Histiocytic and Dendritic Cell Sarcomas



Histiocytic and Dendritic Cell Sarcomas


Archana Shenoy

Louis P. Dehner



INTRODUCTION

The subject of histiocytic lesions of the skin is a topic usually dominated by Langerhans cell histiocytosis and juvenile xanthogranuloma, both regarded as clonal proliferations and benign in the usual clinical sense of treatment response and limited disease progression, if any. However, in the setting of multifocal and generally organ-based lesions, both may behave in a clinically aggressive fashion despite their morphologically innocuous appearance.

Another histiocytic lesion of the skin is the common dermatofibroma and its several histiocytic variants which are thought to be derived from the dermal dendrocyte. This category of dermal-based neoplasms may have a considerable degree of nuclear pleomorphism and an unsettling degree of mitotic activity, but in the absence of anaplasia and atypical mitotic figures. There is some degree of overlapping histologic features between dermatofibroma and juvenile xanthogranuloma, which is not surprising given that the dermal dendrocyte is regarded as the common progenitor.

Unequivocal malignant neoplasms of monocyte/macrophage lineage are in general very uncommon to rare regardless of their primary site. The skin is just one of the several reported sites, and in some cases, multifocal tumors are apparent on clinical presentation.

The past “malignant histiocytosis” was a diagnosis that today is recognized as anaplastic large cell lymphoma (ALCL) and lymphomatoid papulosis, which are CD30 T-cell proliferations, and with the presence of ALK-1 translocation in subsets of ALCL. Also regarded as malignant histiocytosis in the past was histiocytic medullary reticulosis of Scott and Robb-Smith, which is recognized today as primary or secondary hemophagocytic lymphohistiocytosis or macrophage activation syndrome.

Before a diagnosis of a malignant histiocytic lesion is made in the skin or elsewhere, it is right to keep in mind that reactive histiocytes can acquire a marked degree of atypia with nuclear enlargement, hyperchromatism, and mitotic activity.

Through the application of a series of well-characterized membrane and cytoplasmic markers, various groups or clusters of antigens are exposed by antigen processing and antigen presenting mononuclear bone marrow–derived cells which are ubiquitously distributed in virtually organs but have a specific localization in some organs such as the liver, spleen, and lymph nodes or a more random or diffuse dispersion in other sites such as the skin and supporting soft tissues.

Malignant cutaneous neoplasms of the monocyte/macrophage lineage can be broadly classified into histiocytic and dendritic cell neoplasms, as tumors of antigen processing or presenting function, based on their morphology, immunophenotype, and ultrastructural characteristics.1,2 There are four distinct diagnostic categories: (i) histiocytic sarcoma (HS); (ii) follicular dendritic cell sarcoma (FDCS); (iii) interdigitating dendritic cell sarcoma (IDCS); and (iv) indeterminate dendritic cell sarcoma (INDCS) (Table 71-1). The exact cell of origin of some of these neoplasms remains the subject of continued study and discussion without a consensus or resolution in all cases. Some authors also classify Langerhans cell proliferations under this diagnostic umbrella, which have been discussed in depth in Chapter 67. Hematolymphoid malignancies of lymphocytic (T and B) lineage are almost always considered in the differential diagnosis and laboratory workup, before arriving at a final diagnosis of these rare neoplasms.








TABLE 71-1 Salient Features of Histiocytic and Dendritic Cell Sarcoma




























































































































HS


FDCS


IDCS


INDCS


Clinical findings


Solitary or multiple cutaneous lesions


Asymptomatic lymph node lesion, solitary or multiple


Papules, nodules, and plaques on skin


Skin rash


Rare cutaneous involvement


Morphology


Discohesive epithelioid-spindle cells


Spindle to epithelioid cells with whorls


Epithelioid cells with nuclear grooves and clefts


Immunophenotype



CD68


+


+/−


+/−


+/−



CD163


+


N/A


N/A


N/A



Lysozyme


+


N/A


N/A


N/A



CD1a


−/+




+/−



S100


−/+


+/−


+


+



CD21



+





CD23



+





CD35



+





CD4





+


Ultrastructural characteristics



Cytoplasmic processes


Absent


Numerous, slender


Interdigitating, complex


Interdigitating, complex



Desmosomes


Absent


Mature


Absent


Absent



Birbeck granules


Absent


Absent


Absent


Absent



Lysosomes


Abundant


Sparse


Scattered


Unknown


HS, histiocytic sarcoma; FDCS, follicular dendritic cell sarcoma; IDCS, interdigitating dendritic cell sarcoma; INDCS, indeterminate dendritic cell sarcoma.


Adapted with modifications from Dalia S, Shao H, Sagatys E et al. Dendritic cell and histiocytic neoplasms: biology, diagnosis, and treatment. Cancer Control. 2014;21(4):290–300. Republished with permission by Cancer Control: Journal of the Moffitt Cancer Center.



HISTIOCYTIC SARCOMA

Nov 8, 2018 | Posted by in PATHOLOGY & LABORATORY MEDICINE | Comments Off on Histiocytic and Dendritic Cell Sarcomas
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