure 7).

Review of the literature regarding specific cutaneous involvement in MM is difficult to interpret because some cases were reported as part of series where individual details were missing, and other cases were published in very old reports. Most authors accept that it was Bruno Bloch¹ who first reported specific skin involvement in MM in 1910. This report, however, described

a man who had small reddish macules that evolved into yellowish or brown-reddish small papules or nodules with scale crusts. These skin lesions appeared in consecutive eruptions and in disseminated array on the whole body including the trunk, thighs, and arms. Lesions disappeared spontaneously, leaving scarlike atrophies and depigmentation. Recurrent episodes of these cutaneous lesions presented for many years. Histologically, the lesions showed epidermal necrosis (dense, adjacent, round-cell infiltrate with only a few plasma cells). When the patient was 67 years old, Bence-Jones protein was detected in the urine, and multiple osteolytic lesions appeared in the right humerus, several ribs, and many vertebrae. He died 2 years later with multiple myeloma and metastases in the pleura, stomach, and heart.¹

Although this patient obviously had MM, the clinicopathologic description of the cutaneous lesions is more consistent with a diagnosis of either pityriasis lichenoides or lymphomatoid papulosis rather than cutaneous involvement by MM. In spite of that, if we accept as authentic cases all reports of cutaneous involvement by MM, a review of the literature reveals 100 described cases, including the 8 cases of the present series (Table 1). Clinical data are specified in 87 cases: there were 63 men and 24 women. The age range of the patients was 36 to 81 years (median, 60 years). Skin lesions appeared in the form of papules or cutaneous and subcutaneous nodules that measured 1 to 5 cm in diameter, with firm consistency, smooth surface, and a red or violaceous color. Sometimes larger lesions were present, and plaques rather than nodules have also been described. Ulceration and secondary infection of the cutaneous lesions sometimes occurred.³⁴ Some patients presented with solitary lesions, but multiple nodules were almost always present. Cutaneous involvement by MM may appear in any area of the skin, but it has been reported most commonly on the trunk and abdomen (65 patients), followed by the scalp, face, and neck (27 patients), lower extremities (23 patients), and upper extremities (16 patients).

Some authors have proposed that cutaneous involvement in MM only occurs when the total body tumor cell mass has reached the high-risk size of 2 to 3 kg.¹⁹ Although skin lesions may develop early in the course of the disease or even be the first manifestation of the disease,^{3 ,29 ,48 ,55} cutaneous involvement in patients with MM and extramedullary plasmacytoma generally appears late in the course of the disease. Moreover, most patients have extensive tumor burden, and this should be considered a sign of poor prognosis. Despite the fact that some patients have survived for several years after developing cutaneous involvement by MM,^{8 ,10 ,31 ,34 ,36 ,43} on average, death of most patients occurred within 12 months after the diagnosis. At autopsy, most patients have extensive plasmacytic infiltration of multiple organs.

A review of the cases of MM involving the skin reveals that immunoglobulin type was well characterized in 74 cases: 40 cases were IgG (20 cases κ, 7 cases λ, and 13 cases with no description of the type of light chain); 21 cases were IgA (4 cases κ, 10 cases λ, and 7 cases with no described light chain type); 9 cases were IgD (5 cases λ and 4 cases with no described light chain type); 1 case was IgM (no description of the type of light chain), and 3 cases showed only Bence-Jones protein in the urine. From these data, it is apparent that the risk of cutaneous involvement by MM is not associated with a particular class of myeloma immunoglobulins. Although some authors have described a higher than expected incidence of IgA subtype,³⁴ a review of the literature reveals that IgG MM is the most frequent subtype associated with skin involvement, probably an expression of the numerical predominance of this subtype among the patients with MM. A more aggressive biological behavior has been described in patients with cutaneous involvement by IgD MM and disease with light-chain subtypes only.^{17 ,34}

Histopathologically, the lesions of MM involving the skin show 2 patterns: nodular and diffuse interstitial.³⁴ In our experience, the nodular pattern is more frequent than the interstitial pattern, and often the preexisting normal adnexal structures of the dermis are obliterated and destroyed by the neoplastic plasma cells. In a minority of cases, the cells involving the dermis appear as mature-looking plasma cells, with "clock-face" nuclear chromatin. More often, however, the morphologic features of the neoplastic plasma cells are not typical, and they consist of immature forms with dispersed chromatin, a high nuclear-cytoplasmic ratio, and prominent nucleoli. These immature plasmablasts may be seen in the cutaneous lesions even when the bone marrow findings are typical of multiple myeloma, with predominance of mature plasma cells.¹⁷

