Spindle cell lipoma (SCL) is a benign adipocytic tumor that primarily occurs in the subcutis of the posterior neck, upper back, and shoulder, particularly of middle-aged males. SCL and pleomorphic lipoma (PL) represent a morphological spectrum of one disease process. The lesion typically presents as a relatively small (<5 cm), mobile, slow-growing, painless mass. Magnetic resonance imaging reveals the lesion to be a well-defined subcutaneous mass with a mixture of adipose and non-adipose components. Intense enhancement of the non-adipose component is seen after contrast administration. Histologically, SCL is composed of variable distributions of mature adipocytes, bland spindle cells and ropey collagen bundles and PL also contains pleomorphic and multinucleated floret-like giant cells. By immunohistochemistry, the spindle and pleomorphic/floret-like giant cells of SCL/PL are diffusely positive for CD34 and show loss of nuclear RB transcriptional corepressor 1 (RB1) expression. Recent cytogenetic and molecular genetic studies have shown heterozygous deletions of 13q14, including the RB1 gene. SCL/PL can be successfully treated with simple excision, with a very low recurrence rate. Knowledge of these peculiar tumors is important because it can mimic a variety of benign and malignant soft-tissue tumors. This review provides an updated overview of the clinical, radiological, histopathological, cytogenetic, and molecular genetic features of SCL/PL.

Different authors have recently described a subtype of lipoma characterized by variation of adipocyte size, single cell fat necrosis, and a subset with minimal to mild nuclear atypia, and termed these as anisometric cell/dysplastic lipoma (AC/DL). These lipomas follow a benign course and rarely recur. In 3 examples, AC/DL has occurred in patients with childhood retinoblastoma (RB). We report another such example where multiple AC/DL occurred in the neck and back of a 30-year-old male who had germline RB1 gene deletion and bilateral RB in infancy. On excision, all tumors histologically showed similar morphology of adipocyte anisometry, focal single cell necrosis with surrounding binucleated or multinucleated histiocytes, hyperchromatic and minimally atypical lipocyte nuclei, vacuolated Lockhern change, rare foci of fibromyxoid change, occasional mononuclear cell clusters around capillaries, and loss of RB1 immunostaining. Unequivocal atypical cells, lipoblasts, floret-nucleated or multinucleated giant cells were absent. Molecular analysis of tumor cells showed monoallelic RB1 gene loss without amplification of MDM2 and CDK4 genes. Short-term follow up did not show tumor recurrence. AC/DLs in RB survivors are characterized by multiplicity, unifying histology, and benign course. Their biology appears distinct from ordinary lipomas, spindle cell lipomas, and atypical lipomatous tumors.

Treatment of advanced non-small cell lung cancer (NSCLC) patients with epidermal growth factor receptor (EGFR) mutation with EGFR-tyrosine kinase inhibitors (EGFR-TKIs) can achieve good disease control, but it will inevitably produce drug resistance. About 3%-10% of the resistance mechanism is small cell transformation. Two cases of stage IV lung adenocarcinoma with EGFR mutation were reported and the disease was controlled after EGFR-TKIs treatment. In case 1, progression-free survival (PFS) before small cell carcinoma transformation was 16 months, and in case 2, PFS before small cell carcinoma transformation was 24 months. Subsequent biopsy after disease progression indicated a shift to small cell lung cancer. Case 1 PFS after small cell carcinoma transformation was 6 months, and case 2 PFS after small cell carcinoma transformation was 8 months, and overall survival (OS) was 36 months, which significantly prolonged the patient\'s survival. At the same time, the literature of such drug resistance mutations was reviewed. For patients with advanced NSCLC with sensitive mutations, it is necessary to conduct secondary histopathological tests after TKIs treatment resistance, and select subsequent treatment according to different resistance mechanisms for the whole course of disease management.
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【中文题目：晚期肺腺癌靶向耐药后
小细胞癌转化2例并文献复习】 【中文摘要：具有表皮生长因子受体（epidermal growth factor receptor, EGFR）敏感突变的晚期非小细胞肺癌（non-small cell lung cancer, NSCLC）患者应用EGFR酪氨酸激酶抑制剂（EGFR-tyrosine kinase inhibitors, EGFR-TKIs）治疗可取得良好的疾病控制，但不可避免会产生耐药。其中3%-10%左右的耐药机制为小细胞癌转化。本文报道2例IV期肺腺癌存在EGFR突变、经EGFR-TKIs治疗后疾病得到控制的病例。病例1发生小细胞癌转化前的无进展生存期（progression-free survival, PFS）为16个月，病例2发生小细胞癌转化前的PFS为24个月。疾病进展后再次活检提示小细胞癌转化。经后续治疗再次稳定，病例1发生小细胞癌转化后的PFS为6个月，总生存期（overall survival, OS）暂未出现，病例2发生小细胞癌转化后的PFS为8个月，OS为36个月，显著延长了患者生存。同时对此类耐药突变进行文献复习。对于晚期NSCLC存在敏感突变的患者，经EGFR-TKIs治疗耐药后进行二次组织病理检测，根据不同耐药机制选择后续治疗对疾病全程管理十分必要。
】 【中文关键词：小细胞癌转化；EGFR基因突变；RB1；TP53】.

