Fine-needle biopsy of metastatic melanoma: clinical use and new applications

Monitoring melanoma patients on treatment reveals a distinct macrophage population driving targeted therapy resistance

Resistance to targeted therapy remains a major clinical challenge in melanoma. To uncover resistance mechanisms, we perform single-cell RNA sequencing on fine-needle aspirates from resistant and responding tumors of patients undergoing BRAFi/MEKi treatment. Among the genes most prominently expressed in resistant tumors is POSTN, predicted to signal to a macrophage population associated with targeted therapy resistance (TTR). Accordingly, tumors from patients with fast disease progression after therapy exhibit high POSTN expression levels and high numbers of TTR macrophages. POSTN polarizes human macrophages toward a TTR phenotype and promotes resistance to targeted therapy in a melanoma mouse model, which is associated with a phenotype change in intratumoral macrophages. Finally, polarized TTR macrophages directly protect human melanoma cells from MEKi-induced killing via CD44 receptor expression on melanoma cells. Thus, interfering with the protective activity of TTR macrophages may offer a strategy to overcome resistance to targeted therapy in melanoma.

Diagnostic Accuracy of Image-guided Biopsies for Diagnosis of Metastatic Melanoma in a Real-life Setting

Early detection of melanoma metastasis is essential in order to initiate treatment and improve patient prognosis. The aim of this study was to determine the diagnostic accuracy of different image-guided biopsy techniques in patients with melanoma. A cohort study of patients diagnosed with melanoma who had undergone image-guided biopsies (ultrasound-guided fine-needle aspiration cytology, ultrasound-guided core-needle biopsy, computerized tomography--guided fine-needle aspiration cytology and computerized tomography-guided core-needle biopsy) to detect melanoma metastasis between 2004 and 2021 was conducted. The reference standard was histological confirmation and/or clinical-radiological follow-up. Sensitivity, specificity, positive and negative predictive values were calculated. A total of 600 image--guided biopsies performed on 460 patients were included for analysis. Locoregional lesions represented 459 (76.5%) biopsies, and 141 (23.5%) were distant lesions. Of the included biopsies, 49 (8.2%) were insufficient for diagnosis. Overall, sensitivity and specificity were 92% (95% confidence interval 89-94) and 96% (95% confidence interval 91-99), respectively. Sensitivity sub-analyses revealed lower diagnostic accuracy values in the lung, inguinal lymph nodes, and computerized tomography-guided lesions under 1 cm. Limitations include spontaneous metastasis regression and arbitrary minimum follow-up period. Image-guided biopsies in patients with melanoma have high sensitivity and specificity for detection of regional or distant metastasis. Tissue type, location and tumour burden may influence the diagnostic accuracy of the test.

Early expansion of CD38+ICOS+ GC Tfh in draining lymph nodes during influenza vaccination immune response

T follicular helper (Tfh) cells provide critical help to B cells during the germinal center (GC) reaction to facilitate generation of protective humoral immunity. Accessing the human lymph node (LN) to study the commitment of CD4 T cells to GC Tfh cell differentiation during in vivo vaccine responses is difficult. We used ultrasound guided fine needle biopsy to monitor recall responses in axillary LNs to seasonal influenza vaccination in healthy volunteers. Specific expansion of GC cell subsets occurred exclusively within draining LNs five days postvaccination. Draining LN GC Tfh and precursor-Tfh cells express higher levels of CD38, ICOS, and Ki67, indicating they were significantly more activated, motile, and proliferating, compared to contralateral LN cells. These observations provide insight into the early expansion phase of the human Tfh lineage within LNs during a vaccine induced memory response and highlights early LN immune responses may not be reflected in the periphery.

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Early response to influenza vaccine is characterized by expansion of GC cell subsets

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Specific expansion of CD38+ ICOS+ GC Tfh and Pre-Tfh occurs in draining LNs only

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Activated GC Tfh and Pre-Tfh are also proliferating, expressing high levels of Ki67

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Correlation between activated Pre-Tfh and activated c-Tfh suggests a potential origin

The use of cytological material in melanoma for programmed death ligand 1 immunostaining

OBJECTIVE

Interest in immune therapies has exploded since the 2014 approval of first-generation programmed cell death 1 blocking antibodies for use in advanced melanoma. Clinical trials have focused primarily on histological material as the gold standard for evaluating programmed death ligand 1 (PD-L1) by immunoperoxidase (IPOX) studies. Studies validating the use of cytological specimens in the assessment of PD-L1 by IPOX staining are needed to optimise tissue utilisation in complementary diagnostic testing.

METHODS

Twenty-three melanoma surgical biopsies (SBx) with an IPOX stain for PD-L1 clone 28-8, and a corresponding cytological specimen from the same patient, adequate for PD-L1 evaluation, were selected. Cell-transfer cell blocks (CBs) and conventional CBs were used to perform PD-L1 testing. Tumour proportion scores (TPS) were generated and the results were correlated with the corresponding SBx.

