KP1/CD68 expression in malignant neoplasms including lymphomas, sarcomas, and carcinomas

Histomorphological Evidence of Complex Cannibalism-An Uncharted Territory in Oral Squamous Cell Carcinoma

Complex cannibalism (CxC) is an emerging new seeming entity in oral squamous cell carcinoma (OSCC) embody as a prime metabolic event in determining the aggressive potential. Owing to paucity in literature regarding it, the aim of the present study to deciphering the occurrence of CxC in OSCC. Further, the expression of cluster of differentiation 68 (CD68) was studied in tumor cells and correlated with CxC to ascertain the biological behaviour of OSCC. 30 Hematoxylin and Eosin stained sections of various grades of OSCC were scanned for CxC and correlated with clinicopathological parameters. Immunohistochemical analysis using CD68 was performed. While observing CxC in OSCC, statistically significant in age (p-0.048) and histological grades (p-0.004). CD68 expression in tumor cells was statistically significant in histopathological grades (p < 0.001) whereas on correlating with CxC (p - 0.171) was non-significant. The analogous rise in CxC and CD68 with increasing histopathological grades could aid in recognising CxC as a precise histopathological parameter to assess the aggressive biological potential in OSCC.

Expression of Melan-A in cutaneous granular cell tumours: a diagnostic pitfall

Morphological overlap exists between cutaneous granular cell tumours (GCT) and malignant melanoma, with the melanocyte-specific markers HMB45 and Melan-A commonly used to support the diagnosis of melanoma. We recently encountered several cases of GCT in our practice showing strong expression of Melan-A. The aim of this study was to establish the prevalence of positive immunohistochemical staining for Melan-A and HMB45 in a series of unequivocal GCTs. We also aimed to assess the prevalence of staining for PRAME (PReferentially expressed Antigen in MElanoma), a marker expressed in >80% of primary melanomas as well as many non-melanocytic tumours. A total of 20 cutaneous/subcutaneous GCTs were evaluated using Melan-A, HMB45 and PRAME immunohistochemistry. Staining for Melan-A and HMB45 was scored using a semiquantitative scale from 0 (absent) to 3+ (staining present in >50% of tumour cells). PRAME expression was recorded as either positive (>75% of cell nuclei staining) or negative. Melan-A expression was observed in four GCTs (20%), with strong and diffuse (3+) staining seen in two cases (10%), both from anogenital areas. Weak patchy nuclear PRAME expression was seen in every case, interpreted to be negative. HMB45 was also negative in all cases (100%). Our study demonstrates that Melan-A expression can be strong and diffuse in a subset of otherwise unequivocal cutaneous GCTs, which may cause diagnostic confusion with malignant melanoma. HMB45 and PRAME did not stain any of the GCTs in our series.

Signet-ring cell sinus histiocytosis: report of the clinicopathologic characteristics of 4 cases with emphasis on the differential diagnosis of signet-ring cell lesions

Signet-ring cell sinus histiocytosis (SRCSH) represents a distinctly rare reactive phenomenon predominantly affecting axillary and pelvic lymph nodes (LNs) of individuals with breast or prostatic adenocarcinoma. Reports of SRCSH in the literature are sparse with only 12 previous examples, thus underscoring the rarity of this process. Here, we report 4 additional SRCSH cases affecting 2 women and 2 men (M/F = 1:1; age range: 50-71 years; mean age = 61 years). In the 2 men, pelvic LNs were excised during radical cystoprostatectomy for genitourinary cancer, whereas in one woman, SRCSH was incidentally discovered in axillary LNs during mastectomy for breast adenocarcinoma. The other female patient presented with a history of aortic valve replacement and enlarged supraclavicular LNs. Microscopically, all involved LNs exhibited marked distention with filling of the subcapsular and medullary sinuses by sheets of signet-ring histiocytes containing a singular large, cytoplasmic vacuole and a crescentic nucleus. Overt cytologic atypia, pleomorphism, and mitoses were absent. Erythrophagocytosis and occasional fibrosis were appreciated. None of the LNs with SRCSH showed evidence of metastatic tumor. Immunohistochemically, signet-ring sinus histiocytes were invariably positive for CD68 and CD163 but were negative for pancytokeratins. The histopathologic characteristics of SRCSH, albeit bland, in conjunction with the patient's medical history, may be misinterpreted as metastatic adenocarcinoma with signet-ring cell configuration. Immunohistochemical confirmation of the histiocytic lineage of the lesional cells in SRCSH usually suffices for rendering an accurate diagnosis. The underlying pathogenetic mechanism and possible biologic significance of SRCSH remain currently unknown.

Plexiform fibrohistiocytic tumor: a clinicopathological and immunohistochemical study of 39 tumors, with evidence for a CSF1-producing "null cell" population

Plexiform fibrohistiocytic tumor (PFHT) is a mesenchymal tumor of intermediate malignancy, typically occurring in the superficial soft tissues of young patients and displaying a biphasic pattern, with nodules of histiocytoid cells surrounded by fascicles of myofibroblastic spindled cells. The pathogenesis of PHFT is unknown. We comprehensively studied 39 PFHT, occurring in 25 females (66%) and 13 males (34%), ranging from 2 to 55 years of age (median 21 years). The tumors most often occurred in the upper extremity (n = 16, 41%) and ranged from 0.4 to 6.1 cm in size (median 1.5 cm). One patient with known neurofibromatosis type 1 presented with metachronous tumors of the finger and back. Clinical follow-up (29 patients; range 5-168 months; median 60 months) showed 3 tumors to have recurred locally; none was metastasized. One patient died of an unrelated cause; all others were alive without disease at the time of last follow-up. Immunohistochemistry showed the histiocytoid nodules of all cases to contain CD163/CD11c-positive histiocytes and cells negative for both markers ("null cells"). CSF1 expression was present in "null cells" in 7/10 cases (RNAscope chromogenic in situ hybridization). The Ki-67 labeling index was very low (< 5%); Ki-67-positive cells within histiocytoid nodules appeared to represent "null cells." All tested cases were negative for significant mutations or fusion events (TruSight Mutation Panel, TruSight Fusion Panel, Mayo Clinic Melanoma Targeted Gene Panel). We conclude that PHFT may be even more indolent than has been appreciated, although classification as an "intermediate" tumor is correct. We hypothesize that the CSF1-producing "null cells" of PHFT may represent the neoplastic element, with the bulk of the tumor masses comprising recruited and reactive cell populations.

PD-L1 near Infrared Photoimmunotherapy of Ovarian Cancer Model

(1) Background: Despite advances in surgical approaches and drug development, ovarian cancer is still a leading cause of death from gynecological malignancies. Patients diagnosed with late-stage disease are treated with aggressive surgical resection and chemotherapy, but recurrence with resistant disease is often observed following treatment. There is a critical need for effective therapy for late-stage ovarian cancer. Photoimmunotherapy (PIT), using an antibody conjugated to a near infrared (NIR) dye, constitutes an effective theranostic strategy to detect and selectively eliminate targeted cell populations. (2) Methods: Here, we are targeting program death ligand 1 (PD-L1) using NIR-PIT in a syngeneic mouse model of ovarian cancer. PD-L1 PIT-mediated cytotoxicity was quantified in RAW264.7 macrophages and ID8-Defb29-VEGF cells in culture, and in vivo with orthotopic ID8-Defb29-VEGF tumors. (3) Results: Treatment efficacy was observed both in vitro and in vivo. (4) Conclusions: Our data highlight the need for further investigations to assess the potential of using NIR-PIT for ovarian cancer therapy to improve the treatment outcome of ovarian cancer.

