CD117, CK20, TTF-1, and DNA topoisomerase II-alpha antigen expression in small cell tumors

ATOH1, TFAP2B, and CEACAM6 as Immunohistochemical Markers to Distinguish Merkel Cell Carcinoma and Small Cell Lung Cancer

Merkel cell carcinoma (MCC) and small cell lung cancer (SCLC) can be histologically similar. Immunohistochemistry (IHC) for cytokeratin 20 (CK20) and thyroid transcription factor 1 (TTF-1) are commonly used to differentiate MCC from SCLC; however, these markers have limited sensitivity and specificity. To identify new diagnostic markers, we performed differential gene expression analysis on transcriptome data from MCC and SCLC tumors. Candidate markers included atonal BHLH transcription factor 1 (ATOH1) and transcription factor AP-2β (TFAP2B) for MCC, as well as carcinoembryonic antigen cell adhesion molecule 6 (CEACAM6) for SCLC. Immunostaining for CK20, TTF-1, and new candidate markers was performed on 43 MCC and 59 SCLC samples. All three MCC markers were sensitive and specific, with CK20 and ATOH1 staining 43/43 (100%) MCC and 0/59 (0%) SCLC cases and TFAP2B staining 40/43 (93%) MCC and 0/59 (0%) SCLC cases. TTF-1 stained 47/59 (80%) SCLC and 1/43 (2%) MCC cases. CEACAM6 stained 49/59 (83%) SCLC and 0/43 (0%) MCC cases. Combining CEACAM6 and TTF-1 increased SCLC detection sensitivity to 93% and specificity to 98%. These data suggest that ATOH1, TFAP2B, and CEACAM6 should be explored as markers to differentiate MCC and SCLC.

Comparison of the Basal Cell Carcinoma (BCC) Tumour Microenvironment to Other Solid Malignancies

Basal cell carcinoma (BCC) is the most common form of skin cancer, contributing to nearly a third of new cancer cases in Western countries. Most BCCs are considered low risk "routine" lesions that can either be excised through surgery or treated with chemotherapeutic agents. However, around 1-2% of BCC cases are locally aggressive, present a high risk of metastasis, and often develop chemoresistance, termed advanced BCC. There currently exists no animal model or cell line that can recapitulate advanced BCC, let alone intermediate-risk and high-risk early BCC. We previously found that aggressive BCC tumours presented a Th2 cytokine inflammation profile, mesenchymal stem cell properties, and macrophage-induced tumoral inflammation. In this study, we aimed to identify potential BCC "relatives" among solid-organ malignancies who present similar immune cell proportions in their microenvironment compositions. Using immune cell type deconvolution by CIBERSORTx, and cell type enrichment by xCell, we determined three cancers with the most similar tumour microenvironments as compared to BCC. Specifically, chromophobe renal cell carcinoma, sarcoma, and skin cutaneous melanoma presented significance in multiple cell types, namely in CD4+ T lymphocytes, gammadelta T lymphocytes, and NK cell populations. Consequently, further literature analysis was conducted to understand similarities between BCC and its "relatives", as well as investigating novel treatment targets. By identifying cancers most like BCC, we hope to propose prospective druggable pathways, as well as to gain insight on developing a reliable animal or cell line model to represent advanced BCC.

Mixed adenoneuroendocrine carcinomas of stomach and ampulla of vater after curative-intent resection: a single center cases series

Background

Mixed adenoneuroendocrine carcinoma is a rare clinical manifestation, especially in the gastric and ampullary. The purpose of this study was to investigate the clinicopathological features and prognosis of mixed adenoneuroendocrine carcinoma in the gastric and ampullary and summarize related treatment suggestions.

Methods

In all, 32 cases of mixed adenoneuroendocrine carcinoma in the gastric and ampullary that were diagnosed from resected specimens were analyzed from 2009 to 2015. The corresponding demographic, clinicopathological and survival data were retrospectively reviewed.

Results

The 1-year, 3-year and 5-year survival rates were 78.1%, 28.1 and 9.4%, respectively, and the median overall survival was 28.0 months. In all, 75.0% (24/32) had lymph node metastasis at the time of initial diagnosis. A multivariate analysis revealed that TNM stage (HR 6.444 95%CI 1.477–28.121 P = 0.013), lymph nodes metastasis (HR10.617 95%CI 1.409–79.997 P = 0.022), vascular invasion (HR 5.855 95%CI 1.719–19.940 P = 0.005), grade of the adenocarcinoma component (HR 3.876 95%CI 1.451–10.357 P = 0.007) and CD56 positivity (HR 0.265 95%CI 0.100–0.705 P = 0.008) were independent predictors of overall survival.

Conclusions

Mixed adenoneuroendocrine carcinoma is an aggressive clinical entity with a poor prognosis. Taking both the neuroendocrine component and the adenocarcinoma component into consideration of optimal treatment is strongly recommended.

Clinicopathologic features of cutaneous metastases from internal malignancies

Background

Cutaneous metastasis (CM) is the spread of cancer cells from a primary site to the skin and is rarely the first sign of silent cancer. We investigated the clinicopathological characteristics of CM from internal malignancies in Korean patients treated at our institution over 20 years.

Methods

The clinicopathological findings of 112 patients (62 females, 50 males) with CM diagnosed at Yeungnam University Hospital between 2000 and 2020 were retrospectively reviewed.

Results

Mean patient age was 58.6 years (range, 26 to 87 years), and the most common primary cancer site was breast (74.2%) in women and lung (36.0%) in men. Ninety-six patients (85.7%) presented with CM after primary tumor diagnosis. CM from the lung or biliary tract usually occurred within 2 years of primary tumor diagnosis, whereas metastases from the breast and kidney occurred several years later. The chest, abdomen, and scalp were common sites of CM. Breast cancer usually metastasized to chest skin, while gastrointestinal tract cancers commonly metastasized to the abdomen. The scalp was a common location for CM from various tumors. The most common dermatologic presentations were nodules and masses. Immunohistochemical studies helped identify underlying malignancies when primary tumors were unknown.

Conclusions

The relative frequency of CM parallels the overall incidence of primary malignant tumors, and CMs usually occur at anatomic sites close to the primary tumor. CM can be diagnosed based on clinical, radiological, and histological features; however, immunohistochemical study is required in some cases.