The classification of soft tissue tumors has evolved considerably in the last decade, largely due to advances in understanding the pathogenetic basis of many of these, sometimes rare, tumors. Deletion of Retinoblastoma 1 (RB1), a well-known tumor suppressor gene, has been implicated in the tumorigenesis of a particular group of soft tissue neoplasms. This group of so-called \"RB1-deleted soft tissue tumors\" has been rapidly expanding in recent years, currently consisting of spindle cell/pleomorphic lipoma, atypical spindle cell/pleomorphic lipomatous tumor, pleomorphic liposarcoma, myofibroblastoma, cellular angiofibroma, and acral fibromyxoma. Most of these neoplasms, except pleomorphic liposarcoma, are considered benign entities and are mainly described in the older adult population. This article will review the currently known morphological, immunohistochemical, and molecular features of this heterogeneous group of mesenchymal tumors with an emphasis on differential diagnosis.

Hereditary cancer predisposition syndromes (HCS) become more recognizable as the knowledge about them expands, and genetic testing becomes more affordable. In this review, we discussed the known HCS that predispose to central and peripheral nervous system tumors. Different genetic phenomena were highlighted, and the important cellular biological alterations were summarized. Genetic mosaicism and germline mutations are features of HCS, and recently, they were described in normal population and as modifiers for the genetic landscape of sporadic tumors. Description of the tumors arising in these conditions was augmented by representative cases explaining the main pathological findings. Clinical spectrum of the syndromes and diagnostic criteria were tabled to outline their role in defining these disorders. Interestingly, precision medicine has found its way to help these groups of patients by offering targeted preventive measures. Understanding the signaling pathway alteration of mammalian target of rapamycin (mTOR) in tuberous sclerosis helped introducing mTOR inhibitors as a prophylactic treatment in these patients. More research to define the germline genetic alterations and resulting cellular signaling perturbations is needed for effective risk-reducing interventions beyond prophylactic surgeries.

In this Annual Review Issue of The Journal of Pathology, we present 15 invited reviews on topical aspects of pathology, ranging from the impacts of the microbiome in human disease through mechanisms of cell death and autophagy to recent advances in immunity and the uses of genomics for understanding, classifying and treating human cancers. Each of the reviews is authored by experts in their fields and our intention is to provide comprehensive updates in specific areas of pathology in which there has been considerable recent progress. Copyright © 2019 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

BACKGROUND: The 13q deletion syndrome is a rare chromosome disorder associated with wide phenotypic spectrum, which is related to size and location of the deleted region and includes intellectual disability, growth retardation, craniofacial dysmorphisms, congenital malformations, and increased risk of retinoblastoma.
METHODS: Here, we report on a teenage boy with a mild phenotype characterized by obesity, hyperactivity, dysphagia, dysgraphia, sleep disturbance, and minor dysmorphic features (round face, bushy eyebrows, and stubby hands). Array Comparative Genomic Hybridization on blood identified a mosaic 13q14.13-13q31.1 deletion, with a mosaicism rate around 40%, which was confirmed by quantitative PCR and interphase Fluorescent In Situ Hybridization (iFISH) on both blood genomic DNA and cultured/uncultured blood lymphocytes, respectively. Conversely, karyotype analysis on blood estimated a mosaicism rate of 24% and iFISH on buccal smears revealed a borderline value of 0.4%, suggesting the absence of 13q deletion in this cell line.
CONCLUSIONS: The comparison with previous patients carrying similar deletions informed that the proband clinical presentation is the mildest reported to date, thus supporting the burden of mosaicism in modulating the phenotype also in case of large chromosomal rearrangements. Characterization of further cases by in-depth mosaicism rate in tissues with different embryonic origins might contribute in the future to a better definition of genotype-phenotype correlation, including tumor risk.

The term \"anisometric cell lipoma\" (ACL) has been proposed recently by Evans for a lipoma variant characterized by striking variation in size and shape of adipocytes but little or no cytological atypia. One patient with multiple ACL had a history of retinoblastoma. The current study analyzed six patients with ACL (4 males and two females aged 34 to 87years; median, 58); all seen in consultation. Five patients presented with solitary and one with multiple subcutaneous masses measuring 5 to 9cm (median, 7.5cm). Affected sites were upper arm (3), shoulder (2), neck (1), trunk (1) and chest wall (1). Surgical excision was the treatment in all cases. No recurrence was recorded at last follow-up (1-17months). Submitted diagnoses were atypical lipomatous tumor (n=3), lipoma with regressive changes (n=1) and unclassified lipomatous neoplasm (n=2). In all cases, the striking variation in size of adipocytes was mentioned as the most or sole worrisome feature justifying external consultation. Histology was similar in all cases. All fulfilled the features reported by Evans as stated above and lacked any conventional spindle cell lipoma-like areas. Multi-vacuolated (lipoblast-like) cells were seen in three cases. MDM2/CDK4 were negative by immunohistochemistry and MDM2 amplification was absent by FISH in all cases. RB1 immunoexpression was lost in 5/5 cases. Rb1 FISH analysis revealed copy number aberrations in 3 of 4 cases (heterozygous deletions in two cases and homozygous deletion in one). In conclusion, ACL shares similar clinicopathological, demographic and molecular features as spindle cell lipoma suggesting related diseases. In the light of the available literature on adipocytic neoplasms in retinoblastoma survivors (>30 patients with multiple lipomas following retinoblastoma reported), it is probably that retinoblastoma-associated lipomas belong to the ACL category. Thus, it seems that Somatic RB1 loss probably drives sporadic ACL in a comparable way to post-retinoblastoma lipomas which were shown to be driven by LOH of the RB1 wild-type allele.