Distinguishing melanophages from tumor in melanoma patients treated with talimogene laherparepvec

Response to talimogene laherparepvec (T-Vec) is difficult to assess as pigmented macrophages that have ingested melanoma cells ('melanophages') persist after injection, mimicking melanoma. We used quantitative immunofluorescence (qIF) to (1) distinguish melanophages from melanoma in biopsies from two patients treated with T-Vec and (2) evaluate the tumor microenvironment pretreatment and posttreatment. Tissues were stained with 4',6-diamidino-2-phenylindole, cluster of differentiation (CD) 3, CD8, CD68, human leukocyte antigen-DR isotype (HLA-DR), and SRY-Box Transcription Factor 10 (SOX10), and multispectral images were analyzed. Post-T-Vec samples showed melanophages with cytoplasmic costaining of CD68, SOX10, and HLA-DR, without nuclear SOX10 expression. qIF revealed a dense immune infiltrate of CD3, CD8, and CD68 cells in post-T-Vec samples. Melanophages from tumors post-T-Vec stain the nuclear melanoma marker SOX10 in their cytoplasms as compared to melanoma cells that stain nuclear SOX10. This novel finding highlights the phagocytosis of melanoma cell components by macrophages after treatment with T-Vec. qIF may assist pathologists in determining whether lesions treated with immunotherapy contain residual viable melanoma.

Role of CD68 immunohistochemistry in categorizing benign nonmesothelial cell population and refining "atypical" category in serous fluid cytology

BACKGROUND

Body fluids are rich in histiocytes and may mimic atypical epithelial cells morphologically. Histiocytes can pose a significant challenge in serous fluid cytology as they tend to appear atypical due to prolonged accumulation in serous fluids in vivo and processing by liquid-based cytology in vitro. Not many studies have documented the utilization of histiocytic marker such as CD68 in serous fluid cytology, which can subsequently reduce the "atypical" diagnostic category.

METHODS

One thousand one hundred and twenty-nine cases of serous fluid cytology from 2016 to 2019 were reviewed and reclassified based on proposed classification of the international system for reporting serous fluid cytology. There were 133 cases with atypical diagnoses, out of which 51 cases had cellblocks. An immunohistochemistry (IHC) panel, including two mesothelial markers, two epithelial markers, and one histiocytic marker was applied to the atypical samples. Same IHC panel was utilized to evaluate 15 cases each from negative for malignancy (NFM), suspicious for malignancy (SFM), and malignant (MAL) categories for further comparison.

RESULTS

After reevaluation of the cytology material with IHC stains, 924 (82%), 133 (12%), 23 (2%), and 49 (4%) of the cases were reclassified as NFM, atypia of uncertain significance, SFM, and MAL, respectively. Twenty-five out of 51 atypical cases (49%) were downgraded to "benign" after reevaluation with CD68 IHC.

CONCLUSION

Histiocytes can mimic atypical epithelial cells in body fluids. Effective utilization of CD68 IHC will be beneficial in further refining the "atypical" diagnostic category in serous fluid cytology.

Histiocytic Sarcoma: Review, Discussion of Transformation From B-Cell Lymphoma, and Differential Diagnosis

Context.—

Histiocytic sarcoma is a rare neoplasm of mature histiocytes with an aggressive clinical course that can arise de novo or from a low-grade B-cell lymphoma. In particular, chronic lymphocytic leukemia/small lymphocytic lymphoma is a very common malignancy in the Western hemisphere, and most cases of chronic lymphocytic leukemia/small lymphocytic lymphoma have an indolent course and behavior. However, 2% to 8% of chronic lymphocytic leukemia/small lymphocytic lymphoma cases transform. Histiocytic sarcomatous transformation is rare and portends poor prognosis.

Objective.—

To review the clinical features, morphology, and key points related to the differential diagnosis for histiocytic sarcoma. We discuss recent understanding of the biology underlying transformation.

Data Sources.—

University of Michigan case and review of pertinent literature about histiocytic sarcoma and morphologic differential diagnosis.

Conclusions.—

Histiocytic sarcoma is a rare histiocytic neoplasm that can arise as a result of transdifferentiation from low-grade B-cell lymphomas, and has a wide differential diagnosis including other histiocytic/dendritic cell neoplasms, myeloid neoplasms, lymphomas, melanoma, and carcinoma. However, some key morphologic and immunohistochemical features allow for accurate classification.

Sunitinib-induced morpho-functional changes and drug effectiveness in malignant solitary fibrous tumours

Sunitinib improves the outcomes of patients with solitary fibrous tumours (SFTs). The aim of this study was to investigate and contextualise sunitinib-induced morpho-functional changes in order to gain insights into the drug's mechanism of action.To this end, four surgical specimens obtained from two sunitinib-responsive patients with malignant SFT, and one primary cell culture obtained from fresh tumoral tissue and its stabilised cell line, were studied by means of immunohistochemistry, bright field in situ hybridisation, immunofluorescence/confocal microscopy, and biochemistry.The post-sunitinib surgical samples were characterised by two biologically relevant morpho-functional changes: clear areas and necrotic foci. The first were associated with the attenuation/loss of PDGFRB expression and decreased mTOR signalling, and corresponded to a pathological response. The second were associated with the over-expression of PDGFRB and VEGFA, strong mTOR signalling activation, and the appearance of HIF1α expression, hallmarks of pathological progression. The analysis clearly showed that sunitinib reduces the vascular supply network and inhibits tumoral cells. It also either induces autophagy, thus favouring drug response, or impairs autophagy as a result of lysosome sequestration, thus favouring disease progression. These distinct autophagic events were associated with different myeloid immune contextures. Finally, we also found that PDGFRB is one of the components of a complex that includes Beclin 1 and VPS34.The results of these tissue-based analyses provide new insights into sunitinib's mechanism of action in SFT patients.

Clinicopathological correlation of tumor-associated macrophages in Ewing sarcoma

AIMS

Tumor-associated macrophages (TAMs) are known markers playing complex roles in tumorigenesis. However, the function of TAMs in a variety of malignancies is not yet fully understood. The aim of this pilot study was to quantify the density of TAMs in Ewing sarcoma and to determine the correlation between TAMs and clinicopathological parameters.

METHODS

Using immunohistochemistry, the expressions of CD68 and CD163 were examined in 24 tissue samples of Ewing sarcoma of bone. The density of CD68 and CD163-positive TAMs was analyzed quantitatively and semi-quantitatively and statistically correlated with clinical parameters.

RESULTS

CD163-positive TAMs outnumbered CD68-positive cells (median of 130 vs 96, respectively). No statistically significant relatio nship was found between density of CD68-positive cells, clinical parameters or prognosis. However, high levels of CD163-positive TAMs were associated with localized disease (P=0.008). In cases with a higher density of CD163-positive cells, a trend toward longer survival was revealed (P=0.063).

CONCLUSION

This is the first study that has quantified CD163 expression in TAMs in Ewing sarcoma and showed its possible prognostic value. CD163 was confirmed to be a more specific marker of macrophages than CD68. CD163 is not an exclusive hallmark of M2 macrophages.

Spindle Cell Melanoma and Interdigitating Dendritic Cell Sarcoma: Do They Represent the Same Process?

Intranodal spindle cell lesions on biopsy are problematic for a surgical pathologist, often requiring an extensive immunohistochemical evaluation with variable and frequently unsatisfactory results. In the absence of a history of malignancy, the differential diagnosis of a spindle cell tumor must include both a primary nodal proliferation and a metastatic process. Particularly challenging are those lesions that share morphologic and immunohistochemical features; spindle cell melanomas (SCM) and interdigitating dendritic cell sarcomas (IDCS) belong to this category. At present, electron microscopy is the only method proposed to distinguish between the 2 entities; however, this method is often unavailable and impractical. In this study, we assessed the comparative immunophenotypes of 18 cases of SCM and 8 cases of IDCS, with particular emphasis on the expression of MUM-1, β-catenin, SOX-10, MiTF, and p75. Our results showed nearly equivalent staining patterns and profiles; 12% and 17% of IDCS and SCM were labeled for MUM-1, 75% and 83% stained for β-catenin, 0% and 24% expressed MiTF, and 100% and 94% labeled for p75, respectively. All cases of IDCS and SCM displayed strong nuclear reactivity for SOX-10. On the basis of our study and pertinent literature, the morphologic and immmunophenotypic features of SCM and IDCS appear to be virtually indistinguishable from one another, raising the question as to whether these 2 entities represent a pathobiologically similar or even identical process.