Danger is only skin deep: aggressive epidermal carcinomas. An overview of the diagnosis, demographics, molecular-genetics, staging, prognostic biomarkers, and therapeutic advances in Merkel cell carcinoma

Merkel cell carcinoma (MCC) is a high grade primary cutaneous neuroendocrine carcinoma and is among the most aggressive cutaneous malignancies. The rising incidence of MCC, together with its often rapidly aggressive course, underscore a critical need to recognize the histopathologic and the immunohistochemical features that inform its accurate diagnosis. In the current review, we summarize the current state of knowledge regarding the accurate diagnosis of MCC and the exclusion of other entities in the differential diagnosis. We provide a comprehensive review of genomic studies that identified the molecular-genetic drivers of MCC as well as a summary of studies identifying prognostic biomarkers that can facilitate risk stratification. Importantly, Merkel cell polyomavirus (MCPyV) appears to be causative in most cases of MCC and represents both a diagnostic and prognostic marker. Finally, as staging of MCC has undergone critical refinements with the introduction of the 8th Edition of the American Joint Committee on Cancer staging system, we provide an update on MCC staging. In particular, the prognostic significance of the sentinel lymph node (SLN) in MCC necessitates a systematic approach to its evaluation and diagnosis to ensure accurate and consistent risk stratification for patients, and we therefore provide a comprehensive overview of SLN evaluation in MCC. Finally, the intimate relationship between MCC and the integrity of the host immune system has led to paradigm-shifting therapeutic advances with the successful application of immune checkpoint blockade to treat patients with advanced disease, and we therefore summarize those studies and the correlative studies in which predictive biomarkers have been identified.

Cutaneous Metastases: A Review and Diagnostic Approach to Tumors of Unknown Origin

CONTEXT.—

Cutaneous metastases from a distant malignancy are a diagnostic challenge for pathologists. Secondary involvement of the skin by a metastatic process portends a much worse clinical prognosis than any primary cutaneous malignant mimickers. Immunohistochemical staining methods continue to evolve and are of paramount importance in diagnosis.

OBJECTIVE.—

To review the clinical, histopathologic, and immunohistochemical staining patterns for commonly encountered entities and discuss potential pitfalls in diagnosis. A practical guide useful in approaching cutaneous metastases of unknown primary is outlined.

DATA SOURCES.—

An extensive search and review of literature in PubMed was performed, processed, and condensed.

CONCLUSIONS.—

Cutaneous metastases have broad histopathologic patterns. They are nearly always dermal based, with an overall foreign appearance. They can be single papules/nodules or multiple in number, mimicking an inflammatory or infectious process. Ultimately, immunohistochemistry remains an essential diagnostic tool, and clinical correlation is paramount in the workup of these entities.

Acral Metastasis of the Fingers: Report of 2 Cases

Cutaneous metastases appear in 0.6% to 10.4% of malignant tumors and account for 2% of all cutaneous tumors. Metastasis to the skin may arise from progression of a known primary tumor or provide the first sign of an unsuspected one. Acral metastases are particularly unusual. Most derive from bone tumors. Clinical signs vary and the lesions generally resemble infection or inflammation, leading to diagnostic delays. When metástasis involves the fingers, the primary tumor is usually lung carcinoma. In contrast, toe involvement usually derives from a tumor in the genitourinary tract. A pathologic diagnosis in these cases is necessary and will suggest the location of the primary tumor. We report 2 cases of metástasis to the fingers. One is the first report of acral metástasis of a myoepithelial carcinoma of the breast. The other concerns acral metástasis as the first sign of lung carcinoma.

Update on Merkel Cell Carcinoma

Merkel cell carcinoma (MCC) is an aggressive cutaneous neuroendocrine carcinoma. Incidence of MCC continues to rise, and risk factors include advanced age, pale skin, chronic sun exposure, and immune suppression. Diagnosing MCC utilizes a combination of morphology and immunohistochemistry. Merkel cell polyomavirus (MCPyV) is present in approximately 70-80% of MCCs and represents a key pathogenic driver in those MCCs. In contrast, MCPyV-negative MCCs arise through progressive accumulation of ultraviolet-light induced somatic mutations. Staging of MCC proceeds according to the American Joint Commission on Cancer (AJCC) 8th Edition, which utilizes features of the primary tumor together with regional lymph node(s) (clinically and/or pathologically detected) and/or distant metastases. Many potentially useful biomarkers have been studied to refine risk stratification in MCC. In recent years, the host immune infiltrate has been leveraged as immune checkpoint blockade has emerged as an efficacious mode of treatment for patients with advanced MCC.

Lymph Node Metastases of Merkel Cell Carcinoma from Unknown Primary Site: Report of Three Cases

Merkel cell carcinoma (MCC) is an uncommon aggressive neuroendocrine skin carcinoma. It usually affects sun-exposed skin of white elderly people. MCC is characterized by a high incidence of early locoregional relapse and distant metastases. Because of its rarity and the resulting lack of prospective randomized trials, data regarding the optimal treatment of MCC are limited. Despite aggressive multimodality treatment, the prognosis of patients bearing MCC is often poor. We report three cases of lymph node metastases of MCC with unknown primary sites. Two patients died 17 and 28 months after diagnosis due to brain and pancreatic metastases, respectively, without evidence of cutaneous disease. The third patient is alive and free of tumor at 16 months from the diagnosis. After an accurate diagnosis of lymph node metastases from MCC, the absence of a primary tumor at complete initial evaluation and during adequate follow-up can confirm this particular clinical scenario. The prognosis seems to be analogous to that of cases with similar disease stage (lymph node involvement) but a known primary site.

Histologic Mimics of Basal Cell Carcinoma

CONTEXT

- Basal cell carcinoma (BCC) is the most common human malignant neoplasm and is a frequently encountered diagnosis in dermatopathology. Although BCC may be locally destructive, it rarely metastasizes. Many diagnostic entities display morphologic and immunophenotypic overlap with BCC, including nonneoplastic processes, such as follicular induction over dermatofibroma; benign follicular tumors, such as trichoblastoma, trichoepithelioma, or basaloid follicular hamartoma; and malignant tumors, such as sebaceous carcinoma or Merkel cell carcinoma. Thus, misdiagnosis has significant potential to result in overtreatment or undertreatment.

OBJECTIVE

- To review key features distinguishing BCC from histologic mimics, including current evidence regarding immunohistochemical markers useful for that distinction.

DATA SOURCES

- Review of pertinent literature on BCC immunohistochemistry and differential diagnosis.