RESULTS

Overall agreement (OA) using a ≥1% TPS cut-off for SBx compared to CB was 88.9%, positive percent agreement (PPA) was 87.5%, and negative percent agreement (NPA) was 100%, OA using a ≥5% TPS cut-off was 55.6%, PPA was 42.9%, and NPA was 100%. SBx compared to cell-transfer CB using a ≥1% TPS cut-off had an OA of 65.2%, a PPA of 55.6%, and a NPA of 100%, while a ≥5% TPS cut-off generated an OA of 52.2%, a PPA of 35.7%, and a NPA of 77.8%.

CONCLUSION

Our results demonstrate that cytological material, particularly conventional CB, is a viable alternative for evaluating PD-L1 in melanoma cases and suggest that a lower threshold (≥1%) may be beneficial when evaluating cytological material.

A case of S-100 negative melanoma: A diagnostic pitfall in the workup of a poorly differentiated metastatic tumor of unknown origin

When confronted with a metastatic poorly differentiated tumor of unknown origin, the initial workup includes the standard panel of immunostains to rule out carcinoma, sarcoma, lymphoma, and the greatest mimicker in pathology - malignant melanoma. Although not specific, the S-100 protein is expressed in over 95% of malignant melanomas. Herein, we present a case of multiorgan metastatic malignancy with a dominant hilar and mediastinal mass in a current smoker; clinically, highly suggestive of widespread primary lung cancer. This case was eventually classified as malignant melanoma, despite a significant diagnostic challenge due to lack of prior history, unusual cytomorphology, and S-100 protein negativity. A battery of immunostains was performed and the addition of other melanocytic-associated markers confirmed the melanocytic lineage of the neoplasm. This case highlights the pitfalls in the differential diagnosis of a metastatic tumor of unknown origin by fine needle aspiration cytology due to the significant morphologic overlap of poorly differentiated malignancies. We emphasize that, albeit rare, malignant melanomas can be completely negative for S-100 protein and the use of additional melanocytic-associated markers in the differential workup maybe critical in arriving promptly at a proper diagnosis. We also briefly discuss other currently available immunohistochemical markers that can assist in the identification of the S-100 negative melanoma.

TORC1 suppression predicts responsiveness to RAF and MEK inhibition in BRAF-mutant melanoma

RAF and MEK (mitogen-activated or extracellular signal-regulated protein kinase kinase) inhibitors are effective in treating patients with BRAF-mutant melanoma. However, most responses are partial and short-lived, and many patients fail to respond at all. We found that suppression of TORC1 activity in response to RAF or MEK inhibitors, as measured by decreased phosphorylation of ribosomal protein S6 (P-S6), effectively predicted induction of cell death by the inhibitor in BRAF-mutant melanoma cell lines. In resistant melanomas, TORC1 activity was maintained after treatment with RAF or MEK inhibitors, in some cases despite robust suppression of mitogen-activated protein kinase (MAPK) signaling. In in vivo mouse models, suppression of TORC1 after MAPK inhibition was necessary for induction of apoptosis and tumor response. Finally, in paired biopsies obtained from patients with BRAF-mutant melanoma before treatment and after initiation of RAF inhibitor therapy, P-S6 suppression predicted significantly improved progression-free survival. Such a change in P-S6 could be readily monitored in real time by serial fine-needle aspiration biopsies, making quantitation of P-S6 a valuable biomarker to guide treatment in BRAF-mutant melanoma.

Cytodiagnosis of erosive melanoma and basal cell carcinoma of the skin using cutaneous tissue smear

BACKGROUND

Cytomorphological assessment of erosive skin tumours offers a rapid and minimally invasive way to obtain a diagnosis. However, the studies so far conducted on this method have been relatively small.

AIM

To conduct a large retrospective study on cytomorphological assessment of erosive skin tumours.

METHODS

In this study, 86 cytological smears prepared from erosive cutaneous tumours clinically suspicious for melanoma were examined to test the diagnostic accuracy and practicability of cytomorphological evaluation of such tumours, and to compare the assessments of two investigators with different experience levels. In a subgroup of tumours, cytological assessment was compared with dermoscopic evaluation.

RESULTS

There was agreement in the cytological and histopathological results for 68 of 86 cases (79%) assessed by the experienced investigator and in 64 of 86 cases (74%) assessed by the inexperienced investigator. The diagnosis was confirmed cytologically in 39 and 34 of 42 melanomas, and in 28 and 27 of 35 basal cell carcinomas, respectively. The sensitivity of the cytodiagnosis was not significantly different between the two investigators. The dermoscopic evaluation showed good agreement with the cytological results for melanoma (82.4%), although use of dermoscopy was only possible for 49.9% of the lesions because of difficulties with the samples.