Endocytosis of keratinocytes in oral squamous cell carcinoma

Objectives:

To quantify endocytosis of keratinocytes (EK) in oral squamous cell carcinoma (OSCC) and correlate it with different clinical and histopathological parameters. Further, the expression of cluster of differentiation 68 (CD68) and lysozyme was studied in tumor cells to corroborate this phenomenon.

Materials and method:

EK per high-power field (HPF) was calculated on hematoxylin and eosin-stained sections and correlated with clinical and histopathological parameters. CD68 and lysozyme were studied in tumor cells using immunohistochemistry.

Results:

The mean EK per HPF was higher in stage IV (4.450 ± 2.241) than stage III (3.333 ± 1.543) OSCC ( p = 0.1978). Although there were more EK in N2 stage (4.362 ± 0.3405) as compared to N0–N1 (3.462 ± 0.4178), the results were statistically insignificant. Statistically significant difference in mean EK was observed in all the grades of OSCC: well versus moderate ( p = 0.0052), moderate versus poor ( p < 0.0001), and well versus poor ( p = 0.0001). There were significant differences in the mean EK ( p < 0.05) between different grades of stromal degenerations (mild: 2.654 ± 1.093, moderate: 5.115 ± 1.774, and severe: 7.250 ± 2.217). Statistically significant differences were observed in CD68 expression in tumor cells of various TNM stages ( p = 0.049), histopathological grades ( p = 0.045), and stromal degeneration ( p = 0.024). Likewise, lysozyme expression in tumor cells was also statistically significant in histopathological grades ( p = 0.004) and mean EK value ( p = 0.0119).

Conclusion:

The mean EK in OSCC increases with increasing histopathological grades, TNM stages, and stromal degeneration. CD68 and lysozyme can be used as markers of EK in OSCC.

Selected benign cutaneous lesions that may simulate melanoma histologically

As cutaneous melanomas manifest a wide spectrum of clinical and pathologic presentations, several other lesions enter into their differential diagnosis. This article considers those entities, including melanocytic hyperplasia, cellular nodules in congenital nevi, atypical lentiginous melanocytic proliferations, "special site" nevi, epithelioid histiocytoma, neurothekeoma, cellular schwannoma, and proliferating scars.

CD68 expression is a discriminative feature of indolent cutaneous CD8-positive lymphoid proliferation and distinguishes this lymphoma subtype from other CD8-positive cutaneous lymphomas

BACKGROUND

Indolent cutaneous CD8+ lymphoid proliferation is a recently described rare entity among cutaneous T-cell lymphomas that typically presents with solitary skin lesions at acral sites. Separation from otherwise aggressive T-cell lymphomas bearing a cytotoxic CD8+ phenotype is fundamental to avoid unnecessary harmful treatment. However, up to now, no reliable discriminative marker has been identified.

OBJECTIVES

Motivated by these diagnostic quandaries, we have analyzed a large series of archived formalin-fixed paraffin-embedded (FFPE) specimens of atypical CD8+ cutaneous infiltrates with clear-cut diagnosis and clinical follow-up (n = 44) including five cases of indolent CD8+ lymphoid proliferation by using immunohistochemistry with the aim of obtaining markers predictive of subtype assignment.

RESULTS

We identified exclusive expression of CD68 by lymphoma cells within the subgroup of indolent CD8+ lymphoid proliferation (5/5 cases). Specific CD68 expression in this entity was confirmed by the application of several monoclonal antibodies (KP1, PG-M1, KiM1P) against the CD68 molecule available for FFPE tissue. In contrast, none of the infiltrates of the other CD8+ cutaneous lymphoma entities stained positive for CD68 (0/39).

CONCLUSIONS

Based on these observations, we suggest CD68 as a new discriminative marker which is helpful in distinguishing indolent CD8+ lymphoid proliferation from other CD8+ cutaneous lymphomas in ambiguous cases.

Urine kidney injury molecule-1: a potential non-invasive biomarker for patients with renal cell carcinoma

BACKGROUND

KIM-1 staining is upregulated in proximal tubule-derived renal cell carcinoma (RCC) including clear renal cell carcinoma and papillary renal cell carcinoma, but not in chromophobe RCC (distal tubular tumor). This study was designed to prospectively examine urine KIM-1 level before and 1 month after removal of renal tumors.

PATIENTS AND DESIGN

A total of 19 patients were eventually enrolled in the study based on pre-operative imaging studies. Pre-operative and follow-up (1 month) urine KIM-1 levels were measured. The urine KIM-1 levels (uKIM-1) were then normalized to urine creatinine levels (uCr). Renal tumors were also stained for KIM-1 using immunohistochemical techniques.

RESULTS

The KIM-1-negative staining group included 7 cases, and the KIM-1-positive group consisted of 12 cases. The percentage of KIM-1-positive staining RCC cells ranged from 10 to 100 %, and the staining intensity ranged from 1+ to 3+. In both groups, serum creatinine levels were both significantly elevated after nephrectomy. In the KIM-1-negative group, uKIM-1/uCr remained at a similar level before (0.37 ± 0.1 ng/mg Cr) and after nephrectomy (0.32 ± 0.01 ng/mg Cr). However, in the KIM-1-positive group, elevated uKIM-1/uCr at 1.20 ± 0.31 ng/mg Cr was significantly reduced to 0.36 ± 0.1 ng/mg Cr, which was similar to the pre-operative uKIM-1/uCr (0.37 ± 0.1 ng/mg Cr) in the KIM-1-negative group.

CONCLUSION

Our small but prospective study showed significant reduction in uKIM-1/uCr after nephrectomy in the KIM-1 positive group, suggesting that urine KIM-1 may serve as a surrogate biomarker for kidney cancer and a non-invasive pre-operative measure to evaluate the malignant potential of renal masses.

Simultaneous occurrence of malignant fibrous histiocytoma and hepatocellular carcinoma in cirrhotic liver: A case report

Primary hepatic malignant fibrous histiocytoma (MFH) is rarely encountered. There have been no reports to date of hepatic MFH associated with liver cirrhosis. The presence of liver cirrhosis is considered an adjunctive feature favoring sarcomatoid hepatocellular carcinoma (HCC) in the diagnosis of spindle cell tumors in liver. We describe here a 59-year-old man with liver cirrhosis due to hepatitis B virus infection 20 years ago. On abdominal computed tomography scanning, two distinct hepatic masses were identified in the background of cirrhosis, which had different radiological features from conventional HCC. He underwent segmentectomy for removal of the tumors. The pathological examination of surgically resected specimen revealed the large malignant spindle cell tumor and small conventional HCC. Additional tissue sampling and immunohistochemical stainings demonstrated that the spindle cell tumor was consistent with MFH. On the post-operative follow-up for 21 mo, a round mass showing similar radiological findings for the previous MFH was appeared on the surface of resection margin, suggesting the recurrence. Despite its rarity, hepatic MFH should be considered during differential diagnosis, even in cirrhotic patients, and extensive tissue sampling and immunohistochemical analyses are necessary in the diagnosis of hepatic spindle cell tumors.

