Diagnosis of Sarcomatoid Melanoma by Surrogate Immunostains

Is Primary Poorly Differentiated Sarcomatoid Malignancy of the Parotid Gland Sarcomatoid Undifferentiated/Dedifferentiated Melanoma? Report of Three Unusual Cases Diagnosed by Fine-Needle Aspiration Combined with Histological, Immunohistochemical, and Molecular Analyses

INTRODUCTION

Poorly differentiated primary sarcomatoid parotid malignancies are extremely rare. These tumors have not been consistently studied by morphology, immunohistochemistry, or molecular techniques.

CASE PRESENTATION

We report three unusual cases of parotid gland poorly-differentiated sarcomatoid malignancy investigated by fine-needle aspiration and studied histologically, by immunohistochemistry and molecular investigations. Aspirates showed poorly specific polymorphous sarcomatoid malignancy in all cases. Histologically, all cases were polymorphous high-grade malignancies, and additionally, one case showed epithelial structures and was finally classified as salivary carcinosarcoma. Immunohistochemistry showed classical melanocytic markers negativity but positivity for PRAME, CD10, and WT1 in all three tumors and for CD56 in two tumors, which can potentially be supportive of melanocytic origin. Although not entirely specific, molecular characterization also suggested the melanocytic lineage of these tumors.

CONCLUSION

Although rare, primary malignant melanoma of salivary gland was already described, but undifferentiated/dedifferentiated amelanotic forms are unknown in this localization up today. Further case reports of similar presentations are required to confirm the unequivocal primary origin of these obscure neoplasms in the parotid gland.

Primary Undifferentiated/Dedifferentiated Cutaneous Melanomas-A Review on Histological, Immunohistochemical, and Molecular Features with Emphasis on Prognosis and Treatment

Diagnosing cutaneous melanoma is usually straightforward based on these malignancies' histopathological and immunohistochemical features. Nevertheless, melanomas can imitate various other neoplasms, sometimes lacking the expression of conventional melanocytic markers and expressing non-melanocytic ones. Furthermore, divergent differentiation is more often encountered in metastatic melanomas and is still poorly described in primary cutaneous melanomas, and little is known about these patients' prognosis and therapeutic approach. Therefore, we reviewed the literature on undifferentiated/dedifferentiated cutaneous melanomas, and we discuss the histological, immunohistochemical, and molecular profiles of undifferentiated/dedifferentiated cutaneous melanomas to understand these peculiar lesions better and improve their diagnostic algorithm. In addition to this, we also discuss how different genetic mutations may influence prognosis and become potential therapeutic targets.

Sarcomatoid Dedifferentiated Melanoma: The Diagnostic Role of Next-Generation Sequencing

ABSTRACT

Sarcomatoid dedifferentiated melanoma (SDDM) represents a diagnostic challenge as this cutaneous spindle cell melanoma lacks expression of classic melanocytic markers including S100, SOX10, Melan-A, HMB45, and MITF. The expression of the emerging melanoma marker preferentially expressed antigen in melanoma (PRAME) in SDDM is largely unknown. In this article, a case of SDDM arising in association with a nodular melanoma is highlighted. A 65-year-old man presented with a several week history of an ulcerated lesion on the right medial knee. A shave biopsy of the lesion revealed a biphasic neoplasm, which consisted of a centrally located poorly differentiated spindle cell component and an adjacent nodular component consisting of atypical melanocytes arranged in nests and fascicles. While the nodular component stained for S100, SOX10, and Melan-A, the spindle cell component failed to stain for these conventional melanocytic markers, only staining diffusely for CD10 and faintly for CD68. Both components stained for PRAME diffusely albeit less intensely within the spindle cell component. Next-generation DNA sequencing assay of the microdissected biphasic components revealed a shared mutation of NRAS. The results of the PRAME immunohistochemical stain and next-generation DNA sequencing assay facilitated in establishing the diagnosis of SDDM in association with nodular melanoma.

Evolution of a melanoma in situ to a sarcomatoid dedifferentiated melanoma

Sarcomatoid dedifferentiated melanoma (SDDM) is a recently recognized subtype of melanoma that stains diffusely for CD10 and lacks the expression of the usual melanocytic markers including S100, SOX10, MITF, and Melan A. Advances in next-generation DNA sequencing technology have facilitated the increased recognition of this rare, aggressive spindle cell melanoma. Herein, a case of relatively early lesion of SDDM arising in association with melanoma in situ is highlighted. A 72-year-old man with a history of previously treated melanoma in situ on the face five years prior presented with a new rapidly growing lesion within the scar of the treated site. A shave biopsy of the lesion revealed a centrally located 1.8-mm deep, poorly differentiated spindle cell neoplasm in association with an adjacent recurrent melanoma in situ. The spindle cell component stained diffusely for CD10, but failed to stain for S100, SOX10, and Melan-A while the melanoma in situ expressed all three melanocytic markers. Next-generation DNA sequencing assay revealed mutations in NF1, CDKN2A, TP53, and TSC1. A diagnosis of stage 2B SDDM arising in association with melanoma in situ was established based on the clinical context and genomic assay results.

A case report of metastatic giant sarcomatoid melanoma with BRAF V600E mutation: a complete response to targeted therapy

Sarcomatoid melanoma is an extremely rare pattern of malignant melanoma, and only few cases have been described throughout the literature. We herein report a case of a patient with newly diagnosed, metastatic giant sarcomatoid melanoma of the arm. The patient underwent surgical removal of the huge mass, and NGS sequencing demonstrated BRAF V600E mutation.

In view of histological, immunohistochemical and molecular findings, a combined BRAF/MEK inhibitor (BRAF/MEK-i) therapy was prescribed as first line treatment. A complete response (over one year) to targeted therapy was obtained, and no adverse events have been reported. The patient maintained a full range of shoulder and elbow movements, and she is able to live independently and resume her daily activities. We therefore recommend that all patients with undifferentiated melanomas, sarcomatoid cutaneous malignancies or other mesenchymal tumours, should undergo BRAFV600E mutation testing.

Uncommon Histopathological Variants of Malignant Melanoma. Part 2

Despite new horizons opened by recent advances in molecular pathology, histological evaluation still remains the diagnostic gold standard regarding cutaneous melanocytic neoplasms. Several histological variants of melanoma have been described, and their knowledge is crucial for accurate diagnosis and classification of cases with unusual clinico-pathological features. Uncommon histological variants of melanoma have been described based on a broad constellation of features, including architectural pattern, stromal alterations, cytological attributes, and other morphological properties. This review is aimed at providing an extensive discussion of unusual but distinctive histopathological variants of melanoma.