Primary cutaneous interdigitating dendritic cell sarcoma is a morphologic and phenotypic simulator of poorly differentiated metastatic melanoma: A report of 2 cases and review of the literature

Malignant Dendritic Cell Sarcomas in the Skin: 2 Cases of Rare Sarcoma Subtypes With Literature Review

ABSTRACT

Interdigitating dendritic cell sarcoma is a rare, aggressive hematological malignancy primarily originating in lymph nodes, with only 10 reported cases presenting in the skin (primary cutaneous interdigitating dendritic cell sarcoma). Past presentations showed erythematous nodules on the proximal extremities, back, or face. Morphologically, these neoplasms are similar to melanomas and other dendritic cell (DC) tumors, making their diagnosis difficult. Here, we present 1 case of primary cutaneous interdigitating dendritic cell sarcomas and another 1 of malignant indeterminate dendritic cell tumor (indeterminate DC sarcoma). The first case is an 83-year-old man who presented with recent ulceration and bleeding of an asymptomatic, slow growing lesion on his right thigh with biopsy revealing a large, well-circumscribed polypoid spindle cell tumor in the dermis with atypical cells with vesicular nuclei in a lymphoplasmacytic background and immunohistochemistry positivity for CD45, CD68, S100, and Cyclin D1. The second case is a 74-year-old man who presented with a progressively darkening and enlarging abdominal skin lesion with biopsy revealing a diffuse infiltrate of atypical poorly differentiated pleomorphic nuclear cells and immunohistochemistry positivity for S100, CD1a, CD56, CD43, cyclin D1, CD31, CD4, and BRAF V600E. Our findings contribute to expand the reported literature on primary cutaneous DC sarcomas.

Primary cutaneous interdigitating dendritic cell sarcoma (IDCS): Report of a new case and literature review

Interdigitating dendritic cell sarcoma is a very rare entity in the spectrum of histiocytic and dendritic cell neoplasms that mostly occurs in lymph nodes, generally presenting as solitary lymphadenopathy, but may affect every organ. Among extra nodal sites, cutaneous interdigitating dendritic cell sarcoma is exceedingly rare; to date, only 9 cases have been described in English literature. The mean age at diagnosis was 60 years, with a male-female ratio of 1,5 to 1; clinically, two different modalities of skin presentation have been reported: solitary, represented by a single red-brownish nodular lesion, or diffuse, characterized by multiple nodular lesions in one or more body districts. The extreme rarity of this sarcoma and its morphological similarity to other poorly differentiated tumors may lead to a delay in diagnosis; in particular, cutaneous localization may be difficult to differentiate from follicular dendritic cell sarcoma, Langerhans cell sarcoma, poorly differentiated squamous cell carcinoma and more generally sarcomatoid carcinoma, atypical fibroxanthoma, malignant melanoma and several sarcomas. Immunohistochemistry plays an important role in identifying this rare entity and formulating a correct histological diagnosis, fundamental requirement for choosing the best therapeutic approach. We report herein a further case of an 81-year-old Caucasian woman who presented to the Dermatology Department to remove an asymptomatic skin papule in the left temporal region, clinically diagnosed as dermatofibroma. The overall pathological and immunohistochemical features supported the diagnosis of a malignant dendritic cell tumor, consistent of interdigitating dendritic cell sarcoma.

A rare case of cutaneous interdigitating dendritic cell sarcoma

Interdigitating dendritic cell sarcomas (IDCSs) are aggressive tumors of dendritic cells, often presenting with lymphadenopathy. Fewer than 10 cases of primary cutaneous IDCS have been reported. Histopathologically, IDCS presents as atypical spindle cells with irregular nuclei, and therefore can be difficult to distinguish from melanoma, follicular dendritic cell sarcoma, and Langerhans cell tumors by H&E examination alone. We report a unique case of a man with cutaneous IDCS that was initially misdiagnosed as melanoma. Having previously undergone an excision of a reported "melanoma" on the neck, he presented with a new growth on the cheek. Histopathologic findings revealed an atypical dermal lymphohistiocytic infiltrate around vessels and cells forming nests along the dermal-epidermal junction. Immunohistochemical stains were strongly positive for S100, fascin, and lysozyme; on the other hand, CD1a, langerin, CD21, CD23, and SOX10 were negative. These immunohistochemical findings were consistent with IDCS, and the patient's prior biopsy specimen was then revisited. Similar staining revealed that lesion also to be a cutaneous IDCS. Follow-up imaging with PET scan was negative for metastases, supporting the diagnosis of primary cutaneous IDCS. Our findings contribute to the limited literature on cutaneous IDCS and highlight a potential pitfall in its diagnosis because of overlapping histopathologic features with melanoma.

Interdigitating Dendritic Cell Tumor of Submandibular Lymph Node: Case Report and Literature Review

Dendritic cells (DCs) are key arms of immune system, which act in antigen presenting processes, and are considered as a bridge between innate and adaptive immune responses. DCs are found in both lymphoid and non-lymphoid organs. They are called interdigitating dendritic cells (IDCs) in secondary lymphoid organs. IDCs lack lineage surface markers and are positive for S-100 and vimentin. IDC sarcoma (IDCS) is a very rare neoplasm, which mainly affects lymph nodes, though there are reports of extra-nodal involvement. IDCS is thought to have poor prognosis. Although there is no consensus on the treatment modalities, such options as radical surgery, chemotherapy, and radiotherapy are performed depending on severity and site of the lesion. In this study, we present a case of IDCS in a 53-year-old male with a history of several skin lesions and prior diagnoses of basal cell carcinoma (BCC), squamous cell carcinoma (SCC), and metatypical carcinoma (MTC).

