The clinical, morphological and immunohistochemical features of 15 cases of pulmonary lymphoproliferative disease are described. The diagnosis of primary pulmonary lymphoma was based in 13 cases on the demonstration of light chain restriction and in two cases on morphological characteristics. Many patients had a prolonged clinical course without significant clinical or radiographic deterioration, a feature associated with malignant lymphomas of mucosa-associated lymphoid tissue in other sites. Lymphoepithelial lesions were characteristic and malignant cells had the features of centrocyte-like cells, similar to those described in gastric and salivary gland lymphomas. Germinal centres were present in three cases: some were partially overgrown by centrocyte-like cells but residual polyclonal follicle centre cells and dendritic reticulum cells were still detectable. It is suggested that primary pulmonary lymphoma arises from centrocyte-like cells normally present in bronchus-associated lymphoid tissue. In addition to the malignant population, reactive follicles and polytypic plasma cells are frequently present and may prejudice interpretation of immunohistochemical features. In the light of these findings, cases previously diagnosed as pseudolymphoma or lymphoid interstitial pneumonia require careful assessment and the majority are, in reality, examples of primary pulmonary lymphomas.
Lymphangioleiomyomatosis (LAM) of the lung is a rare low-grade malignancy affecting primarily women of childbearing age. LAM is characterized by the proliferation of SMA and HMB-45 positive spindle-shaped and epithelioid cells throughout the lung in the form of discrete lesions causing cystic destruction and ultimately respiratory insufficiency. LAM occurs sporadically or in patients with tuberous sclerosis complex (TSC) and is etiologically linked to mutations in the TSC1 and TSC2 genes. Although LAM cells are known to express estrogen and progesterone receptors (ER and PR, respectively), their respective expression level was never determined. Therefore, here we measured the immunohistochemical expression of ERs and PRs in a large series of pulmonary LAM cases using the Aperio Spectrum Analysis Platform. Our case series comprised open lung biopsy specimens from 20 LAM patients and lungs explanted during the course of lung transplant from 24 patients. All cases were positive for ER and PR. PR expression was statistically significantly higher than ER in 80 % of the biopsies while ER predominated only in one case. Specimens from explanted cases of LAM had relatively fewer PR-positive nuclei. As a result, PR expression was significantly higher than ER in 38 % of the cases, whereas ER predominated in 33 %. Overall, PR expression predominated in 57 % of cases and ER in 21 %. These data indicate that PR frequently prevails over ER in pulmonary LAM. LAM is unusual in its high PR/ER ratio; other female neoplasms show a definite prevalence of ER. Our findings therefore warrant further study of PR function in LAM.
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