Case: AP99
Contributor's Comment: All participants spot the diagnosis of lymphangiomyomatosis, although the involvement is actually quite subtle in this lung biopsy. To arrive at the correct diagnosis, the clinical history is very important. It is not uncommon to see spontaneous pneumothorax in young men, especially those with a tall-thin or Marfanoid habitus. In a young woman presenting with pneumothorax, lymphangiomyomatosis should certainly be a seroius consideration.

In some cases, the involvement is obvious on histologic examination. In other cases, as in this example, careful examination is required to identify the multiple small foci of involvement -- manifesting as areas with increase in spindly cells. These spindly cells differ from conventional smooth muscle cells in being often shorter, plumper and paler -- interspersed lymphatic/vascular spaces are found only in the larger foci. Immunostaining with HMB-45 antibody is very helpful to highlight the lesions.