Immunohistochemical analysis of monocytic leukemias: usefulness of CD14 and Kruppel-like factor 4, a novel monocyte marker

Detection of monocytic differentiation in myeloid neoplasms by immunohistochemical analysis is challenging owing to a lack of sensitive and/or specific antibodies. We tested the usefulness of immunohistochemical analysis for CD14, an antigen commonly detected by flow cytometry, and Krüppel-like factor 4 (KLF4), a potentially novel marker of monocytic differentiation, in a series of myeloid leukemias, including 53 acute myeloid leukemias with monocytic differentiation. These findings were compared with immunohistochemical findings for CD68 (KP-1), CD34, and CD163 and were also correlated with flow cytometric and enzyme cytochemical results. CD163 and CD14 are the most specific markers of monocytic differentiation, followed by KLF4. CD68, in contrast, is the most sensitive monocytic marker, and KLF4 is also significantly more sensitive than CD14 and CD163. These studies show that KLF4 is another marker of monocytic differentiation and that the combination of CD14 and CD163 can increase the diagnostic sensitivity for monocytic neoplasms.

Expression of macrophage antigens by tumor cells

Macrophages are a heterogeneous cell population of the myeloid linage derived from monocytes. These cells show two different polarization states, M1 and M2 macrophages in response to different micro environmental signals. Tumor associated macrophages (TAM) represent the M2 type and promote tumor progression. These cells express antigens that more or less are specific for macrophages like: CD14, CD68, MAC387, CD163, and DAP12. In a series of recent studies it is shown that cancer cells may express these antigens and CD163, MAC387 and DAP12 may be expressed by e.g. breast cancer cells. Thus, 48% of the breast cancers expressed CD163 that is a scavenger receptor normally expressed by macrophages alone. The corresponding figure for rectal cancer is 31%. The expression of CD163 is correlated to early distant recurrence in breast cancer and local recurrence in rectal cancer and reduced survival time in both conditions. Expression of macrophage antigens in breast- and colorectal-cancers may have a prognostic relevance in clinical praxis. One explanation to these findings is that resemblance with macrophages may indicate a more invasive phenotype due to genetic exchange between the primary tumor cells and associated macrophages. This is further supported by the finding that expression of DAP12, a macrophage fusion receptor, in breast cancer is associated with an advanced tumor grade and higher rates of skeletal and liver metastases and overall shorter distant recurrence free survival. Another explanation to the changed phenotype is a genetic exchange between the cells by exosome-mediated transfer.

The stromal cell marker SPARC predicts for survival in patients with diffuse large B-cell lymphoma treated with rituximab

The cellular composition of the tumor microenvironment may affect survival in diffuse large B-cell lymphoma (DLBCL). We performed immunostains for 2 stromal cell markers, CD68 and SPARC (secreted protein, acidic and rich in cysteine), in 262 patients with DLBCL treated with rituximab and cyclophosphamide, doxorubicin, vincristine, and prednisone (CHOP) or CHOP-like therapies. Patients with any SPARC+ cells in the microenvironment had a significantly longer overall survival, and patients with high SPARC positivity in the microenvironment also had a significantly longer event-free survival. Survival differences were mainly due to the prognostic effect of SPARC+ cells in activated B-cell (ABC)-type DLBCL, with no effect found in the germinal center B-cell-type DLBCL. Of clinical features examined, only the number of extranodal sites was significantly associated with SPARC expression. Multivariate analysis revealed that SPARC expression predicted patient survival independent of the International Prognostic Index or tumor cell of origin. SPARC expression in the microenvironment of DLBCL can be used for prognostic purposes, determining a subgroup of patients with ABC DLBCL who have significantly longer survival. More aggressive chemotherapy protocols should be considered for patients with ABC DLBCL without SPARC+ stromal cells. CD68 expression by cells in the microenvironment did not predict survival.

Clinical history of HIV infection may be misleading in cytopathology

Human immunodeficiency virus (HIV)-infected patients are at an increased risk for developing opportunistic infections, reactive conditions and neoplasms. As a result, a broad range of conditions are frequently included in the differential diagnosis of HIV-related lesions. The clinical history of HIV infection may, however, be misleading in some cases. Illustrative cases are presented in which knowledge of a patient's HIV status proved to be misleading and increased the degree of complexity of the cytologic evaluation. Case 1 involved the fine needle aspiration (FNA) of a painful 3 cm unilateral neck mass in a 38-year-old female with generalized lymphadenopathy. Her aspirate revealed a spindle cell proliferation devoid of mycobacteria that was immunoreactive for S-100 and macrophage markers (KP-1, PGM1). Multiple noncontributory repeat procedures were performed until a final excision revealed a schwannoma. Case 2 was a CT-guided FNA of a positron emission tomography positive lung mass in a 53-year-old man. The acellular aspirate in this case contained structures resembling fungal spore forms that were negative for mucicarmine and GMS stains, as well as cryptococcal antigen immunocytochemistry. A Von Kossa stain confirmed that these pseudo-fungal structures were calcified debris. Follow up revealed multiple calcified lung and hilar node based granulomata. Case 3 involved the cytologic evaluation of pleural fluid from a 47-year-old man with Kaposi sarcoma and recurrent chylous pleural effusions. Large atypical cells identified in his effusion were concerning for primary effusion lymphoma. Subsequent pleural biopsy revealed extramedullary hematopoiesis, documenting these atypical cells as megakaryocytes. These cases demonstrate that knowledge of a patient's HIV status can be misleading in the evaluation of cytology specimens, with potential for misdiagnosis and/or multiple procedures. To avoid this pitfall in the setting of HIV infection, common entities unrelated to HIV infection and artifacts should always be included in the differential diagnosis.

CD163: a specific immunohistochemical marker for acute myeloid leukemia with monocytic differentiation

Acute myeloid leukemias (AMLs) with monocytic differentiation with or without recurring cytogenetic abnormalities have prognostic significance. Therefore, it is important to recognize such cases. Monocytic differentiation is identified by morphology and confirmed by cytochemical stains or flow cytometry. However, the materials for such analyses are not always available (air-dried aspirate smears, touch preparations, fresh cells). Thus, the utility of CD163, a hemoglobin scavenger molecule present on monocytes/macrophages, in identifying a monocytic component in AML in fixed, paraffin-embedded bone marrows was assessed. Using tissue microarrays, 31 cases of AML with monocytic differentiation and 35 cases without monocytic differentiation were evaluated in a blinded fashion for CD163 positivity and compared with CD68. Diagnoses were previously well established using cytochemistry and flow cytometry techniques. CD163 immunoreactivity was seen in 49% of AML cases with and 6% (2/35) without monocytic differentiation. CD68 was positive in 81% of AML cases with and 17% without monocytic differentiation. CD163 showed superior specificity for a monocytic component in AML compared with CD68 (94% vs. 83%). However, the suboptimal sensitivity (49%) limits its utility as a definitive marker of monocytic differentiation if negative in paraffin sections. These findings demonstrate that CD163 is helpful for the evaluation of a monocytic component in AML. When positive, correlation and evaluation for an associated recurring cytogenetic abnormality is warranted.