CONCLUSIONS

- In most cases, BCC can be reliably diagnosed by histopathologic features. Immunohistochemistry may provide useful ancillary data in certain cases. Awareness of potential mimics is critical to avoid misdiagnosis and resulting inappropriate management.

Merkel Cell Carcinoma

Merkel cell carcinoma (MCC) encompasses neuroendocrine carcinomas primary to skin and occurs most commonly in association with clonally integrated Merkel cell polyomavirus with related retinoblastoma protein sequestration or in association with UV radiation-induced alterations involving the TP53 gene and mutations, heterozygous deletion, and hypermethylation of the Retinoblastoma gene. Molecular genetic signatures may provide therapeutic guidance. Morphologic features, although patterned, are associated with predictable diagnostic pitfalls, usually resolvable by immunohistochemistry. Therapeutic options for MCC, traditionally limited to surgical intervention and later chemotherapy and radiation, are growing, given promising early results of immunotherapeutic regimens.

Topics in histopathology of sweat gland and sebaceous neoplasms

This article reviews several topics regarding sweat gland and sebaceous neoplasms. First, the clinicopathological characteristics of poroid neoplasms are summarized. It was recently reported that one-fourth of poroid neoplasms are composite tumors and one-fourth are apocrine type lesions. Recent progress in the immunohistochemical diagnosis of sweat gland neoplasms is also reviewed. CD117 can help to distinguish sweat gland or sebaceous tumors from other non-Merkel cell epithelial tumors of the skin. For immunohistochemical differential diagnosis between sweat gland carcinoma (SGC) other than primary cutanesous apocrine carcinoma and skin metastasis of breast carcinoma (SMBC), a panel of antibodies may be useful, including p63 (SGC⁺ , SMBC^- ), CK5/6 (SGC⁺ , SMBC^- ), podoplanin (SGC⁺ , SMBC^- ) and mammaglobin (SGC^- , SMBC⁺ ). Comparison of antibodies used for immunohistochemical diagnosis of sebaceous carcinoma (SC) suggests that adipophilin has the highest sensitivity and specificity. Some authors have found that immunostaining for survivin, androgen receptor and ZEB2/SIP1 has prognostic value for ocular SC, but not extraocular SC. In situ SC is rare, especially extraocular SC, but there have been several recent reports that actinic keratosis and Bowen's disease are the source of invasive SC. Finally, based on recent reports, classification of sebaceous neoplasms into three categories is proposed, which are sebaceoma (a benign neoplasm with well-defined architecture and no atypia), borderline sebaceous neoplasm (low-grade SC; an intermediate tumor with well-defined architecture and nuclear atypia) and SC (a malignant tumor with invasive growth and evident nuclear atypia).

Application of electron microscopic analysis and fluorescent in situ hybridization technique for the successful diagnosis of extraskeletal Ewing's sarcoma

The diagnosis of soft tissue tumors is often challenging. Immunohistochemical investigation, let alone routine histopathological investigation, may not allow definitive diagnosis in some cases. To overcome such difficulties, more advanced techniques need to be adopted. Herein, we report an extremely rare 56-year-old Japanese female case of extraskeletal Ewing's sarcoma (ES), successfully diagnosed by electron microscopy (EM) using formalin-fixed sections and fluorescence in situ hybridization (FISH). The patient had a 2-year history of a tumor growing on the leg. In routine histopathology, invasive proliferation of tumor cells was observed in the dermis. Tumor cells were round and uniform with large hyperchromatic nuclei, which were positively stained for CD56, VS38c, Ki-67, MIC2 and vimentin, but not for pan-keratin AE1 + AE3, cytokeratin 20, chromogranin A, synaptophysin and neuron-specific enolase. As these findings were not conclusive to make the final diagnosis, EM specimens were prepared from formalin-fixed sections and subjected to investigation. Cell surface projections and dense core granules were detected, suggestive of either Merkel cell carcinoma or extraskeletal ES. Subsequent FISH analysis identified reciprocal translocation of the ESWR1 gene, enabling the final diagnosis of extraskeletal ES. This study provides useful information enabling the diagnosis of this uncommon soft tissue tumor.

Assigning site of origin in metastatic neuroendocrine neoplasms: a clinically significant application of diagnostic immunohistochemistry

The neuroendocrine epithelial neoplasms (NENs) include well-differentiated neuroendocrine tumors (WDNETs) and poorly differentiated neuroendocrine carcinomas (PDNECs). Whereas PDNECs are highly lethal, with localized Merkel cell carcinoma somewhat of an exception, WDNETs exhibit a range of "indolent" biologic potentials-from benign to widely metastatic and eventually fatal. Within each of these 2 groups there is substantial morphologic overlap. In the metastatic setting, the site of origin of a WDNET has significant prognostic and therapeutic implications. In the skin, Merkel cell carcinoma must be distinguished from spread of a visceral PDNEC. This review intends to prove the thesis that determining the site of origin of a NEN is clinically vital and that diagnostic immunohistochemistry is well suited to the task. It will begin by reviewing current World Health Organization terminology for the NENs, as well as an embryologic and histologic pattern-based classification. It will present population-based data on the relative frequency and biology of WDNETs arising at various anatomic sites, including the frequency of metastases of unknown primary, and comment on limitations of contemporary imaging techniques, as a means of defining the scope of the problem. It will go on to discuss the therapeutic significance of site of origin. The heart of this review is a synthesis of data compiled from >100 manuscripts on the expression of individual markers in WDNETs and PDNECs, as regards site of origin. These include proteins that are considered "key markers" and others that are either useful "secondary markers," potentially very useful markers that need to be further vetted, or ones that are widely applied despite a lack of efficacy. It will conclude with my approach to the metastatic NEN of unknown origin.

Specific analysis of KIT and PDGFR-alpha expression and mutational status in Merkel cell carcinoma

BACKGROUND

The purpose of this study was to explore the immunohistochemical and mutational status of the tyrosine kinases KIT and platelet derived growth receptor-alpha (PDGFRA) in Merkel cell carcinoma (MCC). Specifically, we examined the mutated exons in gastrointestinal stromal cell tumors that may confer a treatment response to imatinib mesylate.

METHODS

We evaluated KIT and PDGFRA immunostaining in 23 examples of MCC utilizing laser capture microdissection to obtain pure samples of tumor genomic DNA from 18 of 23 examples of MCC. PCR amplification and sequencing of KIT exons 9, 11, 13 and 17, and PDGFRA exons 10, 12, 14 and 18 for mutations was performed.

