Moderator: Dr. Marisa Nucci
Uterine leiomyosarcoma with HMB 45 positive clear cell areas
W Glenn McCluggage, M.D.
Royal Group of Hospitals Trust
Belfast, Northern Ireland
A 60-year-old woman underwent hysterectomy for a fibroid uterus. Gross
examination revealed a 6 cm necrotic myometrial mass.
Uterine leiomyosarcoma with HMB 45 positive clear cell areas.
Uterine leiomyosarcomas may contain a component of epithelioid or clear cells, as well as the more
usual spindle cell elements. These epithelioid or clear cell areas may be minor in extent or may
predominate or be the exclusive component. The presence of clear cells which are HMB 45 positive within
a uterine mesenchymal neoplasm raises the possibility of a perivascular epithelioid cell tumour
(PEComa). However, it has recently been shown that undoubted uterine leiomyosarcomas may contain HMB 45
positive clear cells
A diagnosis of uterine PEComa should not be made based solely on
the presence of HMB 45 positive clear cells. The present case undoubtedly represents a uterine
leiomyosarcoma since typical spindle cell areas which were positive with smooth muscle markers were
In 1997, Bonetti et al  proposed a perivascular epithelioid cell (PEC) as the cell of
origin of epithelioid angiomyolipoma, some variants of lymphangioleiomyomatosis, clear cell sugar tumour
and more recently described neoplasms such as clear cell myomelanocytic tumour of the falciform
ligament/ligamentum teres and abdominopelvic sarcoma of perivascular epithelioid cells
These lesions are characterised by the presence of epithelioid cells which are HMB 45 and muscle marker
positive and may occur in patients with tuberous sclerosis complex. Recently it has been shown that a
subset of uterine mesenchymal neoplasms are composed focally, predominantly or exclusively of clear cells
that express HMB45. These neoplasms have been termed perivascular epithelioid cell tumour (PEComa) and
have also been described in other organs
In the seminal description of uterine PEComas,
the authors admitted that these neoplasms may be part of a spectrum with uterine epithelioid smooth
muscle tumours .
An epithelioid morphology is not uncommon in uterine leiomyosarcomas and this may be accompanied by
clear cell change, the clear cells potentially being HMB 45 positive
potential occurrence of uterine PEComa is acknowledged I feel more cases need to be studied before this
can be recognised as a specific entity within the uterus. It is noteworthy that HMB 45 positivity has
rarely been described in typical uterine leiomyomas and in normal myometrium . In addition,
a group of uterine mesenchymal neoplasms characterised by marked stromal hyalinisation and by epithelioid
cells without clear cytoplasm has been described which were positive with HMB 45 . The
authors speculated whether these represented epithelioid smooth muscle tumours or belonged to the
angiomyolipoma/PEComa group of neoplasms. However, it is admitted that occasionally seemingly bonafide
examples of uterine PEComa have been described, including one case where ultrastructural examination
revealed numerous premelanosomes . It has been suggested that melan A and micropthalmia
transcription factor expression is in favour of a PEComa but a recent study has shown that these markers
are not uncommonly expressed in uterine smooth muscle neoplasms . This study also
confirmed that uterine smooth muscle neoplasms, especially epithelioid smooth muscle tumours and
leiomyosarcomas, may be HMB45 positive.
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