Cutaneous Rhabdomyosarcoma

 Embryonal, alveolar, pleomorphic, and epithelioid types of RMS have been described as primary cutaneous tumors






Clinical Issues




• Very rare
image Cutaneous metastases or secondary involvement of skin by deep primary must be thoroughly excluded

• Bimodal age distribution
image Children and young adults: Embryonal and alveolar types

image Older adults: Plemorphic and epithelioid types

• May occur at any cutaneous site

• Limited data available regarding treatment and prognosis
image However, recurrences and metastases reported


Microscopic




• Confined to dermis &/or subcutaneous tissue
• Embryonal rhabdomyosarcoma (RMS)

image Variably cellular sheets of spindle and ovoid cells

image Myxoid stroma common

• Alveolar RMS
image Nests of small round cells with fibrous septa

image Multinucleated tumor giant cells (“wreath cells”) may be present

• Pleomorphic RMS
image Sheets of markedly pleomorphic, atypical cells

image May show rhabdoid morphology

• Epithelioid RMS
image Sheets of uniform epithelioid cells with abundant eosinophilic cytoplasm

image Eccentric nuclei with prominent nucleoli


Ancillary Tests




• Desmin (+), myogenin (+), MYOD1(+)

• Focal keratin (+) reported

• Negative for S100, SOX10, p63, CD31, melanocytic markers


Top Differential Diagnoses




• Superficial Ewing sarcoma/PNET

• Carcinoma, melanoma

• Merkel cell carcinoma

• Atypical fibroxanthoma

image
Cutaneous Rhabdomyosarcoma
This cutaneous rhabdomyosarcoma (RMS) from the ear is a polypoid tumor with extensive infiltration of the dermis by hypercellular sheets of fairly uniform, small, hyperchromatic, ovoid cells.


image
Cutaneous Rhabdomyosarcoma at High Power
High magnification of a cutaneous RMS shows a nodular dermal proliferation of medium-sized, blue-staining, ovoid cells. A grenz zone separates the tumor from overlying epidermis.

image
Desmin Expression in Rhabdomyosarcoma
Desmin expression in RMS is typically diffuse and strong in the cytoplasm of the neoplastic cells. Cross striations may be highlighted.

image
Myogenin Expression in Rhabdomyosarcoma
Immunostaining for myogenin shows well-defined nuclear localization image. The proportion of nuclei expressing this marker varies. It is most widespread in alveolar RMS, with lesser degrees in embryonal and pleomorphic subtypes. Cytoplasmic staining is nonspecific and seen in many tumor types.


TERMINOLOGY


Abbreviations




• Rhabdomyosarcoma (RMS)


Definitions




• Malignant mesenchymal neoplasm arising in dermis &/or subcutis and showing variable differentiation toward skeletal muscle
image Cutaneous metastases or secondary involvement by deep primary tumor must be excluded

image Embryonal, alveolar, pleomorphic, and epithelioid types of RMS have been described as primary cutaneous tumors


CLINICAL ISSUES


Epidemiology




• Incidence
image However, primary cutaneous RMS is very rare

– Cutaneous metastases or secondary involvement of skin must be thoroughly excluded

• Age
image Bimodal age distribution
– Children and young adults
image Embryonal and alveolar types most common

– Older adults
image Pleomorphic and epithelioid types most common

• Sex
image M = F


Site




• May occur at any cutaneous site
image Including head and neck, trunk, extremities


Presentation




• Often presents as asymptomatic papule or nodule
image May cause pain

• Nonspecific clinical features
image Diagnosis may therefore be delayed


Treatment




• Complete surgical excision

• Chemotherapy &/or radiation


Prognosis




• Data limited due to small number of cases reported

• However, documented cutaneous cases prone to repeated recurrences and metastases (including to lymph nodes and lung)

• Overall mortality rate 36% in one small series


MACROSCOPIC


Size




• Usually 1-4 cm


MICROSCOPIC


Histologic Features




• May be confined to dermis, subcutis, or involve both dermis and subcutis
• May show ulceration of overlying skin

• Rhabdomyoblasts

image Cells with eccentric nuclei and variable amounts of eosinophilic cytoplasm

image Cytoplasmic cross striations may be visible

image Variable numbers and stages of differentiation

image Can be found in all RMS subtypes

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Apr 24, 2017 | Posted by in PATHOLOGY & LABORATORY MEDICINE | Comments Off on Cutaneous Rhabdomyosarcoma
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