Expression of CD68 in non-myeloid cell types

CD68, the human homologue of macrosialin, is commonly regarded as a selective marker for human monocytes and macrophages. Its expression is thought to be regulated by a macrophage-specific promoter. However, several immunohistochemical studies have indicated that CD68 antibodies also react with other haematopoietic and non-haematopoietic cell types. We investigated the expression of CD68 in various primary cells and carcinoma cell lines using immunohistochemistry, flow cytometry, Western blot analysis and qRT-PCR. Weak but significant immunoreactivity was detected in lymphocytes and several tumour cell lines whereas staining of primary fibroblasts and endothelial cells was comparable to macrophages. The intensity of CD68 staining in individual cell types depended on the antibody clone and the fixation technique. Anti-CD68 mAb KP1 should be used with great caution for frozen tissue sections due to its reactivity with a wide variety of cell types. Also, care should be taken when distinguishing macrophages from fibroblasts/stromal cells in paraffin sections after formalin fixation since both cell types are stained highly positive for CD68. In accordance, mRNA expression of CD68 was not only detected in macrophages and monocytes but also in fibroblasts as well as endothelial cells and tumour cells, although with a varying intensity. Cloning of full length 5'-sequences and determination of transcription start sites shows that macrophages and fibroblasts initiate transcription within the known promoter region; however, from different start sites, indicating alternative promoter architecture in myeloid versus non-myeloid cells. We suggest that CD68 is not a selective macrophage marker but rather a lysosomal protein that is enriched in macrophages.

Best practices in diagnostic immunohistochemistry: pleomorphic cutaneous spindle cell tumors

CONTEXT

Pleomorphic cutaneous spindle cell tumors can be difficult to distinguish solely on histologic grounds. The use of ancillary immunohistochemical studies can greatly assist in this differential diagnosis.

OBJECTIVE

To review histologic and immunohistochemical aspects of cutaneous spindle cell tumors and discuss a basic panel of markers to assist in the differential diagnosis.

DATA SOURCES

English-language literature published between 1981 and 2005.

CONCLUSIONS

A basic immunohistochemistry panel for high-molecular-weight cytokeratin, melanocytic markers (S100 protein, HMB-45, Melan-A), smooth muscle actin, desmin, and endothelial markers (CD31, CD34) is effective in diagnosing most cutaneous spindle cell tumors.

HMB-45 and Melan-A are Useful in the Differential Diagnosis Between Granular Cell Tumor and Malignant Melanoma

Granular cell tumors (GCTs), especially if atypical or malignant, may share cytomorphologic and architectural features with malignant melanoma, when the latter shows granular cell change. In many cases, these neoplasms can be differentiated from each other on histologic grounds, but distinction may sometimes be challenging. By immunohistochemistry, both tumors are strongly positive for S-100 protein and frequently express other nonspecific markers such as CD68, NSE, and NKIC3. In the current study, we reviewed 60 cases of conventional cutaneous, mucosal, and visceral GCT and studied the use of immunoperoxidase staining for the differential diagnosis between malignant melanoma and GCT. Immunohistochemical stains for S-100 protein, A, HMB-45, and microphthalmia transcription factor (MITF) were performed in all cases. All of the tumors were positive for S-100 protein. MITF immunostaining was diffusely positive in 53 (88%) cases, focally positive in three (5%) cases, and negative in four (7%). Fifty-seven (95%) tumors were negative for Melan-A, one case was focally positive, and two cases showed rare positive tumor cells. None of the tumors expressed HMB-45. In conclusion, GCT and malignant melanoma can be reliably differentiated on the basis of immunohistochemical stains in the majority of cases. Although not always positive in malignant melanoma, in this context, HMB-45 expression seems to be 100% specific for the diagnosis of melanoma. Melan-A is slightly less specific, with rare cases of GCT showing focal positivity. MITF is not useful in this differential-93% of the GCTs in our series showed nuclear reactivity for this marker. The latter finding highlights the limited specificity of this antibody in the diagnosis of melanocytic tumors.

Extranodal histiocytic sarcoma: clinicopathologic analysis of 14 cases of a rare epithelioid malignancy

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.

Melanoma with Prominent Pigment Synthesis (Animal-Type Melanoma)

Melanoma with prominent pigment synthesis or animal-type melanoma (ATM) is a very rare type of melanoma. Its histogenesis has not been elucidated and ultrastructural features have not been described in human beings. We present an additional case of ATM in a 28-year-old woman with positive sentinel node biopsy and provide the results of electron microscopic studies. Histopathologically, the skin lesion was composed of heavily pigmented neoplastic cells mostly arranged as large sheets, focally also in a nodular growth pattern. After bleaching, the neoplastic cells demonstrated round nuclei with 1 or rarely 2 conspicuous nucleoli and a prominent nuclear membrane and abundant, gray, slate-like cytoplasm. Some cells demonstrated round cytoplasmic inclusions. There was no nuclear pleomorphism, and only a few mitotic figures could be found after extensive search. Multiple areas of necrosis en masse of tumor cells were seen. The lymph node biopsy revealed a complete effacement of the lymph node architecture by the extensive proliferation of hyperpigmented cells in the parenchyma. Immunohistochemically, the same pattern of staining was seen on the bleached and unbleached slides both in the skin and in the lymph node. The neoplastic cells stained positively with MiTF (nuclei), NSE, NKI/C3, tyrosinase (weak), p53, and CD68. S-100 protein, HMB45, Melan A, Mac367, and lysozyme reacted negatively. Occasional cells (<1%) reacted with MIB-1. Ultra-structural studies revealed that the neoplastic cells possessed a large, indented nucleus with a prominent nuclear membrane, a single (para) centrally located nucleolus, and peripherally marginated chromatin. The cytoplasm was abundant and contained numerous single melanosomes and rare compound melanosomes. The melanosomes were in stages II to IV of maturation, with a marked predominance of stage II and stage III melanosomes. There was a high number of aberrant melanosomes with a wide variety of configurations. Melanophages were a minor component of the lesion. Our ultrastructural studies provide unequivocal evidence that ATM is a neoplasm of melanosome-producing cells. We also review the literature on ATM.

Gene expression patterns and gene copy number changes in dermatofibrosarcoma protuberans

Dermatofibrosarcoma protuberans (DFSP) is an aggressive spindle cell neoplasm. It is associated with the chromosomal translocation, t(17:22), which fuses the COL1A1 and PDGFbeta genes. We determined the characteristic gene expression profile of DFSP and characterized DNA copy number changes in DFSP by array-based comparative genomic hybridization (array CGH). Fresh frozen and formalin-fixed, paraffin-embedded samples of DFSP were analyzed by array CGH (four cases) and DNA microarray analysis of global gene expression (nine cases). The nine DFSPs were readily distinguished from 27 other diverse soft tissue tumors based on their gene expression patterns. Genes characteristically expressed in the DFSPs included PDGF beta and its receptor, PDGFRB, APOD, MEOX1, PLA2R, and PRKCA. Array CGH of DNA extracted either from frozen tumor samples or from paraffin blocks yielded equivalent results. Large areas of chromosomes 17q and 22q, bounded by COL1A1 and PDGF beta, respectively, were amplified in DFSP. Expression of genes in the amplified regions was significantly elevated. Our data shows that: 1) DFSP has a distinctive gene expression profile; 2) array CGH can be applied successfully to frozen or formalin-fixed, paraffin-embedded tumor samples; 3) a characteristic amplification of sequences from chromosomes 17q and 22q, demarcated by the COL1A1 and PDGF beta genes, respectively, was associated with elevated expression of the amplified genes.

Expression of the histiocytic marker PG-M1 in granuloma annulare and rheumatoid nodules of the skin

BACKGROUND

The expression of PG-M1, the most specific histiocytic marker, has not yet been studied in granuloma annulare (GA) and other palisaded granulomas of the skin. We evaluated the reactivity of PG-M1 with a series of GA and rheumatoid nodules (RN) to establish the sensitivity and potential usefulness of this marker in the diagnosis and characterization of these entities.

METHODS

Histological sections from 30 GA and 15 RN were immunostained with PG-M1. For comparison, additional sections were stained with KP-1 and lysozyme. The stains were recorded as negative, weakly positive (1+) and strongly positive (2+).

