The family of
tumors derived from mesenchymal perivascular epithelioid cells (so-called
PEComas) includes
angiomyolipoma,
lymphangioleiomyomatosis,
clear cell sugar tumor of the lung,
clear cell myomelanocytic tumor of ligamentum teres/falciform ligament, and abdominopelvic
sarcoma of perivascular epithelioid cells. These
tumors were characterized by coexpression of melanocytic (HMB-45) and muscle markers. MyoD1
transcription factor has crucial role in commitment and differentiation of mesenchymal progenitor cells to myogenic lineage.
Antibodies to MyoD1
protein (nuclear immunoreactivity) have been shown highly valuable adjuncts in the diagnosis of
rhabdomyosarcomas. To evaluate expression of the
transcription factor MyoD1 in
PEComas, we performed immunohistochemistry.
Monoclonal antibody 5.8A for MyoD1 was used on a series of cases of
formalin-fixed,
paraffin-embedded
angiomyolipoma (n = 19),
lymphangioleiomyomatosis (n = 3),
clear cell sugar tumor of the lung (n = 1), and abdominopelvic
sarcoma of perivascular epithelioid cells (n = 2). All cases showed strong granular immunostaining in the
tumor cell cytoplasm with the anti-MyoD1 antibody. Cytoplasmic reactivity was noted in the spindle cells, fat cells, and epithelioid cells. Nuclei were negative in all
tumors studied, and a clean background was obtained. Several normal and neoplastic human tissues have also been immunostained for MyoD1 without any positive cytoplasmic staining, with the exception of 2 alveolar soft part
sarcomas. Cytoplasmic immunostaining with
monoclonal antibody 5.8A for MyoD1 in
PEComas may correspond to cross-reactivity with an undetermined cytoplasmic
protein. Great caution should be exercised in interpreting the immunostaining results with anti-MyoD1 antibody 5.8A.