RESULTS

Fifteen of 23 tumors (65%) demonstrated CD117 expression and 22 of 23 tumors (95%) demonstrated PDGFRA expression. A single heterozygous KIT exon 11 base change resulting in an E583K mutation was discovered in 12 of 18 (66%) examples of MCC. In addition, a single nucleotide polymorphism was detected in eight of 18 tumors (44%) in exon 18 of PDGFRA (codon 824; GTC > GTT).

CONCLUSIONS

We discovered a novel somatic KIT exon 11 E583K mutation in 66% of tumors. This mutation has been previously described in a human with piebaldism and appears to represent an inactivating mutation. Therefore, despite expression of CD117 and PDGFRA, the absence of activating mutations in these tyrosine kinases makes KIT and PDGFRA unlikely candidates of MCC oncogenesis.

Cutaneous metastases from internal malignancies: a clinicopathologic and immunohistochemical review

Skin metastases occur in 0.6%-10.4% of all patients with cancer and represent 2% of all skin tumors. Skin metastases from visceral malignancies are important for dermatologists and dermatopathologists because of their variable clinical appearance and presentation, frequent delay and failure in their diagnosis, relative proportion of different internal malignancies metastasizing to the skin, and impact on morbidity, prognosis, and treatment. Another factor to take into account is that cutaneous metastasis may be the first sign of clinically silent visceral cancer. The relative frequencies of metastatic skin disease tend to correlate with the frequency of the different types of primary cancer in each sex. Thus, women with skin metastases have the following distribution in decreasing order of frequency of primary malignancies: breast, ovary, oral cavity, lung, and large intestine. In men, the distribution is as follows: lung, large intestine, oral cavity, kidney, breast, esophagus, pancreas, stomach, and liver. A wide morphologic spectrum of clinical appearances has been described in cutaneous metastases. This variable clinical morphology included nodules, papules, plaques, tumors, and ulcers. From a histopathologic point of view, there are 4 main morphologic patterns of cutaneous metastases involving the dermis, namely, nodular, infiltrative, diffuse, and intravascular. Generally, cutaneous metastases herald a poor prognosis. The average survival time of patients with skin metastases is a few months. In this article, we review the clinicopathologic and immunohistochemical characteristics of cutaneous metastases from internal malignancies, classify the most common cutaneous metastases, and identify studies that may assist in diagnosing the origin of a cutaneous metastasis.

Colorectal poorly differentiated neuroendocrine carcinomas and mixed adenoneuroendocrine carcinomas: insights into the diagnostic immunophenotype, assessment of methylation profile, and search for prognostic markers

Colorectal poorly differentiated neuroendocrine carcinomas (NECs) and mixed adenoneuroendocrine carcinomas (MANECs) are well-recognized entities generally known to be associated with biological aggressiveness and poor patient survival. However, a few published papers have highlighted the existence of a subgroup of tumors with a better survival than expected; however, to date, there are no established parameters that usefully identify this category. In the present study we have investigated the morphologic features, the CpG methylator phenotype (CIMP), microsatellite instability (MSI), and the immunohistochemical profile, including the expression of transcription factors (TTF1, ASH1, CDX2, and PAX5), stem cell markers (CD117 and CD34), and cytokeratins 7 and 20, in a series of 39 carcinomas (27 NECs and 12 MANECs) to better characterize such neoplasms and to search for prognostic indicators. No different patient survival was observed between NECs and MANECs. Neoplasms showed a heterogenous spectrum of morphologic and immunohistochemical features; however, only large-cell subtype, significant peritumoral lymphoid reaction, CD117 immunoreactivity, vascular invasion, and MSI/CIMP+ status were significantly correlated with prognosis on univariable analysis. Furthermore, vascular invasion and CD117 immunoreactivity were independent prognostic markers on multivariable analysis. In addition to these prognostic features, neoplasms showed different expression of transcription factors, stem cell markers, and cytokeratins that should be considered for diagnostic purposes and, especially, for discriminating among possible differential diagnoses.

TTF1 expression in normal lung neuroendocrine cells and related tumors: immunohistochemical study comparing two different monoclonal antibodies

Thyroid transcription factor-1 (TTF1) regulates lung morphogenesis and differentiation, and its immunohistochemical expression is used for identifying lung neoplasms. The 8G7G3/1 antibody has been used in previous studies, but a different and more sensitive anti-TTF1 antibody, named SPT24, has become commercially available. Since the immunohistochemical expression of TTF1 in normal lung neuroendocrine (NE) cells has not been previously investigated and its utility in the diagnosis of lung NE tumors is a controversial issue, we studied the TTF1 expression in normal adult and fetal lungs, in 83 pulmonary NE neoplasms, in 131 non-lung NE tumors and in 36 metastases from these neoplasms using these two antibodies. A TTF1 immunoreactivity was demonstrated in normal fetal and adult NE cells when using the SPT24 clone. Conversely, using the 8G7G3/1 antibody, only rare fetal neuroendocrine cells were TTF1 positive while adult NE cells were negative. The SPT24 clone identified TTF1 expression in more carcinoids, most of them peripherally located, and poorly differentiated NE carcinomas than the 8G7G3/1 clone. Non-pulmonary well-differentiated NE tumors were negative for both antibodies. Among the 45 non-pulmonary poorly differentiated NE carcinomas 11% were positive for 8G7G3/1 and 18% for SPT24. TTF1 expression in metastases perfectly reflected that detected in the related primary tumors. Our results indicate that the SPT24 antibody is more sensitive than the 8G7G3/1 clone for labeling lung carcinoids and it appears particularly useful in detecting peripheral neoplasms. In addition, the expression of TTF1 in normal NE cells suggests a possible role for the transcription factor in their development and differentiation.