RESULTS

PG-M1 stained all cases of GA (100%). KP-1 and lysozyme stained 26 (86%) and 18 (60%) GA cases, respectively. PG-M1 exhibited a significantly stronger staining intensity (1.8 +/- 0.07) when compared with KP-1 (1.4 +/- 0.13) (p = 0.018) and with lysozyme (0.9 +/- 0.15) (p < 0.0001). All RN were stained by PG-M1 (100%). KP-1 and lysozyme stained 14 (93%) and six (40%) RN cases, respectively. PG-M1 staining intensity (1.6 +/- 0.13) was slightly higher than that of KP-1 (1.4 +/- 0.18) (p = 0.27) and significantly higher than that of lysozyme (0.4 +/- 0.13) (p < 0.0001).

CONCLUSIONS

PG-M1 is consistently and strongly expressed by the histiocytic population of GA and RN, being more sensitive and reliable than other histiocytic markers. We recommend its use in difficult cases in which the histiocytic nature of the lesion needs to be confirmed.

The CD68 protein as a potential target for leukaemia-reactive CTL

CD68, a haematopoietic differentiation marker of the monocyte-macrophage lineage, is expressed in various human malignancies including chronic and acute myeloid leukaemia (AML). While the majority of normal CD34(+) cells are negative for CD68 expression, CD34(+) cells from AML patients produce elevated amounts of this protein. The purpose of this study was to identify CTL epitopes in the human CD68 protein. Mouse CD68 was also analysed to search for epitopes that could be used in murine tumor model. Peptides binding to murine H2(b) class I molecules were identified and used to stimulate CTL responses from allogeneic donor mice to avoid immunological tolerance. High avidity CTL clones specific for three different peptide epitopes did not kill CD68-expressing murine target cells, indicating that endogenous antigen processing failed to produce sufficient amounts of these peptides. In contrast, allo-restricted human CTL specific for an HLA-A2-binding peptide of CD68 recognised not only picomolar concentrations of peptide, but also displayed low levels of killing against HLA-A2-positive K562 and THP-1 leukemia cell lines and blast cells from AML patients. These data suggest that human leukaemia cells express limited amounts of CD68-derived peptides, and that high avidity CTL capable of recognising sub-picomolar concentrations of peptides are required for efficient killing of leukaemia cells.

The histiocytic marker PG-M1 is helpful in differentiating histiocytes and histiocytic tumors from melanomas

Previous studies have shown that immunohistochemical stains for histiocytes are immunoreactive for melanomas. Accordingly, their value in differentiating histiocytes and histiocytic lesions from melanomas was questioned. PG-M1, the most specific histiocytic marker, was not evaluated in these studies. Our aims were to assess the reactivity of PG-M1 with a series of primary cutaneous and metastatic melanomas and to establish the potential usefulness of this antibody in the differentiation between histiocytes and histiocytic tumors and melanomas. PG-M1 staining was performed in 50 primary cutaneous and metastatic melanomas. For comparison, additional sections were stained with KP-1 and lysozyme (commonly used as histiocytic markers) and with S-100 and HMB-45 (commonly used as melanoma markers). The intensity (1+, 2+) and extent (1+ to 4+) were recorded semiquantitatively. PG-M1 stained weakly (1+) and focally (2+) only four cases of melanoma (8%). In contrast, histiocytes were strongly reactive for PG-M1 in all cases, being readily differentiated from melanoma cells including the positive cases. KP-1 stained melanoma cells in 44 cases (88%), lysozyme in 11 cases (22%), S-100 in 50 cases (100%), and HMB-45 in 48 cases (96%). No changes were found after restaining of selected KP-1 and lysozyme positive melanomas using an endogenous avidin/biotin blocking kit. PG-M1 is helpful in discriminating histiocytes and histiocytic lesions from melanoma cells. We recommend its inclusion in any antibody panel put together to distinguish between them.

Clear cell atypical fibroxanthoma:a clinicopathologic study

INTRODUCTION

The atypical fibroxanthoma (AFX) is considered by most authorities to represent a superficial or minimally invasive variant of malignant fibrous histiocytoma that most often presents as a solitary nodule on the sun-exposed skin of the elderly. Among the rarest variants is the clear cell AFX, a lesion which raises consideration to a differential diagnosis encompassing a variety of neoplastic and non-neoplastic clear cell proliferations.

METHODS

We describe three cases of a distinctive cutaneous neoplasm arising in the sun-exposed skin of elderly patients. In all cases, formalin-fixed, paraffin-embedded tissue was available for analysis. The histology in concert with the immunophenotype was held to be diagnostic of the clear cell variant of AFX.

RESULTS

All tumors comprised sheets of large cells with foamy cytoplasms and hyperchromatic, polyploid nuclei manifesting frequent and atypical mitoses. The critical cells in our cases expressed CD68 but none of CD3, CD20, CD34, S-100 protein, muscle-specific actin, factor XIIIa, Melan-A, carcinoembryonic antigen, or cytokeratin.

CONCLUSION

Although typical examples of AFX provoke diagnostic consideration of spindle cell cancers of the skin (most often spindle cell melanoma, spindle cell squamous cell carcinoma, and leiomyosarcoma), the clear cell variant raises other differential diagnostic considerations instead. These include balloon cell melanoma, sebaceous carcinoma, pleomorphic liposarcoma, chordoma, parachordoma, tricholemmal carcinoma and clear cell squamous cell carcinoma. A diagnosis of AFX is one of exclusion; one must employ immunohistochemical markers to rule out the aforementioned differential diagnostic considerations. By reporting the fifth, sixth and seventh cases of clear cell AFX, we hope to alert dermatopathologists to this distinctive and unusual neoplasm, recognition of which is essential to avoid under- or over-diagnosis and inappropriate therapy.

Immunohistochemical distinction of epithelioid histiocytic proliferations from epithelioid melanocytic nevi

Histiocytic tumors can be confused with melanocytic nevi and malignant melanoma and vice versa. To explore the use of immunohistochemistry for this diagnostic problem, we examined the expression of S-100 protein, gp100 (the antigen recognized by HMB-45), tyrosinase (T311), Melan-A (A103), Factor XIIIa (FXIIIa), and CD68 in 10 juvenile xanthogranulomas (JXGs), five epithelioid histiocytomas (EHs), and 15 melanocytic nevi composed of large epithelioid cells. All epithelioid melanocytic nevi were immunoreactive for Melan-A, tyrosinase, and S-100 protein in most melanocytes. Four nevi were completely negative with HMB-45. Nine nevi had only a minor HMB-45-positive component in the superficial dermis. Two nevi were diffusely HMB-45-positive. Melanocytes in all nevi were completely negative for FXIIIa. Thirteen nevi were completely negative for CD68. Two nevi contained rare cells with weak staining for CD68. All 15 histiocytic proliferations were completely negative for Melan-A, tyrosinase, and gp100. They lacked expression of S-100 protein or had at most 10% immunopositive cells. In JXGs, most cells were strongly reactive for CD68, although only a few were positive for FXIIIa. In EHs, 40% to 60% of cells were immunoreactive for FXIIIa, and only 20% to 30% were positive for CD68. Our results demonstrate that Melan-A and tyrosinase are sensitive and specific markers to distinguish epithelioid melanocytic nevi from epithelioid histiocytic tumors.

