Lymphangioleiomyomatosis, LAM

Lymphangioleiomyomatosis is a diffuse pulmonary infiltrate of short spindle cells, usually in association with cystic changes, occurring in women of reproductive age. LAM may also arise within lymph nodes, mediastinum, retroperitoneum and pelvis.

Epidemiology

This is rare condition. It most often occurs sporadically, but some cases are associated with tuberous sclerosis complex (TSC). 25-40% of women with TSC develop LAM. Renal angiomyolipomas occur in most women with TSC and in about half of the cases of sporadic LAM.

Clinical features

Patients show a slow progression to respiratory failure.

Histopathology

Lungs show widespread nodules composed of myoid cells, associated with dilated lymphatics and cystic change. The myoid cells have variably clear cytoplasm.

Immunohistochemistry

HMB-45

5/6¹

Melan-A

positive

Mitf

1/6¹

tyrosinase

0/6¹

Lymphangioleiomyomatosis may recur after lung transplantation: the recurrent LAM lesions are composed of recipient cells².

Prognosis

Without transplantation, the median survival is 8 to 10 years³.

References

¹ Miettinen M et al. Microphthalmia transcription factor in the immunohistochemical diagnosis of metastatic melanoma: comparison with four other melanoma markers. Am J Surg Pathol 2001;25:205-211.

² Bittmann I et al. Recurrence of lymphangioleiomyomatosis after single lung transplantation: new insights into pathogenesis. Human Pathol 2003;34:95-98.

³Hornick JL,Fletcher CD. PEComa: what do we know so far? Histopathology 2006; 48:75-82

This page last revised 1.2.2006.