Merkel cell carcinoma: correlation of KIT expression with survival and evaluation of KIT gene mutational status

Merkel cell carcinoma is one of the most aggressive primary cutaneous malignancies. Because some Merkel cell carcinomas express the receptor tyrosine kinase KIT, we aimed to evaluate the correlation of KIT expression with the outcome and the presence of activating mutations in the KIT gene in Merkel cell carcinoma. A total of 49 tumors from 40 patients with a diagnosis of Merkel cell carcinoma were identified, of which 30 cases from 21 patients were used in the study. KIT expression was assessed by immunohistochemistry on formalin-fixed, paraffin-embedded material. Cases were divided into low expressors (0-1+ staining intensity) and high expressors (2-3+ staining intensity). Direct sequencing of exons 9, 11, 13, 17, and 18 of the KIT gene spanning the extracellular, juxtamembrane, and tyrosine kinase domains was performed for cases with high KIT expression. Thirty tumors from 21 patients were analyzed for KIT expression. High KIT expression was seen in 67% of the patients. Five-year survival rates in tumors expressing high versus low levels of KIT were 0% versus 57.8%, respectively; however, this dramatic difference did not reach statistical significance (P = .07). A total of 4 point mutations were identified in 18 tumors analyzed. Two of these were silent mutations involving exons 17 and 18, and 2 involved intron 16-17. Two of the identified mutations may represent novel polymorphisms. Our work suggests a correlation between KIT expression and a worse prognosis in Merkel cell carcinoma patients, raising the possibility of an active role of this receptor in tumor progression and metastasis. However, we did not identify KIT activating mutations in any of the tumors analyzed.

Skin metastasis: a pathologist's perspective

Skin metastasis is defined as the spread of malignant cells from a primary malignancy to the skin. It is one manifestation of systemic spread of cancer. The tumor cells originate either from an internal malignancy or from a primary skin cancer. This study presents a literature review concerning these issues as well as this author's experience encountered throughout 19 years of surgical pathology and dermatopathology practice. Several conclusions are evident. Generally, skin metastases are encountered in 0.7-9% of all patients with cancer and as such the skin is an uncommon site of metastatic disease when compared to other organs. There is usually a long-time lag between the diagnosis of the primary malignancy and the recognition of the skin metastases. However, these metastases may be the first indication of the clinically silent visceral malignancies. The regional distribution of the skin metastasis, although not always predictable, is related to the location of the primary malignancy and the mechanism of metastatic spread. The relative frequency of skin metastasis correlates with the type of primary cancer, which occurs in each sex. For instance, lung and breast carcinomas are the most common primaries that send skin metastasis in men and women, respectively. The head and neck region and the anterior chest are the areas of greatest predilection in men. The anterior chest wall and the abdomen are the most commonly involved sites in women. Skin metastases usually appear as non-specific groups of discrete firm painless nodules that emerge rapidly without any explanation. They vary in size from so tiny as to be of 'miliary lesions' to as large as 'Hen's egg size'. Some skin metastasis may mimic specific dermatological conditions such as cutaneous cyst, dermatofibroma, pyogenic granuloma, hemangioma, papular eruptions, herpes zoster eruptions, rapidly infiltrating plaques, alopecic patches, cellulitis and erysipelas. Histologically, the skin metastases usually show features reminiscent of the primary malignancy, but with variable degrees of differentiation. Molecularly, skin metastasis is an organized, non-random and organ-selective process orchestrated by interaction among several heterogeneous molecules, which are largely unknown. Metastasis to the skin is often a pre-terminal event that heralds poor outcome.

Merkel cell carcinoma: lack of KIT positivity and implications for the use of imatinib mesylate

The large variability (7% to 100%) in previously reported rates of receptor tyrosine kinase KIT expression in Merkel cell carcinoma (MCC) may be owing to the use of heat-induced epitope retrieval. High frequency of reported KIT reactivity by immunohistochemistry (IHC) in part prompted the initiation of a phase 2 clinical trial of imatinib mesylate (Gleevec, Novartis Pharmaceuticals, East Hanover, NJ) for the treatment of advanced MCC. Our experience has been that a small number of MCCs (12.5%) are positive for KIT by IHC. We also found a higher rate of apparently KIT-positive MCCs (75%) using heat-induced epitope retrieval. Our anecdotal experience with the use of imatinib mesylate has been disappointing. As IHC detection of KIT expression does not correlate with the presence of KIT-activating mutations, protein expression as tested by IHC should not be used to determine if patients would respond to imatinib mesylate. Indeed, our review of the literature and the apparent lack of efficacy of imatinib mesylate for MCC in a recent phase 2 trial suggest a minor role for KIT signaling in MCC tumorigenesis.

Transcription expression and clinical significance of TTF-1 mRNA in pleural effusion of patients with lung cancer

The aim of this study was to evaluate diagnostic utility of thyroid transcription factor 1 (TTF-1) mRNA in pleural effusions (PEs) of patients with lung cancer, especially primary pulmonary adenocarcinoma (PPA). Transcription levels of TTF-1 were detected by reverse transcription polymerase chain reaction (RT-PCR) in PEs of patients with lung cancer (56 cases) and with lung benign diseases (44 cases). The expression rate of TTF-1 mRNA was significantly higher in PEs of patients with lung cancer (73.2%) than with benign lung diseases (0%). In subclasses, the expression rate of TTF-1 mRNA was obviously higher in PEs of patients with PPA (93.0%) than with metastatic pulmonary adenocarcinoma (0%) and with primary pulmonary squamous cell carcinoma (12.5%). When compared with immunocytochemistry and cytology, TTF-1 mRNA gave the best diagnostic performance in diagnosing PPA: sensitivity of 93.0%, specificity of 100%, and accuracy of 96.6%, respectively. As a molecular marker of detecting pleural micrometastasis, TTF-1 mRNA may be helpful to diagnose the cancer cells in PEs of patients with lung cancer, especially with PPA.

Differential gene expression in primary human skin keratinocytes and fibroblasts in response to ionizing radiation

Although skin is usually exposed during human exposures to ionizing radiation, there have been no thorough examinations of the transcriptional response of skin fibroblasts and keratinocytes to radiation. The transcriptional response of quiescent primary fibroblasts and keratinocytes exposed to from 10 cGy to 5 Gy and collected 4 h after treatment was examined. RNA was isolated and examined by microarray analysis for changes in the levels of gene expression. Exposure to ionizing radiation altered the expression of 279 genes across both cell types. Changes in RNA expression could be arranged into three main categories: (1) changes in keratinocytes but not in fibroblasts, (2) changes in fibroblasts but not in keratinocytes, and (3) changes in both. All of these changes were primarily of p53 target genes. Similar radiation-induced changes were induced in immortalized fibroblasts or keratinocytes. In separate experiments, protein was collected and analyzed by Western blotting for expression of proteins observed in microarray experiments to be overexpressed at the mRNA level. Both Q-PCR and Western blot analysis experiments validated these transcription changes. Our results are consistent with changes in the expression of p53 target genes as indicating the magnitude of cell responses to ionizing radiation.