Xanthogranulomas with inconspicuous foam cells and giant cells mimicking malignant melanoma: a clinical, histologic, and immunohistochemical study of three cases

Histiocytic proliferations can mimic melanocytic tumors and vice versa. The authors describe the clinical, histologic, and immunohistochemical findings of three predominantly mononuclear xanthogranulomas that were misdiagnosed as malignant melanoma by experienced pathologists. All lesions occurred in male patients ranging in age from 14 to 75 years. The tumors presented as dermal nodules, two of which were surrounded by an epidermal collarette and were ulcerated focally. The tumors were composed of a mixed population of large epithelioid and plump spindle cells with pink or pale cytoplasm arranged in nests and short fascicles. Occasional mononuclear cells had cytoplasmic vacuolar changes, but none had well-developed foamy cytoplasm. Rare, multinucleated giant cells were present, but they were not of the Touton type. Mitotic figures were found in all lesions. Immunohistochemically, most tumor cells (80%-90%) were strongly positive for CD68 and a minority of cells (10%-15%), located typically at the periphery of the tumor, was positive for factor XIIIa. Two tumors contained rare cells positive for S-100 protein (5% of tumor cells or less). All tumors were completely negative for tyrosinase (T311), gp100 (HMB-45), and Melan-A (A103). Giant and foam cell-poor variants of juvenile xanthogranuloma have been reported previously, mainly in young children. Their occurrence in adolescents and adults is underrecognized. Knowledge of this variant is important to avoid misdiagnosing a benign tumor as malignant melanoma.

Morphological and immunophenotypic variations in malignant melanoma

A variety of cytomorphological features, architectural patterns and stromal changes may be observed in malignant melanomas. Hence, melanomas may mimic carcinomas, sarcomas, benign stromal tumours, lymphomas, plasmacytomas and germ cell tumours. Melanomas may be composed of large pleomorphic cells, small cells, spindle cells and may contain clear, signet-ring, pseudolipoblastic, rhabdoid, plasmacytoid or balloon cells. Various inclusions and phagocytosed material may be present in their cytoplasm. Nuclei may show bi- or multi-nucleation, lobation, inclusions, grooving and angulation. Architectural variations include fasciculation, whorling, nesting, trabeculation, pseudoglandular/pseudopapillary/pseudofollicular, pseudorosetting and angiocentric patterns. Myxoid or desmoplastic changes and very rarely pseudoangiosarcomatous change, granulomatous inflammation or osteoclastic giant cell response may be seen in the stroma. The stromal blood vessels may exhibit a haemangiopericytomatous pattern, proliferation of glomeruloid blood vessels and perivascular hyalinization. Occasionally, differentiation to nonmelanocytic structures (Schwannian, fibro-/myofibroblastic, osteocartilaginous, smooth muscle, rhabdomyoblastic, ganglionic and ganglioneuroblastic) may be observed. Typically melanomas are S100 protein, NKIC3, HMB-45, Melan-A and tyrosinase positive but some melanomas may exhibit an aberrant immunophenotype and may express cytokeratins, desmin, smooth muscle actin, KP1 (CD68), CEA, EMA and VS38. Very rarely, neurofilament protein and GFAP positivity may be seen.

True histiocytic lymphoma of the esophagus in an HIV-positive patient: an ultrastructural study

A 56-year-old white woman, seropositive for human immunodeficiency virus for 18 months without signs of acquired immunodeficiency syndrome, presented with retrosternal pain and progressive dysphagia secondary to an exophytic esophageal mass. Biopsies of the tumor showed a malignant neoplasm composed of pleomorphic, noncohesive cells growing in a diffuse, sheet-like fashion. Immunohistochemically, tumor cells were nonreactive with epithelial, lymphoid, neural, and monocyte/macrophage markers. Despite the noncontributory immunohistochemical findings, ultrastructural study of the tumor cells revealed convincing histiocytic features. Individual cells possessed long, slender filopodial projections, prominent Golgi apparatus, residual bodies, rare lysosomes, and prelysosomes. Immunoglobulin heavy chain and T-cell receptor gamma gene rearrangement studies detected no evidence of a clonal gene rearrangement. The patient responded poorly to chemotherapy and died 5 months after her initial symptom of dysphagia.

Immunocytochemical analysis of MNDA in tissue sections and sorted normal bone marrow cells documents expression only in maturing normal and neoplastic myelomonocytic cells and a subset of normal and neoplastic B lymphocytes

The human myeloid cell nuclear differentiation antigen (MNDA) is a nuclear antigen known to be expressed in mature myelomonocytic cell lines. An extensive immunocytochemical evaluation of fixed tissues confirmed MNDA expression in normal maturing granulocytes and monocytes and in acute nonlymphocytic leukemias and chronic myelogenous leukemia. MNDA was not detected in normal tissue histiocytes but was found in activated macrophages and foreign body giant cells associated with inflammation. Flow cytometric cell sorting of normal bone marrow established that MNDA is initially expressed in myeloid blast cells. Examination of lymphoid tissues showed a low level of expression in a population of normal mande B lymphocytes but not in germinal center cells or plasma cells. A subset of B cell neoplasms expressing MNDA included hairy cell leukemia, parafollicular (monocytoid) B cell lymphoma, mantle cell lymphoma, and small lymphocytic lymphoma. Cell sorting of normal bone marrow showed MNDA expression in CD20+/CD10-/CD5- B cells. MNDA was not detected in other normal bone marrow or all other nonhematopoietic cells. The hematopoietic cell-specific pattern of MNDA expression was elucidated through a comprehensive analysis of normal and neoplastic tissues, and the results provide further evidence of the coexpression of B- and myeloid cell markers in neoplastic B cells and identify a normal B cell population that might be related to the cell of origin of a subset of B cell neoplasms.

Immunohistochemical and clonal analysis of minute pulmonary meningothelial-like nodules

The histogenesis of meningothelial-like nodule or so-called minute pulmonary chemodectoma remains unclear, with various immunohistochemical analyses giving inconsistent results. We performed an immunohistochemical and clonal analysis of minute pulmonary meningothelial-like nodules. Thirty-one histologically defined meningothelial-like nodules in 14 cases were stained immunohistochemically. One case had multiple lesions with brown pigment granules, which were positively stained with Berlin blue method, indicating the presence of hemosiderin. All meningothelial-like nodules were positive for vimentin and epithelial membrane antigen (EMA), but not for S-100 protein, chromogranin A, or synaptophysin. Five of 13 cases (13 of 28 lesions) were positive for CD68 by KP-1. Ten cases (24 lesions) stained for CD68 by PG-M1 were weakly positive. All lesions were negative for lysozyme, myosin, actin, keratin, and melanoma-associated antigen. Alveolar macrophages were intensely positive for CD68 and lysozyme in all examined cases. We analyzed the clonality of 11 minute pulmonary meningothelial-like nodule lesions in two female cases based on an X-chromosome-linked polymorphic marker, the human androgen receptor gene (HUMARA). The HUMARA was found to be amplified with or without prior digestion by the methylation-sensitive restriction endonuclease HpaII. Six of 11 lesions showed monoclonal expansion. Five lesions in a multiple case showed different patterns of monoclonality. Our findings showed that minute pulmonary meningothelial-like nodules have meningothelial-like and phagocytic characteristics but no muscular phenotype. Furthermore, some minute pulmonary meningothelial-like nodules may show monoclonal expansion, whereas others are polyclonal. Our data indicate that minute pulmonary meningothelial-like nodules are reactive rather than neoplastic.

Diagnosis: atypical fibroxanthoma or not? Evaluating spindle cell malignancies on sun damaged skin: a practical approach

Poorly differentiated spindle cell malignancies on sun damaged skin frequently pose a diagnostic challenge for dermatopathologists. The vast majority of these neoplasms ultimately are diagnosed as either atypical fibroxanthoma (AFX), spindle cell squamous cell carcinoma (SCSCC), or spindle cell melanoma (SCM), and rarely leiomyosarcoma or angiosarcoma. Light microscopic clues may suggest one of these neoplasms, but subtle and overlapping characteristics often render precise diagnosis impossible based on morphological features alone. Immunohistochemistry therefore is necessary to firmly and accurately diagnose the majority of spindle cell malignancies on sun damaged skin. We summarize typical clinical and histological findings associated with this group of malignancies and offer a practical immunohistochemical approach to use in their diagnosis.