CONCLUSIONS

Cytological assessment of erosive melanoma and BCC lesions is a useful tool for gaining additional information on clinically uncertain skin tumours, and shows good agreement between different investigators.

Molecular diagnostics of melanoma fine-needle aspirates: a cytology-histology correlation study

Patients with advanced-stage melanoma harboring a BRAF mutation are candidates for BRAF inhibition as a therapeutic strategy. The use of fine-needle aspiration (FNA) to diagnose metastatic melanoma is increasing. Studies examining the predictive value of BRAF mutation analysis on melanoma FNAs via correlation with follow-up excision findings are lacking. We examined 37 consecutive FNA cases of metastatic melanoma in which the aspirated lesion was subsequently excised. DNA was purified from Diff-Quik-stained FNA smears and tissue blocks from corresponding excisions in parallel. BRAF mutation status was successfully obtained from both specimen types in 34 (92%) of 37 cases. BRAF mutations were detected in 12 (35%) of 34 cases-11 V600E and 1 V600K. Results of BRAF mutational analysis were concordant in all 34 FNA smear/tissue excision pairs. Thus, melanoma FNA for molecular diagnostics represents a rapid, minimally invasive, and effective management strategy in this era of precision medicine.

Thyroid cyst wall atypia in a patient with a history of malignant melanoma: a pitfall in fine-needle aspiration cytology

We present an interesting case report from a patient with a history of desmoplastic malignant melanoma (MM), who presented with a thyroid nodule. The patient's clinical diagnosis included a benign thyroid nodule versus a primary thyroid malignancy or metastatic MM. Fine-needle aspiration biopsy showed highly atypical spindle cells suspicious for metastatic MM. The acellular cell block prevented further studies such as immunohistochemical analysis. The patient underwent surgical excision of the mass, which showed a benign cystic thyroid nodule with an atypical cyst lining. Here, we report the presence of atypical cyst-lining cells in a patient with diagnosis of MM. The atypical cytology of the cyst-lining cells has been reported in the English literature; however, presence of significant cytological atypia, especially in a patient with a history of another malignancy, can be problematic. The cytopathologist should be aware of this entity and its diagnostic pitfalls.

Cytologic features of epithelioid hemangioendothelioma

To determine cytologic features of epithelioid hemangioendothelioma (EHE) that would enable accurate diagnosis, we evaluated fine-needle aspiration biopsy (FNAB) smears from 11 histologically confirmed EHEs. The variably cellular smears comprised dispersed single cells and occasional cell aggregates. Dense stromal fragments were present in association with some tissue fragments. The cells were epithelioid, containing moderate or large amounts of dense cytoplasm. Nuclei exhibited mild pleomorphism, and nuclear grooves were identified in all cases. At least occasional intranuclear pseudoinclusions (INPIs) and intracytoplasmic lumina (ICLs) were present in all cases and in 9 cases (82%), respectively, and rare erythrocytes were seen within ICLs in 5 cases (45%). Mitotic figures were identified in 4 cases (36%). The background was bloody in 6 cases (55%) and contained hemosiderin and/or hemosiderin-laden macrophages in 5 cases (45%). The combination of the following features in FNAB samples should raise strong suspicion for EHE: predominantly dispersed single cells with occasional cohesive cell clusters; epithelioid cytomorphology; dense cytoplasm with well-defined cytoplasmic borders; ICLs (with or without erythrocytes), INPIs, and nuclear grooves. The presence of these features should prompt correlation with clinical, radiologic, and histologic features and immunohistochemical evaluation using vascular markers.

Melanoma pathology: important issues for clinicians involved in the multidisciplinary care of melanoma patients

Histologic analysis remains the gold standard for diagnosis of melanoma. The pathology report should document those histologic features important for guiding patient management, including those characteristics on which the diagnosis was based and also prognostic factors. Pathologic examination of sentinel lymph nodes provides very important prognostic information. New techniques, such as comparative genomic hybridization and fluorescence in situ hybridization are currently being studied to determine their usefulness in the diagnosis of melanocytic lesions. Recent molecular studies have opened new avenues for the treatment of patients with metastatic melanoma (ie, targeted therapies) and molecular pathology is likely to play an important role in the emerging area of personalized melanoma therapy.

Fine-needle aspiration for proteomic study of tumour tissues

Fine-needle aspiration (FNA) is a technique largely applied in the diagnosis of tumours. FNA is a safe diagnostic procedure that is widely employed in the examination of masses at relatively low cost and minimal risk to the patient. In this review, we report on the state-of-the-art and the potential role of FNA to search for protein biomarkers by the proteomic approach.