Metastatic Merkel cell carcinoma with positive expression of thyroid transcription factor-1--a case report

We report on a case of metastatic Merkel cell carcinoma in a 74-year-old patient with positive staining for thyroid transcription factor-1. This represents a new immunohistochemical staining pattern for Merkel cell carcinoma and has implications regarding the accurate diagnosis of this tumor type.

Merkel Cells, Normal and Neoplastic: An Update

Merkel cells (MC) occur in the basal epidermal layer, hair follicles, and oral mucosa, as complexes with sensory axons. The axons transduce slowly adapting type I mechanoreception, and MC modulate their sensitivity. MC also determine and maintain the 3-dimensional epidermal structure. They have neuroendocrine granules, rigid spinous processes, and desmosomal junctions with each other and with keratinocytes. Rare MC are dermaWl. Current evidence supports a basal cell origin. Merkel cell carcinomas (MCC) occur mostly in sun-exposed skin in old age. Trabecular, intermediate, or small cell in pattern, MCC have neuroendocrine granules, intercellular junctions, rigid spinous processes, and a paranuclear collection of intermediate filaments staining for cytokeratin 20. Most MCC behave indolently, but those with the small cell pattern, and some with the intermediate pattern, are aggressive and rapidly fatal.

Platelet-derived growth factor receptor alpha mutational status and immunohistochemical expression in Merkel cell carcinoma: implications for treatment with imatinib mesylate

BACKGROUND

It is not known if Merkel cell carcinomas (MCCs) show mutations in the platelet-derived growth factor receptor alpha (PDGFRA) gene similar to a subset of gastrointestinal stromal cell tumors. The purpose of this study was to analyze MCCs for mutations in the PDGFRA gene as well as to analyze those MCCs exhibiting a possible mutation in the PDGFRA gene for immunohistochemical expression of PDGFRA.

METHODS

We extracted tumor DNA from nine MCCs, performed polymerase chain reaction amplification of PDGFRA exons 10, 12, 14 and 18, and directly sequenced those gene products for mutations. In addition, we evaluated for PDGFRA immunostaining in three MCCs showing a possible PDGFRA gene mutation.

RESULTS

Three out of nine (33.3%) MCCs showed an identical novel single heterozygous base change in exon 10 of the PDGFRA gene leading to an amino acid substitution at codon 478. In addition, all three (100%) of those MCCs expressed PDGFRA.

CONCLUSIONS

Although it is unknown whether the base change described above represents a true mutation or a single nucleotide polymorphism, the fact that this change was absent in our control specimens suggests that this mutation may be oncogenic in nature and may make imatinib mesylate a possible therapeutic option in MCC.

Characterization of c-kit (CD117) expression in human normal pituitary cells and pituitary adenomas

c-kit (CD117) is a tyrosine kinase receptor involved in the proliferation, differentiation, and secretory functions of various cells. In experimental animal models, c-kit has been detected in the pars intermedia of the normal pituitary gland and in alpha-melanocyte-stimulating-hormone-positive adenomas and it has been suggested that it plays a role in regulating adrenocorticotropic hormone (ACTH) secretion. To the best of our knowledge, the expression of c-kit in normal human pituitary cells and in pituitary adenomas has never been reported, so the possible biological role of this receptor in the control of pituitary hormone secretion remains unclear. The aim of this study was to evaluate the immunohistochemical expression of c-kit in normal human pituitary glands and in a series of 62 well-characterized pituitary adenomas. In normal adenohypophyses, several cells, mainly located in the central mucoid wedge, showed a c-kit immunoreactivity (IR). Double label immunostaining procedures showed that the c-kit-IR cells corresponded to ACTH cells. Out of 62 adenomas, 15 (24%) were c-kit-IR, including 7/16 (44%) ACTH cell, 3/7 (42%) null cell, 4/11 (36%) alpha-subunit cell, and 1/11 (10%) follicle-stimulating hormone-luteinizing hormone cell adenomas. By contrast, all ten prolactin cell and seven growth hormone cell adenomas were c-kit negative. These data suggest that, in normal conditions, c-kit may be involved in the pituitary-adrenal axis regulation.

Merkel cell carcinoma frequently shows histologic features of basal cell carcinoma: a study of 30 cases

BACKGROUND

Merkel cell carcinoma (MCC) is a basaloid cutaneous neoplasm that may be mistaken for basal cell carcinoma (BCC).

METHODS

Thirty MCCs were examined for areas that histologically resembled BCC.

RESULTS

One of the histologic features of BCC (either a mucinous stroma or stromal artifactual retraction) was identified in all MCCs. A mucinous stroma was found in 28 MCCs (93%), stromal artifactual retraction in 27 (90%), mucin-containing gland-like spaces within tumor nests in 8 (27%), focal peripheral palisading in 8 (27%), epidermal involvement in 3 (10%) and dystrophic calcification in 1 MCC (3%). The cytologic features and absence of widespread peripheral palisading were the most reliable discriminators between MCC and BCC on routine sections. Squamous cell carcinoma was identified in four cases (13%). Two cases (7%) contained pagetoid intraepidermal spread (IES) of MCC. In one case, there was IES over the entire epidermal surface associated with intranuclear clearing, resembling the intranuclear cytoplasmic inclusions (INI) common in melanocytic tumors. INI were identified in six MCCs (20%).

CONCLUSIONS

MCCs frequently contain areas that histologically resemble BCC and other more common cutaneous malignancies. This can lead to diagnostic errors, particularly in small fragmented curettage specimens or frozen sections.

Merkel cell carcinoma metastasizing to the kidney mimicking primary neuroendocrine renal cancer

A 56-year-old male with a history of cutaneous neuroendocrine (Merkel cell) carcinoma presented with a solid mass of the left kidney, measuring 10 cm in largest diameter. On histology, the tumour was composed of loosely packed uniform cells with round-to-oval nuclei and scant cytoplasm. Immunohistochemically, the tumour cells diffusely expressed pancytokeratin and neuroendocrine markers, such as chromogranin A, synaptophysin and CD56 (NCAM). Distinct paranuclear dot-like expression of cytokeratin 20 showed the lesion to be metastatic Merkel cell carcinoma. This is the first reported case of Merkel cell carcinoma metastatic to the kidney mimicking primary neuroendocrine renal cancer. We discuss the differential diagnosis of the tumour and perform a systematic literature review, including potential indications for renal tumour biopsy in patients with a history of nonrenal malignancy.