SOX10 Immunostaining in granulomatous dermatoses and benign reactive lymph nodes

BACKGROUND

SOX10 immunostaining has been considered a highly sensitive and specific marker for melanoma. But there is evidence suggesting that SOX10 positive cells can be present in dermal scars. Therefore, we investigated whether non-melanocytic cell types present in chronic inflammatory processes or benign lymph nodes express SOX10.

METHODS

We retrospectively selected 20 benign lymph nodes and 20 cutaneous granulomatous dermatoses. SOX10, CD68, and Melan-A immunohistochemistry was performed in all cases.

RESULTS

Scattered SOX10 positivity was found in 85% of lymph nodes, specifically in subcapsular and medullary sinuses and in 85% of granulomatous dermatoses. In granulomatous dermatoses, the Melan-A stain did not label the scattered SOX10 positive cells and it was difficult to determine if CD68 was co-expressed on the SOX10 positive cells. In the lymph nodes, the SOX10 positive cells did not co-express Melan-A or CD68.

CONCLUSIONS

We report SOX10 positive cells detected in granulomatous dermatoses and benign lymph nodes. In lymph nodes, SOX10 positive cells were exclusively in subcapsular and medullary sinuses. Therefore, SOX10 is an excellent stain for evaluation of metastatic melanoma with the caveat that positivity in subcapsular and medullary sinuses can be of non-melanocytic origin; the use of additional melanocytic markers is recommended in this situations.

A case of interdigitating dendritic cell sarcoma studied by whole-exome sequencing

Interdigitating dendritic cell sarcoma (IDCS) is an aggressive neoplasm and is an extremely rare disease, with a challenging diagnosis. Etiology of IDCS is also unknown and most studies with only case reports. In our case, immunohistochemistry showed that the tumor cells were positive for S100, CD45, and CD68, but negative for CD1a and CD21. This study aimed to investigate the causative factors of IDCS by sequencing the protein-coding regions of IDCS. We performed whole-exome sequencing with genomic DNA from blood and sarcoma tissue of the IDCS patient using the Illumina Hiseq 2500 platform. After that, we conducted Sanger sequencing for validation of sarcoma-specific variants and gene ontology analysis using DAVID bioinformatics resources. Through comparing sequencing data of sarcoma with normal blood, we obtained 15 nonsynonymous single nucleotide polymorphisms (SNPs) as sarcoma-specific variants. Although the 15 SNPs were not validated by Sanger sequencing due to tumor heterogeneity and low sensitivity of Sanger sequencing, we examined the function of the genes in which each SNP is located. Based on previous studies and gene ontology database, we found that POLQ encoding DNA polymerase theta enzyme and FNIP1 encoding tumor suppressor folliculin-interacting protein might have contributed to the IDCS. Our study provides potential causative genetic factors of IDCS and plays a role in advancing the understanding of IDCS pathogenesis.

Interdigitating dendritic cell sarcoma: Clinicopathologic study of 8 cases with review of the literature

To investigate the clinicopathologic features and differential diagnoses of interdigitating dendritic cell sarcoma (IDCS), the clinical, morphological and immunohistochemical features of eight cases of IDCS were collected and analyzed. Three patients were males and five were females, the mean age and the median age were 56.5 years and 57 years respectively. Clinically, the majority of cases involved lymph nodes. Microscopically, neoplastic cells were spindle or ovoid, forming fascicles or whorls. Every case had active mitosis figures. Immunohistochemically, these neoplastic cells were consistently positive for S100, but negative for CD21 and specific B-cell and T-cell associated antigens. Follow-up results were available in 7 cases, of which 5 cases of localized lesions survived, 2 cases died of organ involvement. Interdigitating dendritic cell sarcoma is an extremely rare neoplasm, with inferior prognosis and without standard treatment regimen. IDCS has similar but unique clinicopathologic features and the differential diagnoses include other histiocytic and dendritic cell neoplasms and malignant melanoma.

Histiocytic and dendritic cell neoplasms: what have we learnt by studying 67 cases

Tumors derived from histiocytic and dendritic cells encompass a large and heterogeneous group of neoplastic and reactive conditions, and their diagnosis is challenging both for pathologists and clinicians. Diagnosis is based on morphological and phenotypical findings, but hybrid features are not uncommon. Furthermore, recent studies uncovered the molecular mechanisms driving some of these tumors, improving diagnostic adequacy, and providing the basis for effective therapeutic breakthroughs.Sixty-seven cases were submitted to the accessory cell and histiocytic neoplasms session at the European Association of Haematopathology/Society for Hematopathology workshop 2016 held in Basel, Switzerland. The cases included histiocytic sarcomas (HS), Langerhans cell tumors (LCT), Erdheim-Chester disease, interdigitating dendritic cell sarcomas (IDCS), indeterminate dendritic cell tumors (IND-DCT), follicular dendritic cell sarcomas, and blastic plasmacytoid dendritic cell neoplasms. Rosai-Dorfman disease and, more rare, conditions such as ALK-positive histiocytosis were also submitted. These cases illustrated classical and unexpected features at morphological, phenotypical, and molecular levels, providing a valuable compendium for pathologists confronting with these tumors.The paper summarizes the most notable features of every single group of diseases, with comments about the most challenging issues, in the attempt to provide practical indications for their recognition.