In rare instances, as in our case 6, the neoplastic plasma cells may show a spindle-shaped appearance that adds to the difficulties in interpretation. For example, cutaneous, spindle-cell B-cell lymphomas have been recently described.^{62 - 63} However, neoplastic cells of these cases of spindle-cell B-cell lymphoma expressed the pan–B-cell marker CD20, whereas this marker was not present in our case of cutaneous involvement by MM showing spindle-cell morphology of neoplastic cells. In those cases with a diffuse interstitial pattern showing narrow cords of neoplastic cells between collagen bundles of the dermis, a histopathologic differential diagnosis with leukemia cutis should be established. However, in our cases this differential diagnosis was straightforward because immunohistochemical staining with myeloperoxidase was negative in all cases.

From an immunohistochemical point of view in our series, because of the limited number of available slides in some cases and the different types of fixation used from the different institutions, our results must be interpreted with caution. However, in our cases neoplastic plasma cells of MM involving the skin showed a fairly homogeneous immunophenotype characterized by strong immunoreactivity for CD79a, CD138, and epithelial membrane antigen and variable immunoreactivity for CD38 and CD43. All other markers were negative. Usually, neoplastic plasma cells of myeloma lack pan–B-cell antigens CD19 and CD20. In contrast with normal plasma cells, which lack expression of CD43 and CD56, neoplastic plasma cells of MM may show aberrant expression of these 2 markers. In 2 of our cases (cases 1 and 2), there was weak immunoreactivity for CD43, whereas CD56 tested negative in all cases except case 3.

The collagen-1 binding proteoglycan, syndecan-1 (CD138), has been found to be a specific marker for plasma cells within the bone marrow of patients with MM, and it may be important for plasma cell anchoring in the bone marrow. This marker is not present in other hematopoietic cells or endothelial cells, and it has been suggested that loss of CD138 from the cell surface may contribute to myeloma proliferation and dissemination.⁶⁴ In our cases, however, neoplastic plasma cells involving the skin expressed strong immunoreactivity for CD138, and it remains to be demonstrated whether CD138 immunoexpression is related to prognosis. Regarding the immunoglobulin type, in all patients of our series there was a perfect correlation of immunoglobulin and light-chain type between the serum electrophoresis and the plasma cells involving the skin.

The finding of HHV-8⁶⁵ and EBV⁶⁶ genomic sequences by PCR in neoplastic plasma cells of MM has been reported mostly in patients with acquired immunodeficiency syndrome (AIDS), raising the possibility that the emergence of EBV- or HHV-8–immortalized B cells may have a primary function in the pathogenesis of plasma cell tumors in patients with AIDS. Three of our cases were studied by PCR for genomic material of HHV-8 and EBV, and all 3 cases proved negative. This suggests that neither HHV-8 nor EBV has a role in plasma cells neoplasms in patients who test negative for the human immunodeficiency virus.

There is increasing evidence for an important role of cytogenetics in determining the prognosis of patients with MM. Deletion of 13q and 11q aberrations in neoplastic plasma cells have been regarded as unfavorable cytogenetic features in patients with MM treated by tandem autotransplantation.^{67 - 68} Furthermore, a recent study⁶⁹ has used FISH techniques to demonstrate that bone marrow plasma cells from 89 previously untreated patients with MM and the rb-1 deletion were associated with poor response to induction treatment and more aggressive clinical course. We used the same technique to study the rb-1 deletion in the skin biopsy specimens from 3 patients with cutaneous involvement in our series, and all showed this deletion. Skin involvement is a well-known indicator of poor prognosis in MM, and the rb-1 deletion only corroborated it, but it is possible that this cytogenetic abnormality may be helpful in identifying high-risk patients with earlier-stage MM that demonstrates aggressive biological behavior and poor response to chemotherapy.

In conclusion, cutaneous involvement by MM occurs infrequently. Histopathologic and immunohistochemical studies have proved to be valuable adjuncts to confirm the neoplastic nature of the plasma cells involving the skin because of their monotypic expression of immunoglobulin light chain. Cutaneous involvement by plasma cell neoplasms usually heralds a poor prognosis regardless of the various forms of therapy. Innovative cytogenetic techniques such as demonstration of the rb-1 deletion may provide useful information to define high-risk patients with MM.

Corresponding author and reprints: Luis Requena, MD, Department of Dermatology, Fundación Jiménez Díaz, Avda Reyes Católicos 2, 28040-Madrid, Spain (e-mail: lrequena@fjd.es).

Accepted for publication November 20, 2002.