Ovarian nonsmall cell neuroendocrine carcinoma: a clinicopathologic and immunohistochemical study of 11 cases

Nonsmall cell neuroendocrine carcinoma (NSCNEC) of the ovary is a rare and aggressive tumor commonly associated with other surface epithelial and germ cell neoplasms. In this study, we present the clinicopathologic and immunohistochemical features of 11 such cases seen at The University of Texas M.D. Anderson Cancer Center in a 16-year period (1990 to 2005). Patients ranged in age from 22 to 63 years (mean 46.7). The most common presentation was abdominal/pelvic pain (6 cases), followed by ascites (2 cases), pelvic mass, vaginal bleeding, and abdominal bloating (1 case each). Tumors were mostly unilateral, cystic, or solid/cystic and ranged in size from 5 to 26 cm (mean 16.2). In 8 cases, NSCNEC was associated with other epithelial neoplasms, including mucinous neoplasms of low malignant potential, mucinous carcinoma, endometrioid carcinoma, mixed endometrioid and mucinous carcinoma, and a high-grade carcinoma, not otherwise specified. In 2 cases, the tumor was associated with a mature cystic teratoma; one of them also containing an invasive moderately differentiated adenocarcinoma. A single case was associated with a benign ovarian cyst. The latter case had a dermoid cyst in the contralateral ovary. NSCNEC represented anywhere from 10% to 90% of the ovarian tumor. Microscopically, the neuroendocrine component was usually composed of large and/or intermediate oval to round cells. In 2 cases, the intermediate cells were intermixed with small cells. Three cases had also spindle cells. The neoplastic cells were mostly arranged in a solid pattern, nests, or trabeculae. All tumors had a brisk mitotic activity. Immunoperoxidase studies for keratin cocktail, cytokeratin (CK) 7, CK20, CAM 5.2, chromogranin A, synaptophysin, NSE, CD56, and c-kit were performed and the cases stained as follows: keratin cocktail 6/6, CK7 4/5, CK20 3/5, CAM 5.2 3/3, chromogranin A 8/11, synaptophysin 9/9, NSE 1/1, CD56 4/8, and c-kit 5/7. According to the International Federation of Gynecology and Obstetrics staging system, 4 cases were stage I tumors, 3 cases were stage III tumors, and 4 cases were stage IV tumors. Seven patients were treated with total abdominal hysterectomy and bilateral salpingo-oophorectomy followed by chemotherapy. One patient had a bilateral salpingo-oophorectomy with omentectomy and appendectomy followed by chemotherapy; 1 patient had a total abdominal hysterectomy with right salpingo-oophorectomy followed by chemotherapy; one had a bilateral salpingo-oophorectomy followed by chemotherapy, and one had a right salpingo-oophorectomy with appendectomy followed by chemotherapy. Five patients died of disease at 2, 3, 9, 20, and 36 months. One patient is alive with disease at 8 months and 5 are alive without evidence of disease at 11, 28, 37, 66, and 68 months. Four of 5 patients who died of disease had either stage III or IV tumors and 3 of 5 patients who are alive without evidence of disease have stage I tumors. In summary, ovarian NSCNEC is an aggressive tumor with a tendency to present at advanced stage and cause death within a mean of 17 months after diagnosis; however, some patients, particularly those with stage I disease and/or those who have received platinum-based therapy, may have a more favorable prognosis.

Primary cutaneous neuroendocrine cell carcinoma (Merkel cell carcinoma) with prominent microcystic features, mimicking eccrine carcinoma

Although primary cutaneous neuroendocrine cell carcinoma [Merkel cell carcinoma (MCC)] may show divergent features, including microcystic ('tubuloglandular'), squamous, eccrine and rhabdomyoblastic, a diffuse microcystic pattern is exceedingly rare. In this study, we present two cases of MCC with prominent microcystic features, which precluded a definitive diagnosis in the initial punch biopsy. Both patients were middle-aged men with a history of rapidly growing plaques of the back or posterior neck. Punch biopsies from both patients revealed an infiltrating neoplasm with prominent microcystic features that mimick tubuloglandular structures, lined by hyperchromatic basaloid cells, which were strongly positive for chromogranin and BerEP4, variably positive for CK7 and CK5/6 and negative for CK20, synaptophysin, S-100, epithelial membrane antigen (EMA), gross cystic disease fluid protein-15 (GCDFP-15), estrogen/progesterone receptors (ER/PR), thyroid transcription factor 1 (TTF1) and carcinoembryonic antigen (CEA). The re-excision specimens showed a multifocal intra-epidermal component in one case and typical finely stippled nuclear chromatin in both cases. Although the lack of CK20 staining is unusual, the histologic characteristics along with the remaining immunohistochemical studies favor the diagnosis of a primary cutaneous neuroendocrine cell carcinoma over the variants of eccrine carcinoma or basal cell carcinoma with neuroendocrine differentiation. Our cases illustrate that prominent microcystic features, mimicking glandular differentiation, may occur in MCC and pose a diagnostic challenge in small biopsy specimens.

Clinical significance of p16INK4a and p53 overexpression in endocrine tumors of the gastrointestinal tract

This study was designed to determine the expression of p16, p53, and CD117 in gastrointestinal tract endocrine tumors. Immunohistochemical studies of p16, p53, and CD117 were performed in 57 gastrointestinal tract endocrine tumors, including 22 poorly differentiated endocrine carcinomas (PDECs) and 35 well-differentiated endocrine tumors (WDETs). Overexpression of p16 and p53 was observed in 16 (73%) and 10 (45%) of the PDECs, respectively, whereas only 1 WDET showed overexpression of p53 and none showed overexpression of p16. A total of 18 (82%) of the PDECs showed overexpression of p16 or p53 proteins. This is closely associated with PDEC (P < .0001). By using overexpression of p16 or p53 as the criteria for PDEC, the sensitivity and specificity are 81.8% and 97.1%, respectively, with positive and negative predictive values of 94.7% and 89.5%, respectively. CD117 was not detected in any of the 57 gastrointestinal endocrine tumors by immunohistochemical analysis.