K-ras oncogene mutations in osteoclast-like giant cell tumors of the pancreas and liver: genetic evidence to support origin from the duct epithelium

Osteoclast-like giant cell tumors (OCGTs) of the pancreas and liver are enigmatic tumors. Despite their striking morphologic resemblance to certain mesenchymal tumors of bone and tendon sheath, it has been suggested that these tumors may, in fact, arise from epithelial precursors. It is also unclear whether the osteoclast-like giant cells in OCGTs are neoplastic or nonneoplastic. We identified OCGTs of the pancreas and liver that were associated with atypical intraductal epithelial proliferations or mucinous cystic neoplasms. To determine the relationship between the noninvasive epithelial proliferations and the infiltrating OCGTs, each individual component was analyzed for mutations at codon 12 of the K-ras oncogene. Four of the five-duct epithelial lesions harbored activating mutations of the K-ras oncogene. In each case, the same K-ras mutation was also present in the mononuclear cells from the paired OCGT. Moreover, these same mutations were detected when the osteoclast-like giant cells were individually microdissected and analyzed. A panel of immunohistochemical stains was performed, and the osteoclast-like giant cells demonstrated macrophage differentiation. These cells were consistently reactive for the monocyte/macrophage marker KP1, but showed absent staining for a panel of epithelial markers. The infiltrating mononuclear cells lacked strong staining for epithelial markers and monocyte/macrophage markers. These findings suggest that OCGTs of the pancreas and liver are undifferentiated carcinomas that arise directly from intraductal epithelial precursors. The finding of K-ras mutations in the osteoclast-like giant cells may reflect their propensity to phagocytize tumor cells.

Podocytes undergo phenotypic changes and express macrophagic-associated markers in idiopathic collapsing glomerulopathy

Collapsing glomerulopathy (CG), a severe form of focal segmental glomerulosclerosis (FSG), is characterized by tuft retraction and consolidation in numerous glomeruli and changes in podocyte morphology and topography. Other glomeruli are less affected. Collapsing glomerulopathy is also characterized by tubulointerstitial atrophy and fibrosis. The pathophysiology of the glomerular and tubulointerstitial lesions is poorly understood. We studied renal tissue of five Black and three White patients, all human immuno-deficiency virus (HIV) negative, with nephrotic syndrome, renal failure, and histological evidence of CG. Immunohistochemistry identified normal podocyte phenotypes by podocalyxin, vimentin and complement receptor 1 (CR1) labeling. Three monoclonal antibodies were used to further characterize podocyte epitopes: anti-CD68 clone KP1, anti-CD68 clone PG-M1 and anti-M130 clone M18 (Ber-MAC3). Light microscopy of collapsed glomeruli showed podocyte swelling, vacuolization, multinucleation, "cobblestone-like" alignment around the glomerular tuft, and pseudo-crescent formation in Bowman's space. In collapsed glomeruli, podocalyxin, vimentin and CR1 labeling tagged both normal and vacuolated podocytes still attached to the GBM, but labeling was not found in cobblestone-like podocytes or in podocytes detached from the GBM. Conversely, numerous podocytes undergoing detachment and shedding into Bowman's space expressed macrophagic-associated epitopes. Cells with macrophagic-associated epitopes clumped in cystically dilated tubules and were aligned in tubules of smaller caliber. Their appearance was that of viable cells. There was no morphologic indication that these cells expressing macrophage-associated antigens originated from outside the glomeruli or outside the tubules. We conclude that in CG podocytes detach from the GBM, lose their normal podocytic phenotype and acquire macrophage differentiation antigens. The presence of cells with such antigens in tubular lumens suggests that detached metaplastic podocytes progress along the tubule or, alternatively, that CG tubular cells also undergo metaplastic changes into macrophage-like cells.

Comparative immunoreactivity of CD-68 and HMB-45 in malignant melanoma, neural tumors and nevi

The monoclonal antibody CD 68 (KP 1) reacts with fibrohistiocytic and some epithelial neoplasms; its reactivity compared with that of HMB 45 in malignant melanoma (MM) and neural tumors needs further elucidation. Using a streptavidin-biotin-immunoperoxidase procedure, we examined the reactivity of 65 MM (46 conventional, 1 polypoid, 6 desmoplastic [DMM], and 12 metastatic), 21 neurofibromas, 1 neurofibrosarcoma, 10 schwannomas, 1 perineurioma, 2 neurothekeomas, and 14 blue and 26 other nevi for CD-68, HMB-45-defined antigen, S 100 and neurofilament protein. A positive staining for CD 68 was observed in 38 of 42 primary, 5 of 6 DMM, and 11 of 12 metastatic melanomas; 6 of 10 schwannomas; 5 of 10 nevi with junctional component and all 14 blue nevi. All 21 neurofibromas, 1 each neurofibrosarcoma and perineurioma, both neurothekeomas, and all 12 nevi with dermal component were CD 68-negative. HBM 45 was expressed by all 44 primary, none of 6 DMM, and 7 of 12 metastatic melanomas; by none of 10 schwannomas, 6 neurofibromas, 1 neurofibrosarcoma, 1 perineurioma and 2 neurothekeomas. Both junctional nevi, 8 of 10 nevi with junctional components, 1 of 10 dermal components of junctional nevi, and 11 of 13 blue nevi were also HMB 45 positive. Except for 1 perineurioma, S 100 decorated all tumors examined. NF was immunoreactive in 1 of 45 conventional melanomas, 2 of 21 neurofibromas, 2 of 10 schwannomas, and 3 of 10 blue nevi; it was non-reactive in all polypoid, desmoplastic and metastatic melanomas; neurofibrosarcoma, perineurioma, neurothekeoma and other nevi. We conclude that the CD-68-reactivity in primary melanomas, neurofibromas, neurofibrosarcomas, perineuriomas, and nevi was similar to that of HMB 45. The significantly higher CD 68-positivity than of HMB 45 in metastatic and desmoplastic melanomas and schwannomas may be of diagnostic value.

Atypical fibroxanthoma. An unusual variant with osteoclast-like giant cells

We report three cases of an unusual variant of atypical fibroxanthoma with numerous multinucleated osteoclast-like giant cells. Histologically, the lesions were composed of uniformly dispersed multinucleated osteoclast-like giant cells within a pleomorphic cellular proliferation with microscopic and histochemical features of atypical fibroxanthoma. Multinucleated osteoclast-like giant cells, however, stained with KP-1, a macrophage-associated antigen only. These cells are not necessarily an integral part of the tumor and may represent a reactive histiocytic component.

Reticulohistiocytoma involving the skin, subcutaneous tissue and a regional lymph node

A 30-year-old female complained of a surface-eroded solitary nodule on the right thigh. Histologically, the dermal lesion consisted of uniform-sized polygonal cells with eosinophilic, 'ground glass' cytoplasm. Mitoses were infrequent. Under the histopathologic diagnosis of amelanotic melanoma, wide resection of the skin and dissection of the inguinal lymph nodes were performed. The subcutaneous tissue and a lymph node showed nodular proliferation of histiocytoid cells, in association with hemosiderin-laden multinucleated giant cells. The mononuclear cells were immunoreactive for factor XIIIa, while the multinucleated cells were positive for CD68, lysozyme and HLA-DR. In the lymph node tissue, a considerable number of mononuclear cells positive for CD68 were noted. CD34, alpha-smooth muscle actin, desmin and HMB45 were negative. Ultrastructurally, the mononuclear cells were rich in 100 nm vesicles and 180-350 nm lysosome-like granules. Interdigitation of the plasma membranes was seen in the multinucleated cells. The patient did not complain of joint symptoms, and has been disease-free for 5 years. The histologic and immunohistochemical features are consistent with so-called 'reticulohistiocytoma', though the site of histiocytic growth was unusual.