Home > Extrapulmonary clear cell tumour
Definition
A tumour composed of epithelioid or spindle cells with clear or lightly eosinophilic cytoplasm and showing positivity for at least one or either HMB45 or Melan-A. Co-expression of melanocytic and myoid markers is required for morphologically atypical cases.
There is a strong female predominance, even for tumours outside the female genital tract. Very few cases are associated with tuberous sclerosis11.
Clear cell tumours are members of the family of PEComas and most commonly occur in the lung. Extrapulmonary sites include soft tissue8, base of skull11, trachea2, breast1, heart5, ligamentum teres, pancreas3, rectum5, bladder11, uterus4, vulva11 and perineum5.
The tumour may be circumscribed or infiltrative.
The tumour cells are clear or lightly eosinophilic and either epithelioid or spinded. They typically grow radially around blood vessels.
KL1 |
0/13 |
|
Pancytokeratin |
||
CK7 |
0/17 |
|
1/11, 1/13, 1/14, 4/45, 1/16, 1/17, 1/18, 1/19, 1/110, 22/2412 |
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Melan-A (MART-1) |
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Co-expression of (HBM45 or Melan-A) and SMA |
20/2412 |
|
9/1812 |
||
5/1712 |
||
NKI/C3 |
1/19 |
|
KBA.62 |
0/19 |
|
Neu-N |
0/17 |
|
1/19 |
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0/11 |
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1/17 |
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0/17 |
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0/17 |
||
0/17 |
||
0/110 |
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Differential diagnosis
Site |
Differential |
distinguishing features |
|
General |
clear cell carcinoma, glycogen-rich |
cytokeratin positive, HMB-45 negative |
|
clear cell carcinoma, lipid-rich |
cytokeratin positive, HMB-45 negative |
||
metastatic melanoma |
HMB-45 positive |
||
Abdomen |
GIST: PEComa may be CD117+ |
|
|
Kidney |
cytokeratin positive, HMB-45 negative |
||
Breast |
clear cell adenomyoepithelioma |
cytokeratin, actin and S-100 positive, HMB-45 negative |
|
Breast |
clear cell myoepithelioma |
cytokeratin, actin and S-100 positive, HMB-45 negative |
|
Base of skull |
chordoma, chondrosarcoma, meningioma, pituitary adenoma, haemangioblastoma |
|
|
Soft tissues |
clear cell sarcoma of soft tissue |
S-100 positive |
|
clear cell rhabdomyosarcoma |
desmin, myogenin, myoD1 positive |
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PAS positive |
|||
Prognosis
The presence of an infiltrating margin, mitoses, necrosis and nuclear pleomorphism are associated with metastatic behaviour.
References
7Lehman, N. L. (2004). "Malignant PEComa of the skull base." Am J Surg Pathol 28(9): 1230-2.
11 Hornick JL,Fletcher CD. PEComa: what do we know so far? Histopathology 2006; 48:75-82
This page last revised 25.5.2006.
©SMUHT/PW Bishop