[Immunohistochemistry in ophthalmic pathology: applications and limitations]

We evaluate the applications of immunohistochemistry (IHC) in ophthalmic cytology and pathology. The principles of the techniques used in IHC are described. Recent improvements are highlighted, such as the polymeric labeling two-step method, tyramine signal amplification, rabbit monoclonal antibodies, and labeled nanocrystals. The results of the immunohistochemical methods are collected in bacterial and viral diseases and in tumors of the eye and its adnexa, the pathology of which varies greatly. The results in lymphomas, melanomas, and palpebral tumors were more details for practical reasons. There are widespread applications of IHC in ophthalmic pathology, extending from viral ocular and general diseases to the diagnosis of tumors. In some conditions, this technique needs to be associated with molecular biology investigations. Automation helps establish standard protocols, but IHC is a multistep diagnostic method requiring proper selection, fixation, processing, and staining procedures. From a general standpoint, good communication between pathologists and ophthalmologists is the best guarantee of satisfying results.

Immunohistochemical distinction between merkel cell carcinoma and small cell carcinoma of the lung

We assessed the usefulness of several immunohistochemical stains in distinguishing these two neoplasms, including cytokeratin 7, cytokeratin 20 (CK20), neuron-specific enolase, chromogranin, synaptophysin, neurofilaments (NF), thyroid-transcription factor-1 (TTF-1), CD56 antigen, S-100 protein, vimentin, c-erbB-2 oncoprotein, and CD117 antigen. All 13 cases of Merkel cell carcinoma evaluated were positive for CK20, and negative for TTF-1. Twelve of 13 Merkel cell carcinoma cases were positive for NF. Eleven of 13 cases of small cell lung carcinoma were positive for TTF-1. All small cell lung carcinoma cases were negative for NF, and all but one were negative for CK20. In terms of the remaining antigens, there were no differences of significance between the two neoplasms. These findings suggest that a set of three immunohistochemical stains, including CK20, NF, and TTF-1, is useful in affording a distinction between Merkel cell carcinoma and small cell lung carcinoma.

KIT (CD117): a review on expression in normal and neoplastic tissues, and mutations and their clinicopathologic correlation

CD117 (KIT) is a type III receptor tyrosine kinase operating in cell signal transduction in several cell types. Normally KIT is activated (phosphorylated) by binding of its ligand, the stem cell factor. This leads to a phosphorylation cascade ultimately activating various transcription factors in different cell types. Such activation regulates apoptosis, cell differentiation, proliferation, chemotaxis, and cell adhesion. KIT-dependent cell types include mast cells, some hematopoietic stem cells, germ cells, melanocytes, and Cajal cells of the gastrointestinal tract, and neoplasms of these cells are examples of KIT-positive tumors. Other KIT-positive normal cells include epithelial cells in skin adnexa, breast, and subsets of cerebellar neurons. KIT positivity has been variably reported in sarcomas such as angiosarcoma, Ewing sarcoma, synovial sarcoma, leiomyosarcoma, and MFH; results of the last three are controversial. The variations in published data may result from incomplete specificity of some polyclonal antibodies, possibly contributed by too high dilutions. Also, KIT is expressed in pulmonary and other small cell carcinomas, adenoid cystic carcinoma, renal chromophobe carcinoma, thymic, and some ovarian and few breast carcinomas. A good KIT antibody reacts with known KIT positive cells, and smooth muscle cells and fibroblasts are negative. KIT deficiency due to hereditary nonsense/missense mutations leads to disruption of KIT-dependent functions such as erythropoiesis, skin pigmentation, fertility, and gastrointestinal motility. Conversely, pathologic activation of KIT through gain-of-function mutations leads to neoplasia of KIT-dependent and KIT-positive cell types at least in three different systems: mast cells/myeloid cells--mastocytosis/acute myeloid leukemia, germ cells--seminoma, and Cajal cells--gastrointestinal stromal tumors (GISTs). KIT tyrosine kinase inhibitors such as imatinib mesylate are the generally accepted treatment of metastatic GISTs, and their availability has prompted an active search for other treatment targets among KIT-positive tumors such as myeloid leukemias and small cell carcinoma of the lung, with variable and often nonconvincing results.

Cytology applications of p63 and TTF-1 immunostaining in differential diagnosis of lung cancers

The pathologic distinction of small cell from non-small cell-lung carcinoma is of considerable therapeutic significance. In particular, the ability to distinguish poorly differentiated non-small-cell lung cancer from small-cell lung carcinoma (SCLC) is at times difficult based upon morphology alone; available immunohistochemical markers such as neuroendocrine markers are of limited utility. We have demonstrated the role of p63 and thyroid transcription factor-1 (TTF-1) in the differential diagnosis of poorly differentiated squamous-cell carcinoma (PDSCC) versus SCLC, mostly in biopsy samples (Wu et al., American Journal of Clinical Pathology 2003;119:696-702). Here, we examine further the utility of this panel in cytologic cell-block samples of lung cancers including both primary and metastatic cancers of pulmonary origin, and cases of nonpulmonary cancers metastatic to lung in which differential diagnoses included a lung primary.Four-micron thick sections of 30 alcohol-fixed paraffin-embedded cell blocks from 14 lung FNAs, 6 liver FNAs, 3 bronchial washings, 1 subcarinal lymph node FNA, 1 iliac lymph node FNA, 1 pelvic mass FNA, 1 neck lymph node FNA, 1 adrenal FNA, and 1 pleural effusion were deparaffinized and stained with monoclonal antibodies reactive to p63 (1:800, Santa Cruz Biotechnology) and TTF-1 (1:50, Dako). Slides were stained for p63 using a streptavidin-biotin kit (BioGenex) and diaminobenzidine as chromagen, and counterstained with hematoxylin. Slides were stained for TTF-1 using a Dako Autostainer. Thirty cases were examined, including 8 primary SCLCs, 8 extra-pulmonary metastases of lung SCLCs, 4 PDSCCs and 4 primary pulmonary adenocarcinomas, and 6 nonpulmonary adenocarcinomas metastatic to lung or other sites. Fifteen out of 16 (94%) SCLC cases were p63-/TTF-1+, ranging in intensity from focal-weak to diffuse-strong; 1/16 SCLCs from a bronchial washing was p63-/TTF-1- but synaptophysin was positive. All 4 primary lung adenocarcinoma cases were p63-/TTF-1+; contrasting with nonpulmonary adenocarcinomas that were all p63-/TTF-1-. All 4 PDSCC cases were p63+/TTF-1-. The panel of p63 and TTF-1 appears to be useful in the diagnostic evaluation of cytologic cell-block samples of pulmonary malignancy.